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4 Potential Impacts to Health and the Environment Gold mines are industrial operations that can have significant impacts on the surrounding environment and local communities. At each stage in the life cycle of a mining operationâincluding exploration, development, mining, processing, closure, and reclamationâa variety of chemical and physical hazards can be encountered and adverse impacts to the landscape, ecosystems, and local communities can occur. As indicated in the introductory chapter, the committee interpreted the Statement of Task to confer an emphasis on human health and ecological concerns, rather than on the potential negative or positive societal and economic impacts associated with mining. Thus, these societal and economic impacts are not considered here, even though they are important to consider when completing site-specific environmental assessments prior to permitting. To ensure a thorough consideration of the potential impacts of gold mining on public health and the environ- ment, the committee focused on the impacts specified in the Statement of Task (âair and water qualityâ; see Box 1-3) and sought relevant information widely. This information included the concerns voiced by community members and stakeholders in public meetings or through written comments (see Box 4-1). Additionally, as there are few studies of environmental and health impacts specific to gold mining in Virginia, the committee considered case studies in other geographic settings that could be relevant to the Commonwealth. The committee evaluated this comprehensive catalog of potential impacts in the context of the Statement of Task (see Box 1-3), the geological and environmental context of Virginia (see Chapter 2), and the availability of reliable engineering controls to mitigate the risks (see Chapter 3) in order to identify specific impacts that deserved more detailed discussion. This chapter first summarizes some of the broad environmental impacts that could occur due to gold mining and processing in Virginia and then discusses individual impacts that can affect human health and the environment in more detail. BROAD DISCUSSION OF IMPACTS Although the study task emphasizes effects to public health, air, and water quality, the committee acknowl- edges that other concerns have been raised about potential impacts of commercial gold mining operations. For example, industrial-scale mining can disrupt the rural character of a region. Physical conversion of a site into a mine and associated facilities using heavy equipment can alter the viewscape and soundscape that are inherent parts of rural history and culture. Such disruptions, especially if sizable, can have undesirable consequences for property values, the future attractiveness of the region to people who value the character of rural areas, and the mental health of affected local communities. 91
92 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA BOX 4-1 Concerns from Citizens of Buckingham County In multiple open forums and in written comments, the committee heard public concerns that were expressed by dozens of community members, several community and environmental organizations, and business owners in areas of possible future mining in Buckingham County, Virginia. Although this report is concerned with potential impacts of gold mining in the entire Commonwealth of Virginia, most of the public input came from the citizens of Buckingham County and nearby areas owing to the more imminent concern there as a result of active exploration for gold deposits. Overarching concerns from these citizens included dewatering of aquifers and the effects on well water supply; pol- lution of local groundwater and surface water, including impacts to drinking water supplies, the James River, and the Chesapeake Bay; detrimental impacts to local fish, wildlife, and livestock; air pollution; adverse impacts to livelihoods of local residents; the inability to pass wealth and property on to future generations; and the loss of the rural character and lifestyle that is core to their communityâs identity and values. Community members expressed a strong connection to rural life, natural environments, and environmental stewardship. Many citizens who spoke with the committee come from families that have lived in the area for many generations or had moved to the area because of their desire to live in a rural community in close proximity to natural landscapes. Citizens were troubled by the possibility that an industry could come to the area for a relatively short period of time, extract its resources, disrupt the local rural character, close the mine, and potentially leave long-lasting impacts behind. These comments provide important context for understanding the concerns of citizens about the potential impacts of gold mining on their communities, even if the committee cannot evaluate many of these site-specific issues without more data on the deposit and proposed mining, processing, waste management, and reclamation plans. Physical conversion of land into gold mining operations also destroys or degrades natural habitat for flora and fauna, which may lead to decreased biodiversity. Virginia is home to an extraordinary diversity of plants and animals, and has several regions and streams that are recognized biodiversity hotspots (Roble, 2022). Across the Commonwealth, dozens of species are threatened or endangered and vulnerable to mining activities, to include bats, birds, amphibians, turtles, and freshwater fishes and mussels (Roble, 2022). Disturbance to these and other species can occur through the removal of trees and other vegetation, removal of topsoil overburden that releases organic carbon and nitrogen, installation of access roads, blasting and excavation of soil and rock, redistribution of water on-site, and transport of solutes and chemicals (e.g., metals, nitrates) in surface water and groundwater. Such adverse effects on habitat can affect local species diversity, but can also extend to migratory species, such as neotropical migrating bird species, that may rely on these habitats in Virginia for seasonal breeding activities or stopovers during longer-distance migrations. One prevalent impact of mining to natural habitat is the loss of soil and subsequent sediment and nutrient (e.g., nitrogen) loading into wetlands and waterways, because the removal of soils is necessary to allow construction of open pits, roads, facilities, ponds, tailings storage facilities, and waste rock piles. In some cases, the original soil may be lost if not appropriately salvaged prior to mining or stockpiled and maintained during operations. Even if soil material is salvaged for future use, re-creating the physical properties, microbial communities, and nutrient status of these original soils may not be feasible, even during land reclamation. As discussed in Chapter 3, open pit mines in Virginia are likely to be quite small, so these physical impacts to habitat would likely be spatially limited compared to larger mining operations in other portions of the United States. Although the committee does not cover these broad impacts in more detail below, they remain important considerations in the siting and development of a mine. The following sections discuss in more detail some of the most likely impacts of concern, as well as some that are unlikely to occur but were raised by the studyâs charge and concerned citizens. These include waterborne and sediment-associated contaminants and nutrients (acid rock drainage [ARD], metals, cyanide, nitrogen), tailings dam failures, water table depression, air emissions, and cumulative health effects. The discussion of these impacts draws from examples and lessons learned from other locations in the United States and abroad.
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 93 ACID ROCK DRAINAGE Reactive sulfide minerals can occur in the ore, on the walls of open pits or underground workings, or within the waste rock and tailings generated by mining and processing. When mining exposes sulfide-rich minerals, such as pyrite, to air and water, these minerals oxidize to form sulfuric acid and dissolved iron (see Boxes 2-1 and 2-3). This process is autocatalytic, meaning that once sulfide oxidation occurs, it tends to occur faster and is difficult to stop (see Box 2-3). Unless there is sufficient alkaline content (e.g., carbonates) within the mineralized zone or adjacent host rock to neutralize the acidity produced from sulfide oxidation, the resulting drainage water can create acidic runoff (referred to as acid rock drainage or acid mine drainage, hereafter ARD). ARD has low pH (often ranging between 2.0 and 5.0) and can contain high concentrations of sulfates and iron. Additionally, the acidic solution typically mobilizes a wide range of metals, such as lead, cadmium, copper, zinc, and other ele- ments, from the ore minerals and associated host rocks (metals and their associated health effects are discussed in the next section). Thus, ARD is a complex mixture of elements in a low-pH solution. The acid-generating potential of mines differs broadly depending on site-specific characteristics. Most of the recorded gold-quartz vein deposits in Virginia are relatively low in pyrite and have carbonate minerals (e.g., calcite and ankerite) that may neutralize some acid. Therefore, such deposits are not likely to be a high risk for generating extensive ARD. However, gold deposits in Virginia that are located in or in close proximity to massive sulfide deposits could pose higher risks of producing ARD if this material is exposed or disturbed during excavation (Hammarstrom et al., 2006; see Figures 2-3, 2-4, and 2-5). There is some evidence that ARD has been problematic for some mines in Virginia. For example, drainage from the historical Vaucluse Mine (see Chapter 2) has been reported to be extremely acidic (Virginia Energy, 2022e) and the Virginia Department of Energy (Virginia Energy) reported a brief period of ARD discharge from the active kyanite mine near Dillwyn in Buckingham County from February to April 2016 (Virginia Energy, 2022c). Conversely, waters associated with the low-sulfide Greenwood Gold Mine in Prince William County show pH values of 5.9 and 6.1 with no evidence of ARD (Seal et al., 1998). Without comprehensive, site-specific acid-base accounting and kinetic geochemical testing of relevant geologic materials, it is not possible to make a definitive assessment of the likelihood of ARD occurring in Virginia gold mines broadly. Thus, a robust site-specific analysis (e.g., quantity and reactivity of the pyrite exposed, presence of co-occurring minerals, bacterial activity) is necessary to determine the acid-generating potential of a particular deposit and its surroundings. Documents that describe best practices related to the prediction and treatment of acid rock drainage and metal leaching are described in Chapter 3. If present, ARD can be one of the most persistent and significant environmental problems associated with mining of sulfide-bearing deposits, including gold deposits. Because sulfide oxidation is autocatalytic, mines can continue to generate ARD long after mining operations cease unless appropriate precautions are incorporated into the mine design during operations and upon mine closure (see Chapter 3). For example, in Johannesburg, South Africa, tailings dumps of crushed rock from former gold mining operations have produced ARD for decades, pol- luting both ground- and surface water with dissolved metals, low pH, and salinity (Naicker et al., 2003). Similarly, the high-sulfide Summitville Mine in Colorado released extensive ARD for years, resulting in a cleanup process that has taken more than three decades (USGS, 1995). Closer to Virginia, the high-sulfide Brewer Gold Mine in South Carolina was designated as a Superfund Site due to its ARD production; the site has continued to produce large quantities of ARD since it was abandoned in 1999 (see Box 3-4). ARD is extremely toxic to plant and animal life due to its acidity, high specific conductance, and high con- centrations of heavy metals and other elements. The low pH of ARD is directly toxic to many animals, especially aquatic life (Fromm, 1980; Haines, 1981). Most freshwater fauna are intolerant of low pH because it can disrupt respiration, osmoregulation, growth, and reproduction of many species of invertebrates and fish (Fromm, 1980; Haines, 1981). Environmental impacts tend to occur when ARD contaminates streams and wetlands, either through direct surface runoff from mine sites, from acidic seeps, or from subsurface water that has hydraulic connectivity to surface waters (Johnson et al., 2017; McCarthy, 2011; Tutu et al., 2008). The acidity is eventually attenuated through a combination of neutralization and dilution within the groundwater system or downstream surface water. The high level of dissolved ions in ARD can increase the specific conductance and/or salinity of receiving waters to levels that are inhospitable for many freshwater organisms (CaÃ±edo-ArgÃ¼elles et al., 2013; Pond et al., 2008).
94 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA For example, groundwater polluted by ARD from South African gold mines that ultimately enters perennial streams can have specific conductance as high as ~4,000 microsiemens per centimeter (Î¼S/cm) (Tutu et al., 2008), an order of magnitude higher than that known to be detrimental to much freshwater life (EPA, 2011a). Likewise, seeps of ARD from the inactive Minnesota gold and silver mine in Colorado have specific conductance that fluctuates daily, seasonally, and after rainfall events between ~1,500 and 2,500 Î¼S/cm (Johnston et al., 2017). The seeps contribute to contamination of a nearby headwater stream (Lion Creek), causing the conductivity in the stream to rise to seasonal highs (~800 Î¼S/cm) sufficient to harm many sensitive freshwater fauna. High conductivity/salinity disrupts osmoregulation and ionoregulation in freshwater fauna, which can result in a myriad of adverse sublethal effects and death in some instances (Griffith, 2017; Reid et al., 2019). Finally, elevated concentrations of dissolved metals and other elements are common in ARD and have a wide array of adverse effects on organisms and ecosystems. Often some combination of these elements will co-occur in ARD, and cumulative exposure is likely. Ecological health risks and exposure pathways for key metals of concern are discussed in the next section. Collectively, low pH, high dissolved metals, and high conductivity/salinity can depress populations of aquatic organisms at all levels of the food web (including plants) and, as a result, entire aquatic communities can be deci- mated by ARD. This in turn has consequences for ecosystem-level processes like primary production and nutrient cycling. Unlike some of the other toxic constituents potentially released from gold mining that can be relatively short lived (e.g., cyanide), release of ARD containing metals and sulfates has long-lasting toxic effects. Although low-pH discharge can naturally attenuate in some circumstances based on local geochemical conditions, many constituents of ARD do not degrade (e.g., dissolved metals), but can precipitate or be transformed to other forms that can be more or less toxic to plants and animals. Thus, economically costly interventions (e.g., constructed wetlands, phytoremediation, neutralization with limestone) are typically needed to mitigate sources of ARD and remediate habitats impacted by ARD to prevent continual long-term damage. For example, it currently costs $1.18 million per year to treat ARD that is still being generated from tailings at the Brewer Gold Superfund Site in South Carolina (EPA, 2021d). In addition to harming the environment, ARD can impact drinking water that is sourced from the local aquifer or from downstream surface water intakes. Toxic metals dissolved in acid rock drainage can pose serious risks to human health, as discussed in the next section. Additionally, ARD can cause aesthetic impacts such as elevated concentrations of iron in drinking water that generates an unpleasant flavor and that can stain clothing and house- hold surfaces. Likewise, elevated sulfur compounds may lead to unpalatable taste or odor in the water, with the potential for gastrointestinal impacts (EPA, 2022n). METALS AND METALLOIDS Gold mining can be associated with the mobilization of numerous metals and metalloids,1 all hereafter referred to as metals. Although many metals can be solubilized and transported by ARD, others may be mobilized and released in the absence of ARD (Ashley, 2002; Ashley and Savage, 2001). There is considerable uncertainty involved in estimating the potential for the release of metals associated with gold mining across the Commonwealth. This is due to the variable spatial relationship of the primary quartz-hosted gold deposits with massive sulfide deposits that may have higher concentrations of metals of concern (see Chapter 2). With a few exceptions, the primary mecha- nisms and processes that can introduce metals into the environment are tailings dam failures, discharge of wastewater contaminated with metals, and the settling of metalliferous fugitive dust (see the âAir Emissionsâ section) into soils, wetlands, and surface waters (Donkor et al., 2005; Entwistle et al., 2019; Grimalt et al., 1999). Alternatively, metal mobilization could also occur following the disturbance of historical mine waste or materialsâfor example, the remobilization of mercury used for gold amalgamation in the past. Best practices for controlling erosion, mining- influenced water, and fugitive dust, as well as managing tailing storage facilities, are described in Chapter 3. Effective waste and water management of mines can greatly reduce the release of metals to the surround- ing environment. For example, following the abandonment of the Brewer Mine site in South Carolina in 1999, 1â A metalloid is an element with properties that are intermediate between those of metals and solid nonmetals or semiconductors.
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 95 stream sampling between 2002 and 2004 identified aluminum, barium, cadmium, cobalt, copper, iron, manganese, mercury, silver, zinc, and cyanide mean concentrations that were all above water quality standards (EPA, 2021d). However, following capture and treatment of the acid-producing seeps by a pump installed by the U.S. Environ- mental Protection Agency (EPA), the concentrations of metals were brought below water quality standards (EPA, 2021d; see Box 3-4). EPA reported that the site would be contributing 2,248 pounds/day of metals to the nearby creek if the pit water was not captured and treated (EPA, 2014b). Metals can exist in multiple oxidation states including metallic (valence zero), inorganic (charged cations combined with a variety of anions), and organic (e.g., methylmercury, tetraethyl lead, arsenobetaine, organotin compounds). The oxidation state of metals affects their fate, transport, and toxicity. Metals may sorb to sediments or precipitate in downstream wetlands and streams, generating contaminated sediments, or be distributed in floodplain soils following high-flow events. Depending on the chemical species of the element and local biogeo- chemical conditions, these precipitated metals can sometimes have low bioavailability and low toxicity. In other cases, bioavailable forms of metals deposited in sediments and soils can reach high concentrations that are toxic to benthic and soil organisms, respectively. Some organic forms, such as methylmercury, can bioaccumulate, while other organic forms, such as arsenobetaine and arsenocholine, are not bioaccumulative and are relatively nontoxic. Several metals can be solubilized during the cyanide leaching process and some metalâcyanide complexes are stable and can persist in tailings ponds. Key Metals of Concern for Plants and Animals Many metals are essential trace elements necessary for health of plants and animals, including copper, selenium, and zinc, but can become toxic at high concentrations or in complex mixtures. The primary routes of ecological exposures are through ingestion of metal-containing surface water, sediments, or food chain transfer, as well as across the gill epithelium in aquatic species (Clements et al., 2021). Table 4-1 lists those metals that may be associated with potential gold mining in Virginia; have plausible environmental exposure pathways to invertebrates, fish, and wildlife; and are inherently toxic, especially to aquatic fauna. Key Metals of Concern for Human Health The committeeâs approach to screening the primary metals of concern for human health associated with gold mining in Virginia is outlined in Figure 4-1. First, the committee identified metals of potential concern that were mentioned in the scientific literature associated with gold mining worldwide. Then, the committee reviewed the scientific literature on the exposure, epidemiology, and toxicology of these metals. This literature review included assessments by EPA, the Agency for Toxic Substances and Disease Registry, and the International Agency for Research on Cancer (IARC) of the World Health Organization. Metals that are essential trace elements with low inherent human toxicity (e.g., copper, chromium-III, selenium, zinc) and those with widespread environmental ubiquity or limited evidence of human health impacts (e.g., aluminum, boron, cobalt, nickel, silver, vanadium) were deprioritized for potential human health impacts. The geologic literature from Virginia, including Tables 2-2, 2-3, and 2-4, was then reviewed to determine if the remaining metals may be present in Virginiaâs gold mining areas (see Chapter 2 and Figure 4-1). Cadmium, lead, and thallium were noted in high concentrations in water samples immediately downstream of mined massive sulfide deposits (see Table 2-4), and as discussed in Chapter 2, similar deposits could be disturbed during mining of the low-sulfide, gold-quartz veins. Although antimony, arsenic, and mercury have not been noted in high con- centrations in Virginia ores (see Table 2-2), nor in downstream mine-influenced water (see Tables 2-3 and 2-4), the committee thought it was important to consider these elements given the limited data, their occasional asso- ciation with low-sulfide, gold-quartz vein deposits (Ashley, 2002), and/or their presence as legacy contaminants in historical mine sites. Other elements, like uranium, were deprioritized as they are not commonly associated with low-sulfide, gold-quartz vein deposits and the committee did not find evidence for elevated contents in the gold-bearing rocks of Virginia, nor in downstream mine-influenced water (Owens and Peters, 2018; Owens et al., 2013; Pavlides et al., 1982; Seal et al., 2002). Additionally, hexavalent chromium (Cr[VI]) was considered highly
96 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA TABLE 4-1â The Potential Adverse Effects of Selected Metals in Plants and Animals (Excluding Humans) Element Potential Adverse Effects in Plants and Animals Aluminum Toxic at high aqueous concentrations to aquatic animals, particularly fish, amphibians, and aquatic invertebrates. Disrupts osmo- and ionoregulation after both acute and chronic exposures. Particularly problematic in low-pH surface waters (Rosseland et al., 1990; Sparling and Lowe, 1996). Arsenic Acutely toxic to aquatic vertebrates and invertebrates, but lower concentration exposure and chronic toxicity are more common and can be associated with some accumulation in tissues, adversely affecting growth, reproduction, and survival. Can also disrupt food webs at low concentrations by influencing lower trophic levels like phytoplankton (Eisler, 2004; Sanders et al., 2019). Cadmium Adversely affects growth, reproduction, early development, and survival in fish, wildlife, and invertebrates. Can cause cancer. Freshwater aquatic species are generally more sensitive than birds and mammals. Can accumulate in some tissues (Eisler, 1985). Copper An essential element for both plants and animals. At high dissolved concentrations, copper is toxic to freshwater invertebrates and fish, but toxicity is greatly influenced by water chemistry (e.g., hardness, pH, alkalinity, etc.). Excessive copper can disrupt the nervous system, enzymes, and blood chemistry, ultimately impairing growth, reproduction, and survival. High concentrations in soils are toxic to plants (Rehman et al., 2019; Santore et al., 2001). Lead Highly toxic to plants and animals. Wildlife consuming excessive lead experience adverse neurological effects that can lead to death. Affects other tissues including kidneys and reproductive organs (Assi et al., 2016). Mercury Highly toxic to aquatic and terrestrial animals and can bioaccumulate and biomagnify in food webs, especially in its methylated form. Interferes with the nervous system, cardiovascular system, and reproduction (Eagles-Smith et al., 2018). Selenium Essential at low dietary concentrations, but toxic at slightly higher concentrations. Selenium is highly bioaccumulative but does not biomagnify in food webs. Egg-laying animals (fish, birds, and invertebrates) are particularly at risk of toxicity because selenium concentrates in eggs and is a potent teratogen (Janz et al., 2010). Thallium Highly toxic to terrestrial and aquatic animals and plants and can accumulate in tissues. In vertebrates it can induce reproductive abnormalities and metabolic disorders. In birds it can cause embryonic developmental abnormalities. In mammals, hair loss is a common symptom of sublethal exposure (Peter and Viraraghavan, 2005; USACHPPM, 2007). Zinc An essential element for enzymes in both plants and animals, but excessive zinc can be toxic. In mammals and birds zinc toxicity primarily affects the pancreas and bone. In fish, zinc disrupts gill tissue which can cause acute or chronic toxicity depending on aqueous concentrations. High concentrations in soils are toxic to plants (Eisler, 1993). NOTE: Metals such as cobalt, nickel, and vanadium are excluded because they are unlikely to be released from gold mining in Virginia in sufficient quantities to elicit toxicity (see Chapter 2). unlikely to be mobilized from Virginia mines given the low concentration of chromium in the host rock and the lack of a mechanism for the oxidation of trivalent chromium (Cr3+) to Cr6+ in ARD.2 Through these steps, the committee identified antimony (Sb), arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and thallium (Tl) as being priority metals of potential concern for human health due to their documented or potential association with Virginia ores or mine sites and their potential for toxicity. The primary routes of human exposure to these metals are through the ingestion of contaminated surface water, groundwater, biota, or crops. Contaminated soils can pose a health hazard if ingested, which is a pathway generally limited to children. The human health impacts of these metals are summarized in Table 4-2 and discussed in the following sections. 2â AtpH 2, ARD is in equilibrium with Cr3+ at lower redox potentials (1.07 Volts [V]) compared to the standard hydrogen electrode (SHE); Pourbaix, 1966), while Cr6+ predominates at higher potentials. The redox potential of ARD is controlled by the availability of dissolved oxygen and the redox equilibrium between Fe2+ and Fe3+, for which the standard redox potential is 0.771 V SHE (Pourbaix, 1966). Accordingly, there is no apparent mechanism for oxidation of Cr3+ to Cr6+ in ARD.
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 97 FIGURE 4-1â Schematic for the prioritization of metals. Initially all metals of concern found in association with gold deposits around the world were considered. Those metals that are essential trace elements and unlikely to cause human toxicity, those that are ubiquitous or have low inherent human toxicity, and those that are not expected to be present in relevant concentrations in Virginia ores and mine drainage were deprioritized. The remaining elementsâantimony (Sb), arsenic (As), cadmium (Cd), lead (Pb), and thallium (Tl)âwere identified as being of potential concern due to their documented presence in mine drainage from Virginia massive sulfide deposits or their potential association with Virginia gold-quartz vein deposits (Ashley, 2002). Mercury (Hg) may also be a concern in contaminated mine sites where it was used for processing in the past. Antimony Antimony can be a trace to minor constituent in sulfides, like pyrite (USGS, 2017a). While elevated concentrations of antimony have not been identified in downstream mine-influenced water in Virginia (see Tables 2-3 and 2-4), it has been documented in low-sulfide, gold-quartz vein deposits that are similar to those found in Virginia (Ashley, 2002). Additionally, antimony might be a concern if massive sulfide depositsâsometimes located near the low-sulfide, gold- quartz vein depositsâare disturbed during mining. EPA has established 0.006 mg/L antimony in drinking water as both the Maximum Contaminant Level Goal (MCLG) and the Maximum Contaminant Level (MCL; 40 CFR Â§ 141.62). The general U.S. population has exposure to low levels of antimony in food and water. An increasing number of human epidemiologic studies have been published in the past 15 years assessing the potential relationships between a range of health outcomes and various antimony concentrations in urine (ATSDR, 2019). The most consistent finding observed in more than one study was an association with high blood pressure (ATSDR, 2019). Antimony is predominantly found in the pentavalent oxidation state in water, but it can also be found in the trivalent oxida- tion state. Trivalent antimony is classified as probably carcinogenic to humans (Group 2A), whereas pentavalent antimony has been evaluated as not classifiable as to its carcinogenicity (Group 3; IARC, 2022). Arsenic Arsenic is a major element in the sulfide mineral arsenopyrite (FeAsS) and a trace to minor constituent in pyrite (Schellenbach and Krekeler, 2012). Arsenopyrite is rare in most gold deposits in Virginia (Pardee and Park, 1948), and elevated concentrations of arsenic have not been identified in downstream mine-influenced water in
98 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA TABLE 4-2â The Potential Adverse Effects of Selected Metals in Humans Element Potential Human Health Effects Antimony Lower doses have been correlated with increased blood pressure (ATSDR, 2019). Health effects at higher doses unlikely to be relevant to gold mining include respiratory effects, gastrointestinal symptoms, joint and muscle pain, neurodevelopmental effects, risk of diabetes, and electrocardiogram changes. Trivalent antimony is classified as probably carcinogenic to humans (Group 2A), whereas pentavalent antimony has been evaluated as not classifiable as to its carcinogenicity (Group 3; IARC, 2022). Arsenic Exposure is linked to circulatory system, skin, and neurologic effects; lung, bladder, and skin cancer; type 2 diabetes; and other adverse outcomes (ATSDR, 2007). Arsenic causes lung, bladder, and skin cancer and is classified as a Group 1 carcinogen (IARC, 2012a). Cadmium Associated with neurodevelopmental toxicity in children and renal toxicity in children and adults (ATSDR, 2012). Cadmium causes lung cancer and is classified as a Group 1 carcinogen (IARC, 2012b). Lead Associated with a range of health effects in fetuses, children, and adults. Lead can have adverse effects in almost every organ system, with particular effects on brain health and development. Lead bioaccumulates, is deposited in bone, and can be slowly released over time to affect various organs (ATSDR, 2020). Inorganic lead compounds are classified as probably carcinogenic to humans (Group 2A), whereas organic lead compounds have been evaluated as not classifiable as to their carcinogenicity (Group 3; IARC, 2006). Mercury Exposure leads to neurologic, cognitive, and neurodevelopmental effects, and there is some evidence for cardiovascular effects. Exposure is of greatest concern for pregnant women and their fetuses. Methylmercury bioaccumulates in fish and is a risk after ingestion (ATSDR, 2022). Methylmercury has been classified as possibly carcinogenic to humans (Group 2B), whereas inorganic mercury compounds have been evaluated as not classifiable as to their carcinogenicity (Group 3; IARC, 1993). Thallium Low doses for longer duration are associated with obesity, impaired thyroid function, autism spectrum disorders, adverse pregnancy outcomes, measures of oxidative stress, gestational diabetes, and others (Campanella et al., 2019). Virginia (see Table 2-4). Nevertheless, the committee considered arsenic since it is documented to occur in some low-sulfide ore deposits (Ashley, 2002; Schellenbach and Krekeler, 2012) and might be a concern if nearby mas- sive sulfide deposits are disturbed during mining. It is also possible that arsenic could be mobilized in aquifers (Alpers, 2017; Peters and Blum, 2003; Verplanck et al., 2008) if mining triggers changes in hydrologic conditions. For example, increases in dissolved oxygen in groundwater due to water table changes can oxidize arsenopyrite and pyrite and release arsenic into solution as As3+ and As5+ species. Alternatively, arsenic sorbed to Fe-Mn oxyhy- droxide minerals in aquifer materials can be released into solution by reductive dissolution of the Fe-Mn minerals (Fendorf and Kocar, 2009; Peters and Blum, 2003). Compilations of arsenic data from well water in Virginia show that 15 to 23 percent of well water samples have arsenic concentrations over 5 Î¼g/L, but most well water samples with elevated arsenic were found in the Culpeper Basin and other Triassic sedimentary basins that do not host gold (VanDerwerker et al., 2018). These limited data leave considerable uncertainty regarding the possible mobilization of arsenic in aquifers following water table changes in the gold-bearing regions of Virginia. EPA has established 0 mg/L arsenic in drinking water as the MCLG and 0.010 mg/L as the MCL (40 CFR Â§ 141.62). The most common route for human exposure to arsenic is through drinking water containing geologically derived arsenicâit has been estimated that more than 2 million Americans use drinking water wells with arsenic levels in excess of drinking water limits (USGS, 2019). Arsenic is tasteless, odorless, and colorless and has been linked to circulatory system, skin, and neurological effects; type 2 diabetes; and other adverse outcomes (ATSDR, 2007). Arsenic causes lung, bladder, and skin cancer and is classified by EPA and the IARC as a known human carcinogen (Group 1; IARC, 2012a). Long-term ingestion of arsenic has been associated with increased risk of heart disease, skin abnormalities, adverse pregnancy outcomes, and diabetes (ATSDR, 2007, 2020; BrÃ¤uner et al., 2014; Ettinger et al., 2009; Farzan et al., 2015a,b; Navas-Acien et al., 2008). Cadmium Cadmium can be hosted at minor to trace concentrations in sphalerite, chalcopyrite, galena, and pyrite (Schwartz, 2000). These sulfides are commonly found in massive sulfide deposits, such as those that are sometimes
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 99 near Virginiaâs low-sulfide gold deposits. In South Carolina, the Haile Gold Mine has been fined for cadmium discharges to surface waters (The State, 2021), and elevated cadmium concentrations have been observed in mine-influenced water downstream of Virginiaâs massive sulfide deposits (see Table 2-4). EPA has established 0.005 mg/L cadmium in drinking water as both the MCLG and the MCL (40 CFR Â§ 141.62). Absorption of significant levels of cadmium from water sources can result in a number of adverse health outcomes. Cadmium is associated with neurodevelopmental toxicity in children, has a long retention time in the kidney, and is a known cause of renal toxicity in children and adults as a function of cumulative dose (ATSDR, 2012; Satarug, 2018). Cadmium is often found with other metals in well water, some of which are also renal toxi- cants (e.g., lead; Rehman et al., 2018). This explains why some authors are cautious in solely attributing observed chronic renal effects to cadmium (Butler-Dawson et al., 2022; Herath et al., 2018; Kaur et al., 2020; Wasana et al., 2016). Cadmium also causes lung cancer and is classified as a Group 1 carcinogen (IARC, 2012b). Lead Galena (PbS) is reported as a common trace mineral in many Virginia gold deposits (Schellenbach and Krekeler, 2012), including the London and Virginia Mine, Moss Mine, and Vaucluse Mine gold deposits (see Chapter 2). In addition, elevated lead concentrations have been observed in mine-influenced water downstream of Virginiaâs massive sulfide deposits (see Table 2-4), which are sometimes located in the vicinity of low-sulfide, gold-quartz veins in Virginia. Finally, lead is sometimes used as an additive to assist in the gold dissolution pro- cess (Kyle et al., 2011, 2012). EPA has established 0 mg/L lead in drinking water as the MCLG and 0.015 mg/L as the MCL action level, which is the level at which additional steps must be taken (40 CFR Â§ 141.62). The U.S. Centers for Disease Control and Prevention has repeatedly lowered the threshold at which blood lead levels are considered to be of concern in children from 60 Î¼g/dL3 to 5 Î¼g/dL over the past 40 years, although it is generally agreed that there is no safe level of lead exposure for children (AAP, 2021). Lead is a human toxicant with well-documented health effects in fetuses, children, and adults. Toxicity can be found in almost every organ system, including the central nervous system and peripheral nervous system, as well as the reproductive, cardiovascular, hematopoietic, gastrointestinal, and musculoskeletal systems. Inorganic lead compounds are classified as probably carcinogenic to humans (Group 2A), whereas organic lead compounds have been evaluated as not classifiable as to their carcinogenicity (Group 3; IARC, 2006). Lead poisonings from gold mining have resulted in tragic events internationally. Lead exposure due to artisanal gold mining in northern Nigeria (Lo et al., 2012; Tirima et al., 2016) was the largest known occurrence of lead poisoning in history (CDC, 2016). This setting was unique in that the gold-containing ore contained a vein with more than 10 percent lead, and occupational and public health safeguards were lacking. Given the more robust regulations in the United States, the committee concluded that the unique features of this extreme example are not relevant to gold mining in Virginia. Mercury Mercury is unique among the metals considered by the committee in that it has both a natural source from sulfide ores (including some ores mined for gold, such as those at the McLaughlin Mine in California) and an anthropogenic source from the historical use of it for amalgamation of gold. Although the mercury content of gold deposits in Virginia is expected to be low (see Chapter 2), the limited number of analyses leaves significant uncertainty in estimating the concentrations of mercury. In addition, mercury was widely used in Virginia in the 1800s to amalgamate gold at mine sites. Large quantities of mercury were often lost during the gold mining pro- cess, and previous gold mining areas and downstream rivers are often highly contaminated with mercury (e.g., in the Sierra Nevada foothills, California; Saiki et al., 2010). Because metallic mercury is relatively stable in the environment, it can be found in high concentrations in stream sediments and soils hundreds of years after mining activities have ceased (see Box 1-1). Sampling of the distribution and occurrence of mercury at historical gold 3â A deciliter (dL) is one-tenth of a liter.
100 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA mining sites in Virginia is limited. Hammarstrom et al. (2006), however, reported up to 1.5 mg/kg of mercury in the pond sediment at the site of the Mitchell Gold Mine. Up to 40 mg/kg of mercury in soil and 3.7 mg/kg of mercury in sediment was reported near the Greenwood Gold Mine (Seal and Hammarstrom, 2002; Seal et al., 1998). Elevated mercury concentrations in stream sediments have also been reported near the Vaucluse Mine (Virginia Energy, 2022e). If a new mine were established on the site of a historic mine where mercury was used to amalgamate gold, the legacy mercury could be excavated and re-released into surface waters, unless it is fully captured and removed for processing (see Box 3-2). The general U.S. population is often exposed to mercury from the consumption of fish, other seafood, and rice, and via dental amalgams. Based on 2016 data from the National Health and Nutrition Examination Survey, the general U.S. population has been estimated to have a geometric mean total blood mercury level of 0.81 Î¼g/L. EPA has established 0.002 mg/L mercury in drinking water as both the MCLG and the MCL (40 CFR Â§ 141.62), but drinking water is generally considered a minor source of mercury exposure (WHO, 2005). Mercury can be found in many forms, including metallic/elemental mercury (Hg0); oxidized, inorganic diva- lent mercury (Hg2+); and organic, mono-methyl mercury (MMHg; Morel et al., 1998). The production of MMHg from Hg2+ occurs in low-oxygen environments (wetlands and lake/river bottom sediments) mainly by sulfate- and iron-reducing bacteria (Morel et al., 1998). In aquatic systems, MMHg is taken in by algae and subsequently transferred up the food web to zooplankton, small forage fish, and finally large predatory fish in lakes and rivers. Thus, it is often larger/older fish feeding at high trophic levels that have the highest levels of MMHg. Consump- tion of high-trophic-level fish caught either for sport or as a needed source of protein (most often by people with low incomes) can lead to unsafe levels of exposure to MMHg. Numerous rivers and lakes in and downstream of historically gold-producing counties in Virginia are under fish consumption advisories for mercury. Water bodies with fish consumption advisories that are in historically gold-producing counties include Lake Gordonsville in Louisa County; Nottoway River in Dinwiddie County; Motts Run Reservoir in Spotsylvania County; Dan River in Pittsylvania, Halifax, and Mecklenburg Counties; Roanoke River in Pittsylvania, Campbell, Halifax, Charlotte, and Mecklenburg Counties; and Kerr Reservoir and Lake Gaston in Mecklenburg County (VDH, 2022a). For some of these water bodies, the point source of mercury is from industrial operations, but in others, the source is unknown but is likely a combination of legacy mines, industrial inputs, and atmospheric deposition. For example, samples collected by the Virginia Department of Environmental Quality from streams at the Vaucluse Mine site indicated that mercury levels in fish tissue (up to 0.47 mg/kg) were above background levels and very close to the current action levels for a fish consumption advisory in Virginia (0.5 mg/kg). The report concluded that mercury from the historical mine site was entering the aquatic food chain (Holmes, 2022). Although fish consumption advisories due to mercury can help protect public health, local communities that rely on fish for sustenance lose valuable protein from their diet when fish is unsafe to eat. Additionally, the sport fishing industry in Virginia is estimated to generate $1.3 billion annually with 800,000 anglers participating each year (Virginia DWR, 2022), highlighting the potential economic consequences of fish advisories caused by mercury pollution. Mercury is a potent neurotoxicant in each of its environmental forms. Although Hg0 and Hg2+ can be hazardous, toxic levels are generally limited to occupational exposures. MMHg is, however, more toxic than other forms of mercury and, as described above, is strongly bioaccumulated and biomagnified by about tenfold in concentration for each trophic level. Studies of MMHg report consistent neurologic, cognitive, and neurodevelopmental effects; some evidence for cardiovascular effects; and the possibility of other developmental effects (e.g., structural malfor- mations). Many of these effects are of greatest concern for pregnant women and their fetuses, although people can potentially be adversely affected at any point in the lifespan. Animal studies also raise concern about renal effects (ATSDR, 2022). Methylmercury has been classified as possibly carcinogenic to humans (Group 2B), whereas inor- ganic mercury compounds have been evaluated as not classifiable as to their carcinogenicity (Group 3; IARC, 1993). Thallium Thallium can be hosted as a trace metal in pyrite, galena, and sphalerite and, therefore, could be a potential metal of concern if nearby massive sulfide deposits are disturbed during the mining of Virginia low-sulfide, gold-quartz veins. The Haile Gold Mine was fined for discharging thallium into surface waters (The State, 2021)
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 101 and one sample of mine-influenced water in Virginia had elevated thallium concentrations (see Table 2-4). Addi- tionally, thallium may be elevated in the host rock adjacent to low-sulfide, gold-quartz veins deposits (Ashley, 2002), such as the deposits in Virginiaâs gold-pyrite belt and the Virgilina district. EPA has established 0.0005 mg/L thallium in drinking water as the MCLG and 0.002 mg/L as the MCL (40 CFR Â§ 141.62). Thallium has two primary oxidation states, Tl+ and Tl3+; both are toxic but Tl3+ is likely more so (Rickwood et al., 2015; Zhuang and Song, 2021). Tl+ is the most common species in surface waters. In the body, Tl+ competes with potassium (K+) and is widely distributed, including to heart and brain cells. Because of its similarity to potas- sium, thallium concentrates in tissues with high potassium concentrations and can inhibit potassium-dependent processes. Of increasing concern is the toxicity of thallium at lower doses for longer durations, as can be found in the consumption of drinking water containing thallium through natural or anthropogenic contamination (Biagioni et al., 2017; Campanella et al., 2019). A growing epidemiologic literature has associated increased levels of thal- lium in urine and blood with a number of adverse health outcomes, including obesity, impaired thyroid function, autism spectrum disorders, adverse pregnancy outcomes, measures of oxidative stress, gestational diabetes, and others (Campanella et al., 2019). Thallium contamination of drinking water has been highlighted as an emerging environmental health issue that requires more attention. A growing number of studies in the past 10 years have identified putative health effects at contaminant levels far below the current EPA MCL (Campanella et al., 2019). CYANIDE Since the late 1800s, cyanide leaching has been one of the primary mechanisms for recovering gold from ore. Today, it has completely replaced the use of mercury in gold mining both in the United States and in other high-income countries. Cyanide, primarily in the form of dilute sodium cyanide solutions, is typically applied to mined and crushed ore using either tank or heap leaching techniques (see Chapter 3). Gold is then removed from the resultant gold-bearing solutions using zinc or activated carbon, and the remaining cyanide solution is recycled to leaching. Any waste materials containing cyanide typically undergo cyanide destruction treatment during operation or prior to final mine closure (EPA, 1994c). Although some alternatives to cyanide leaching have been developed, none are as widely available, efficient, or as economical as cyanide-based methods. However, cyanide is extremely toxic and must be managed carefully to avoid harm to human health and the ecosystem (see Box 3-3). Accidental releases of cyanide from gold mining into the environment have occasionally harmed humans and resulted in mass mortality of fish and other wildlife (Cleven and Van Bruggen, 2000; Donato et al., 2017; Eisler et al., 1999; Moran, 1998, 1999). Despite successful use and improved management of cyanide at mines (described in Chapter 3), its potential to cause considerable harm if mismanaged understandably makes it one of the most significant concerns of the public. Cyanide is extremely toxic to humans, fish, wildlife, invertebrates, and to a lesser extent other life such as certain aquatic plants and algae. In animals, cyanide blocks oxidative energy metabolism by disrupting a critical enzyme (cytochrome oxidase), which then deprives cells of energy, results in calcium imbalances, and ultimately causes cell death (Solomonson, 1981). As a result, cyanide toxicity often manifests as disruptions to the cardio- vascular and nervous systems (Borowitz et al., 2005) because heart and brain tissue are particularly reliant on oxygen and energy for proper function and are also susceptible to changes in electrical activity important in cel- lular signaling. Symptoms of cardiovascular disruptions following cyanide poisoning include slowed heart rate, abnormal heart rhythms, and heart failure (Borowitz et al., 2005). Neurotoxic effects of cyanide can present as behavioral abnormalities, seizures, impaired vision, and loss of consciousness. Other manifestations can include vomiting and shortness of breath, and, at high doses, death within minutes (Borowitz et al., 2005). Cyanide spills pose acute risks to human health and the environment, but minimal long-term risks because cyanide does not bioaccumulate in animal tissues and tends to break down in the environment quickly. These are among the reasons that cyanide has replaced mercury amalgamation as the preferred method of gold extraction in many places around the world (Veiga and Meech, 1999). Cyanide does not accumulate in animal tissues because low doses are readily detoxified and metabolized by animals and acute exposure to high doses are fatal, making transfer via the food chain negligible in most situations (Eisler, 1991). Free cyanide (HCN and CNâ) is its most toxic form (Gensemer et al., 2006), but this form naturally breaks down over time by photodegradation, chemical
102 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA oxidation, volatilization, and microbial processes (Dzombak et al., 2005; Ebbs et al., 2005). Cyanide also readily binds to a variety of metals (e.g., zinc, cadmium, iron, copper, mercury, cobalt) to form relatively nontoxic metal- locyanide complexes,4 which can persist for longer periods of time but are slow to release toxic, free cyanide into solution (Borowitz et al., 2005; Dzombak et al., 2006). Cyanide is not typically bioavailable in sediments and soils (Gensemer et al., 2006) and does not persist for extended periods of time in these environmental media (Eisler et al., 1999). Thus, when cyanide is accidentally released from mining operations, it does not typically persist in soils and sediments for extended periods of time, and degrades in water within days to weeks (Eisler et al., 1999). However, these degradation processes can be slow in holding ponds due to the high concentrations of cyanide and water chemistry in these settings (Simovic and Snodgrass, 1985), so gold mines often employ a variety of chemical (e.g., alkaline chlorination), ultraviolet light, and microbial treatments to accelerate the degradation of cyanide on-site. Cyanide toxicity among human populations near gold mining operations is rare. Cyanide can be toxic to humans via direct inhalation and contact, but ingestion of cyanide-contaminated water is the primary exposure route (e.g., Pannier, 2020). When not stored in carefully controlled basic solutions, cyanide can convert to hydro- gen cyanide gas, which can be inhaled and is extremely toxic to humans (The Canadian Press, 2016; International Cyanide Management Code, 2022; Peiyue, 2021). However, this impact is primarily an occupational concern and can be managed using best practices, such as the International Cyanide Code (see Chapter 3). In contrast to rare gaseous exposures, aqueous cyanide exposure has occasionally resulted from mishandling of cyanide at gold mines, such as a large spill from a truck carrying NaCN in Kyrgystan in 1998 that resulted in contamination of surface drinking water, which produced conflicting reports regarding fatalities and thousands of illnesses (Cleven and Van Bruggen, 2000; Moran, 1998, 1999). In addition, probable low-level aqueous exposures to cyanide in communities living near gold mines have been linked to headaches, dizziness, eye irritation, and skin irritation in Malaysia, and in some cases these symptoms were associated with biomarkers of exposure to cyanide (i.e., urinary thiocyanate; Hassan et al., 2015). The committee could not identify any publications that described accidental release of cyanide from modern gold mining that affected drinking water in the United States, but the potential exists in circumstances where communities rely on surface water. For example, the cyanide release at the Brewer Mine in South Carolina was prevented from contaminating local drinking water supplies by the rapid response of local authorities (Jim McLain, personal communication, 2022). In contrast to rare human exposures, the potential for ecological impacts is far greater if proper precautions are not in place. Historically, wildlife exposures to cyanide have occurred on-site in extraction and tailings ponds, as well as small pools of cyanide solution on top of ore heaps (Henny et al., 1994). In addition, accidental release of cyanide from mine sites can have catastrophic consequences for downstream ecological communities. The vast majority of documented cases of cyanide poisoning of fish and wildlife linked with mining activities (both on and off mine sites) involve acute aqueous exposure. Prior to the relatively widespread adoption of international best practices such as those outlined in the Inter- national Cyanide Code (see Chapter 3), ponds containing cyanide-bearing leach solutions often attracted wildlife to bathe, drink, or reproduce. At gold mines in the western United States, diverse species of birds, amphibians, reptiles, and mammals have been found at cyanide gold leaching ponds (Clark and Hothem, 1991; Griffiths et al., 2014). Birds are particularly vulnerable, as they are attracted to even small pools of open water. For example, birds comprised about 90 percent of the dead wildlife found near cyanide leach ponds near gold mines in California, Nevada, and Arizona (Clark and Hothem, 1991). Thousands of bird deaths involving waterfowl and migratory species in Nevada were attributed to birds drinking, bathing, and resting in ponds at gold mines containing high cyanide concentrations (Henny et al., 1994; Hill and Henry, 1996). Observations at these sites indicate that some birds die on-site quickly, but others fly off-site after swimming and drinking cyanide-polluted water, suggesting that on-site counts of dead birds may underestimate the actual impact of improperly managed cyanide ponds (Henny et al., 1994). The risk to birds extends beyond cyanide ponds, as the small pools of cyanide solution that may form on top of heaps at mine sites also attract birds and cause mortality (Donato et al., 2007; Henny et al., 1994). Fortunately, adoption of best practices that are typically required during the mine permitting stage has minimized many of these problems. Common best practices include cyanide treatment to decrease concentrations 4â Including weak acid dissociable cyanide complexes and strong acid dissociable cyanide complexes.
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 103 (often to <50 mg/L weak acid dissociable cyanide) prior to release into surface impoundments to decrease the risk of acute toxicity to wildlife. Likewise, a variety of deterrents (e.g., exclusion netting, pond covers, floating balls, noise/light) have been developed to deter wildlife from accessing surface water at these facilities. Similar risks of exposure would need to be carefully managed in the gold pyrite belt of Virginia, especially in light of its high biodiversity and population densities of wildlife. In Virginia, amphibians, migratory songbirds, waterfowl and waterbirds, and bats are among the groups of wildlife that depend on open surface water and should be deterred from using ponds containing cyanide. Because the toxicity of cyanide is not well studied in many of these species but some of them are known to be highly sensitive to environmental pollutants (e.g., amphibians), deterrents are critical for minimizing possible on-site exposure to cyanide. In addition to on-site exposures, accidental releases of cyanide have resulted in catastrophic consequences for downstream ecosystems (e.g., streams and wetlands; see Box 3-3). In general, aquatic animals are particularly sensitive to cyanide poisoning because they are often completely immersed in water, even exposing their sensitive respiratory structures (i.e., gills) to dissolved cyanide. Fish kills are often the most conspicuous effect of cyanide release because fish are particularly sensitive to cyanide toxicity (Eisler, 1991). Additionally, dead fish are more easily observed than other species such as birds that can move off-site before dying and aquatic invertebrates that are simply less conspicuous. For example, cyanide release from a mine in Canada killed more than 20,000 steelhead trout (Leduc et al., 1982). In addition to acute mortality, long-term exposure to sublethal levels of cyanide can have consequences for fish and freshwater communities. Most notably, nonlethal exposure to cyanide has long been known to impair fish reproduction (Leduc, 1981, 1984; Leduc et al., 1982; Lesniak and Ruby, 1982; Ruby et al., 1986). Other sublethal effects of cyanide on fish include behavioral abnormalities, poor swimming performance, and reduced growth, all of which have implications for survival (Eisler et al., 1999). These long-term sublethal impacts are less common than acute mortality events given that cyanide tends to break down in the environment quickly. Instead, the long- term effects of cyanide on the environment likely relate primarily to the pace of ecological recovery processes. For example, cyanide released from a gold mine in Japan following an earthquake killed all biota in a stream for approximately 10 kilometers. However, within days cyanide was no longer detectable in the water and within 6 months local plant, invertebrate, and fish species were recolonizing the impacted region of the stream (Yasuno et al., 1981). At the Brewer Mine in South Carolina, taxa richness and abundance of aquatic invertebrates were reduced for months downstream of the point of cyanide release but other signs of recovery were beginning to become evident months after the spill (Shealy Environmental Services Inc., 1991; see Box 3-3). NITROGEN As discussed in Chapter 3, operators often use a mixture of ammonium nitrate and fuel oil for blasting during mining. Proper detonation will ensure the blasting product is wholly consumed to produce gases such as CO2, N2, and H2O (Martel et al. 2004). However, nonideal blasting practices (e.g., wet conditions) may produce more toxic gases such as CO, NO, and NO2, and estimates for the mass of explosive nitrogen remaining after detonation ranges from 0.2 percent for near-ideal conditions to up to 28 percent in nonideal conditions (Bailey et al., 2013; Brochu, 2010; Morin and Hutt, 2009; Pommen, 1983). Residual nitrogen compounds and undetonated ammonium nitrate may occur on the surfaces of the host rock (in pit or underground mines) and the blasted rock, and it may be processed as ore or disposed as waste material. Undetonated ammonium nitrate and the ammonium ion (NH4+) are readily soluble in water and could be further mobilized by runoff, infiltrating water, or process solutions. Without implementing appropriate strategies for the management and treatment of this water, poor hydrologic containment may lead to loading of nitrogen in surface runoff and groundwater discharge mostly as nitrate species (NO3â), but also as ammonia (NH3) and to a lesser extent nitrite (NO2â) (Brochu, 2010). Depending on the size of a mining operation and the frequency of blasting, hundreds to tens of thousands of kilograms of ammonium nitrate may be used at a site. This can lead to a substantial amount of nitrogen-laden effluent that can exceed water quality criteria. Several mines around the United Statesâincluding the Buckhorn Mine in Washington state and the Jamestown, McLaughlin, and Royal Mountain King Mines in Californiaâhave received violations from the discharge of excessive nitrogen that range from 25 to 600 mg/L nitrate (5.6â135.5 mg/L
104 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA nitrate as nitrogen) and 10 to 40 mg/L ammonia (Brochu, 2010; Maest, 2022). Concentrations will be most elevated proximal to the mine site, as movement downstream or down-gradient will result in attenuation and dilution of the nitrogen levels. Virginia has set the surface water quality criteria for the protection of human health as 10 mg/L for nitrate as nitrogen (9VAC25-260-140) and has also set the groundwater standards for the Piedmont and Blue Ridge regions as 5 mg/L nitrate and 0.025 mg/L for nitrite and ammonia (9VAC25-280-50). Although there are no surface water quality criteria for nitrate for the protection of aquatic life, acute and chronic water quality criteria have been established for ammonia in order to protect freshwater mussel species and the early life stages of fish (9VAC25-260-155). These acute and chronic water quality criteria for ammonia are determined by site-specific pH and temperature conditions, with values ranging from 0.27 to 51 mg/L and 0.08 to 4.9 mg/L, respectively (9VAC25-260-155). Excessive nitrogenous compounds in water can pose health risks to humans and the environment. Although ammonium ion toxicity is low, it is readily converted to nitrate in aquatic systems (Camargo et al., 2005), which can affect aquatic life or pose a health hazard to humans (Brochu, 2010). For example, high nitrates in drink- ing water can induce production of methemoglobin, a form of hemoglobin that cannot effectively transport and release oxygen to tissues, and infants less than 6 months of age are particularly at risk for this condition. When methemoglobin is produced in high quantities it can lead to methemoglobinemia, a syndrome of inadequate tissue oxygenation. Public health actions and the water quality criteria have been established by EPA (10 mg/L nitrate as nitrogen) to protect infants, the most sensitive population (EPA, 2022e; Minnesota Department of Health, 2018). In addition, the presence of excessive nitrate in surface water can promote algal blooms, growth of harmful cyanobacteria, and eutrophication. This is especially true when excessive nitrogen occurs in conjunction with an excess of other elements such as phosphorous and iron (Wurtsbaugh and Horne, 1983; Xiao et al., 2021a), the latter of which can occur in very high concentrations in mining effluent and runoff. Because iron is often a limit- ing factor for the growth of phytoplankton, its release in conjunction with excessive nitrogen can accelerate algal growth. Eutrophication of surface waters depletes dissolved oxygen and over time also decreases pH, which can both be lethal to invertebrates and fish, sometimes resulting in anoxic zones (also known as âdead zonesâ) and fish kills. Nitrogen loading from mining poses concerns to aquatic habitats near mining sites but also potentially contributes to loads that have consequences for more distant habitats, such as the Chesapeake Bay. A multi-state effort is under way to restore the habitats of the Chesapeake Bay, with a major focus on reducing loads of nitro- gen, phosphorus, and sediment to improve conditions for the bayâs aquatic life. Total maximum daily loads of nitrogen, phosphorus, and sediment for each state and each watershed have been established by EPA to reach the restoration goals (see also Chapter 5), and Virginia has worked aggressively to reduce its nutrient loads to meet the restoration targets (see Figure 4-2). TAILINGS STORAGE FACILITIES FAILURE AND TAILINGS RELEASE Some gold mining operations produce large amounts of slurry effluents, called tailings (Adler and Rascher, 2007). Tailings, which can contain a wide range of metals, are often stored in impoundments behind perimeter dikes (i.e., in tailings storage facilities [TSFs]). Although numerous best practices designed to safely retain these materials are presented in Chapter 3, TSFs can occasionally fail, releasing toxic materials downstream into streams and rivers with negative effects on natural ecosystems and on human health. These events can lead to acute danger (e.g., fatalities, injury, destruction of property). For example, the failure of two iron ore TSFs in Brazil in 2015 and 2019 resulted in numerous immediate fatalities (Vergilio et al., 2020). Although the acute effects of tailings dam failures are well documented, there is significantly less informa- tion in the scientific literature regarding the potential chronic environmental impacts on ecosystems and human populations. The most significant chronic environmental impact of tailings dam failures from gold mines is the release of metals, which can be dissolved in surface water runoff, sorbed to sediment particles, or dispersed by wind (Barcelos et al., 2020; Fashola et al., 2016). Metals can be a serious health issue because they persist in the environment and thus can pose long-term effects on ecosystems (Singh et al., 2011). Metal-rich sediments can be lethal to stream invertebrates and vertebrates at each level of the food chain (Vergilio et al., 2020), and metals that are deposited in soils adjacent to rivers can become incorporated into plants and crops, which can lead to negative
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 105 FIGURE 4-2â Modeled nitrogen loads from Virginia to the Chesapeake Bay (1985â2021) relative to the 2025 target. The loads are simulated using the Chesapeake Assessment and Scenario Tool version 2019 and jurisdiction-reported data on wastewater discharges. SOURCE: Data from Chesapeake Bay Program (2022). health effects if those plants or crops are consumed by humans (Barcelos et al., 2020). A key factor that influ- ences the magnitude of impacts from tailings dam failures is the bioavailability of the toxic metals in the tailings. The minerals that toxic metals are included within or sorbed to affect their availability to humans and wildlife (Barcelos et al., 2020). One case study relevant to Virginia is the Valzinco massive sulfide deposit in Spotsylvania County, which was mined intermittently until 1945. At the time of its reclamation in 2001, tailings had moved up to 2.5 km downstream of the failed tailings dam, contaminating the water with toxic metals (Hammarstrom et al., 2006; see Table 2-4). Another relevant case study is the tailings dam failure at the Mount Polley copper and gold mine in British Columbia, Canada. Analytical studies concluded that metals in the fine sediments deposited from the tailings breach were bioavailable and potentially toxic to invertebrates several years after the event (Pyle et al., 2022; see Box 4-2). WATER TABLE DEPRESSION The practice of dewatering a mine by pumping the water from the bottom of the pit or underground workings can affect the groundwater table (see Chapter 3). Groundwater wells near open pit or underground mines may run dry depending on the well depths, distance from the mine being dewatered, and the hydrogeologic properties of the local aquifers (see Figure 4-3). Mine dewatering in a low-permeability aquifer could create steep cones of depression in the water table that would affect residents living relatively close to the mine site. Dewatering in high-permeability or highly fractured aquifers, by contrast, could result in more extensive, but less steeply depressed, areas of drawdown that could be unequally distributed based on the orientation of bedrock fractures. The Piedmont and Blue Ridge regions of Virginia are composed of crystalline rock aquifers (86 percent), Early Mesozoic basins aquifers (9 percent), and low-permeability carbonate rock aquifers (3 percent; see Figure 4-4).
106 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA BOX 4-2 Other Case Studies of the Chronic Environmental Impacts of Tailings Release Besides Pyle et al. (2022), which describes the bioavailability of metals following the tailings dam failure at the Mount Polley copper and gold mine, there are few case studies that report the chronic environmental effects of TSF failures at gold mines. Below, two studies are described that report the chronic ecological effects of TSF failures, but that are unrelated to gold mining. The first relates to a failure at a zinc/silver/lead/copper mine in Spain and the second relates to an iron ore mine in Brazil. The 1998 mine tailings spill of 4 million cubic meters of acidic water and 2 million cubic meters of mud containing metals at the AznalcÃ³llar zinc, silver, lead, and copper mine in southwest Spain resulted in widespread distribution of zinc, lead, arsenic, copper, antimony, cobalt, thallium, bismuth, cadmium, silver, mercury, and selenium (Grimalt et al., 1999), much of it upstream of DoÃ±ana National Park, a critical habitat for migratory birds and other wildlife. In follow-up studies, underlying soil was found to contain a number of metals in an accumulation zone up to 30 centimeters deep (Kraus and Wiegand, 2006). The committee was unable to locate any published studies that identified human health impacts from environmental exposures from the AznalcÃ³llar spill, but metals such as arsenic, lead, and cadmium were elevated in tissues of terrestrial wildlife several years later in the areas impacted by the spill (Fletcher et al., 2006). Two major tailings dam failures occurred in Brazil, one in 2015 and the other in 2019. The first, the FundÃ£o Dam at the Germano iron ore mine in Bento Rodrigues in Minas Gerais State, released more than 40 million cubic meters of tailings, contaminating over 668 kilometers of surface waters. The second, when Dam B1 failed at the CÃ³rrego do FeijÃ£o iron ore mine in Brumadinho in Minas Gerais State, released 12 million cubic meters. Both incidents resulted in numerous immediate fatalities and a wide distribution of metals in the surrounding environment. Toxicological tests from the Brumadinho Dam rupture demonstrated that the contaminated soil and sediments could affect different trophic levels, from algae to microcrustaceans and fish. They also demonstrated that metals were accumulated in the muscle tissue of fish following the event (Vergilio et al., 2020). FIGURE 4-3â Pumping at an open pit mine in high-permeability homogeneous aquifers leads some wells near the mine to run dry due to groundwater table drawdown. The darker blue dotted line represents the water table prior to being altered by mining.
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 107 FIGURE 4-4â Rock types associated with aquifers in Virginiaâs Piedmont and Blue Ridge regions. SOURCE: Image modified from Trapp and Horn (1997). Groundwater in the crystalline rock and low-permeability carbonate rock moves along steeply angled joints and faults. Because bedrock fractures often have preferred directions of orientation, groundwater will flow more read- ily along those orientations (see Figure 4-5), making it more difficult to anticipate the exact area and magnitude of the groundwater drawdown (Cohen et al., 2007). Following the termination of pumping, the water table will begin to recover. The rate of recovery depends on the recharge rate and aquifer permeability. Recharge rate is highly variable in Virginiaâs Piedmont and Blue Ridge regions (e.g., varying from 4 to 28 inches per year in Bedford County; Cohen et al., 2007) and is determined by precipitation, runoff, and thickness of the unconsolidated material overlying the bedrock. The unconsolidated material is thicker in the Piedmont region than in the Blue Ridge region, which leads to faster aquifer recharge in the Piedmont (Trapp and Horn, 1997). However, even a temporary lack of well water for household use and irrigation may require installation of new wells or the transport of water to properties near the mine. If a new well FIGURE 4-5â Cross-section of crystalline rock aquifer in Virginia. (A) Groundwater-saturated bedrock fractures often have a preferred orientation. (B) Contours of equal water-level decline after pumping shows that preferred orientation of the fractures may lead to greater water-level decline parallel to the preferred direction of fracturing. SOURCE: Images from Trapp and Horn (1997).
108 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA is not provided, depression of the water table may lead to increased cost of living and decreased property values and quality of life for residents. Rivers, lakes, and springs have a close relationship with groundwater. Dewatering a mine can reduce surface water flows if these surface waters intersect the cone of depression of the water table and if the near-surface satu- rated zones are well connected with the aquifer being dewatered (and not separated by a confining layer such as clay or shale). If mine-related water withdrawals are large and significantly impact the flow volume of the stream, downstream water users and the ecosystem could be affected. Major impacts to surface water are not expected given the relatively limited size of mines expected in Virginia, although site-specific analysis would be needed for any proposed mine to evaluate potential impacts. AIR EMISSIONS Various air pollutants can be generated from mining activities (see Chapter 3). Some of these agents are hazardous air pollutants known to cause cancer or other serious health impacts (e.g., mercury, certain species of volatile organic compounds [VOCs]), whereas others are common air pollutants called criteria air pollutants (e.g., particulate matter, carbon monoxide [CO], sulfur dioxide [SO2], nitrogen oxides [NOx], ozone [O3]). Mining activities do not result in direct emissions of ozone but it can be produced through photochemical reactions in the presence of ozone precursors emitted from mines (namely, VOCs, CO, NOx). Historically, the most important impacts for mining-associated air emissions have been occupational exposures to certain kinds of particles that cause a large set of occupational lung diseases. These are generally interstitial lung diseases, and include examples such as asbestosis, coal workersâ pneumoconiosis (black lung disease), and silico- sis. Inhalational exposure to dusts containing high concentrations of elements such as aluminum, antimony, iron, and barium, or minerals such as graphite, kaolin, mica, and talc, can also cause pneumoconiosis (NIOSH, 2022). However, these minerals and elements are not found in high enough concentrations in the Virginia gold deposits that they would be a concern for the nonoccupational communities in Virginia. There are federal regulations and best practices to limit workplace exposure to dust, but the occupational impacts are not addressed in this report. Fugitive dust may be emitted from mine sites from drilling, blasting, ore crushing, roasting, smelting, hauling and moving of materials, operation of machines and vehicles on unpaved roads, and storage and disposal of waste. The dust produced from many of these operations tends to contain relatively large particles that settle out of the air quickly and do not penetrate far into the respiratory system (Entwistle et al., 2019). But if not controlled, these dusts can be hazardous, especially if they contain high concentrations of potentially toxic elements, such as the metals described in the âMetals and Metalloidsâ section. In fact, studies in Chile have reported that residential proximity to large gold or copper open pit mining was associated with a higher prevalence of respiratory diseases among children (Herrera et al., 2016, 2018). However, fugitive dust can generally be limited through best practices on mine sites (see Chapter 3) and is typically less of a concern in the United States than in low- and middle-income countries where dust emissions are less regulated (Entwistle et al., 2019). Hence the spatial and temporal scales of the impacts of fugitive dust from gold mining in Virginia would be fairly limited. Nevertheless, when fugitive dust is not properly controlled on mine sites it can be a significant concern to nearby communities and can adversely affect public health. Another source of air pollutant from gold mines that may impact air quality and public health beyond the mine site is the exhaust from fuel-burning vehicles and machines. Combustion of fossil fuels, in particular diesel, leads to emissions of gases and vapors, including CO, NOx, and VOCs, as well as fine particulate matter that comprises elemental and organic carbon, ash, sulfate, and metals (IARC, 2014). Diesel exhaust is a Group 1 carcinogen that can cause lung cancer and bladder cancer (IARC, 2014). The impact of diesel exhaust will be proportional to the truck traffic and heavy equipment operation at the site. Given that future gold mining operations in Virginia are likely to be limited in size, the impacts of diesel emissions on surrounding communities may be limited. Other activities on a mine site may also produce air emissions. For example, the processing of ores, including the high-temperature combustion or heating processes such as roasting and smelting, can release nitrogen oxides, sulfur dioxide, and mercury. The amounts of mercury compounds produced are very site specific and dependent on the ore composition and the mining processes used. In 2018, the processing plant at Haile Gold Mine in South Carolina exceeded compliance levels for mercury (40 CFR Pt. 63 Subpart EEEEEEE, 2022). In response
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 109 to this, Haile operators installed a mercury abatement control device system and the mine has not exceeded mercury compliance levels since (USACE, 2022). The source of the mercury was unclear in this case (Morton, 2020). Although the committee does not have any evidence of elevated mercury in Virginia gold deposits, there are limited data, which leaves significant uncertainty. In addition, there could be significant amounts of mercury near old gold mine sites where mercury was once used during gold processing (see Chapter 2). If mercury from contaminated historical mine sites was inadvertently brought into the processing stream, it could lead to atmo- spheric emissions. Most atmospheric mercury is in the metallic gaseous form (about 90 percent or greater), but atmospheric redox reactions can convert mercury between different forms (Horowitz et al., 2017). Metallic mercury has a long atmospheric lifetime (around 1 year), enabling it to be transported far downwind (Horowitz et al., 2017) before redepositing to Earthâs surface. The redeposited mercury has further implications for soil and water quality. Effective control strategies and techniques have been developed for various mining-associated emissions. Examples include spraying water or dust suppressant on roads and waste piles, reducing open surfaces, enclosing ore-crushing areas, switching from internal combustion engines to other power sources, and applying air pollu- tion control systems (scrubbers) for specific air pollutants. There are very effective (with 90 percent or greater controlling efficiency) air pollution control systems for all the major air pollutants, including particulate matter, sulfur dioxide, nitrogen oxides, VOCs, and mercury. Such systems are widely used in stationary sources such as power plants, oil refineries, and manufacturing settings and similar approaches have been used in gold mining operations at Haile Gold Mine in South Carolina (USACE, 2022). The impacts on air quality from various sources of air pollution depend not only on the emission fluxes but also on the background or baseline air quality (Sillman et al., 1990; Wu et al., 2009). The committee reviewed air quality data from Virginia for the past 5 years (EPA, 2021a). All the criteria air pollutants were found to be in compliance (levels lower than the National Ambient Air Quality Standards [NAAQS]) for gold-bearing regions in Virginia, but there were multiple counties with fine-particle particulate matter (PM2.5) levels close to the NAAQS (annual average of 12 Î¼g/m3 and 24-hour average of 35 Î¼g/m3). CUMULATIVE HEALTH IMPACTS FROM COMBINED EXPOSURES Recently, there has been growing recognition that human populations and ecosystems are exposed to multiple stressors in combinations that can interact in a dynamic way to produce a range of outcomes. In 2003, EPA developed a long-term initiative to evaluate combined risks of adverse effects on human health or ecosystems from multiple environmental stressors (Callahan and Sexton, 2007). Stressors that may impact human or ecological health include not just chemical toxicants but any combination of chemical, biological, physical, and psychosocial hazards. Impor- tantly, special attention has been given to evaluating how chemical and nonchemical stressors can interact to increase the risk of adverse health outcomes (Sexton, 2012). Progress on EPAâs cumulative risk assessment efforts has been somewhat slow because studies of concurrent exposure to multiple hazards are more methodologically challeng- ing, time-consuming, and costly to conduct. For cumulative ecologic risk assessment, the additional complexities are often so significant that many of the available studies are only qualitative or semiquantitative (EPA, 1998a). Several kinds of complexity are introduced by the cumulative risk assessment process. These include time- and spatial-related aspects of exposures (e.g., concurrent exposure, serial exposure, past exposure in critical time period combined with current exposure), vulnerability of exposed populations (i.e., based on biology, exposures, underlying health, and recovery), identification of subgroups with exposures of special concern (e.g., higher exposures based on occupation or behaviors), and characterization of interactions between psychosocial stress (i.e., that could arise from poverty, inadequate housing, street crime, discrimination, unemployment, and other sources of stress) and other hazardous exposures (Callahan and Sexton, 2007; EPA, 2003; Gallagher et al., 2015). When populations are exposed to more than one hazard at a time, effects can exhibit a range of risks that may equate to a sum of the individual risks or exceed that sum. Studies of multiple hazards are increasingly appearing in the peer-reviewed scientific literature and highlight that concurrent exposure to multiple pollutants and exposure to chemical and nonchemical stressors can increase the risk of adverse health outcomes (Bobb et al., 2015; Domingo-Relloso et al., 2019; Green et al., 2015; Iakovides et al., 2021; Lee et al., 2021; Meza-Montenegro et al., 2012; Park et al., 2017; Peters et al., 2014; Sanders et al., 2019; Wang et al., 2018, 2020a,b, 2021; Xiao et al., 2021b; Zhou et al., 2019). Studies like
110 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA these have direct relevance to gold mining in Virginia because they suggest that the toxicant exposures arising from gold mining operations could differentially impact the health of populations that experience concurrent exposure to nonchemical stressors that affect psychological or physical health. Gold mining operations present multiple hazards to communities, including direct exposure to pollutants, increased stress, and changing perceptions of community conditions. These different hazards can interact to increase the risk of adverse health outcomes. For example, a study in a community with small-scale and industrial-scale gold mining in Ghana evaluated perceived stress, salivary cortisol as a biomarker of stress, personal noise exposure, and heart rate, documenting that communities with gold mining can experience multiple, often additive, exposures that can contribute to such health outcomes as hearing loss and cardiovascular disease (Green et al., 2015). In addi- tion, these mixed exposures are occurring in populations with differences in social vulnerability (Emmett, 2021), underlying health vulnerability, behavioral vulnerabilities, and individual susceptibility to these factors. Because of this, the impacts of degraded water quality from mining on nearby populations are best interpreted in light of a variety of cultural, social, and economic vulnerabilities (French et al., 2017). The County Health Rankings system is one tool for considering the concurrent stressors that may already exist in Virginian communities (see Figure 4-6). This tool evaluates health outcomes according to premature FIGURE 4-6â Health outcome and factor rankings for all counties in Virginia with higher rankings (darker shading) being worse for health outcomes and factors. Black outlined areas are the gold pyrite belt and the Virgilina district, and the yellow dot is the recent exploratory drilling in Buckingham County. (A) Health outcomes include premature death, poor or fair health, poor physical health days, poor mental health days, and low birthweight. (B) Health factors include access to clinical care, local economics, and prevalence of behaviors that can affect health. Some of the southern regions of the gold-pyrite belt and the Virgilina district have worse health outcomes and health factors than the northern part of the belt. For example, Buckingham County was ranked in the second worst quartile for health outcomes and the lowest quartile for health factors. SOURCE: Modified map from The University of Wisconsin Population Health Institute (2022).
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 111 death, poor or fair health, poor physical health days, poor mental health days, and low birthweight. It also evalu- ates health factors using nine indicators for health behaviors (e.g., adult smoking, physical inactivity, teen births), seven indicators for clinical care (e.g., uninsured, mental health providers, flu vaccinations), nine indicators for social and economic factors (e.g., high school completion, children in poverty, income inequality, violent crime, injury deaths), and five indicators for physical environment (e.g., particulate matter air pollution, drinking water violations, severe housing problems). The impacts of mining also tend to be distributed unevenly across landscapes and communities, based on proximity to the mine site, characteristics of the physical environment, socioeconomic and political structure, and demographic factors. Some communities are relatively successful in exercising self-determination with regard to proposed mineral mining projects, for example by ensuring that mineral developments reflect community priorities. Other communities with less socioeconomic or political influence, especially those who live near the mine, tend to bear the brunt of the negative impacts of mining, but the positive impacts accrue to others, including investors, shareholders, and users of the end products manufactured from mined materials (Dunbar et al., 2020). This poses well-established environmental justice issues (Kivinen et al., 2020). As defined by EPA, environmental justice ensures that all communities have the same degree of environmental protections and equal access to the decision- making processes that shape the environments in which they live (EPA, 1994a). Environmental justice is at the intersection of environmentalism (protect and improve the environment) and justice (fairness among members of society) and fundamentally addresses the fact that the health impacts of environmental degradation are unevenly distributed across society. Hence, environmental justice efforts address such issues as the disproportionally high distribution of industrial activities in poor and minority communities, the heightened impacts of pollution in these communities, the lower prevalence of environmental amenities in such communities (e.g., green spaces, healthy food), and the complicating factor that such places also are characterized by worse access to health care, worse underlying health, and higher prevalence of adverse health behaviors that make these populations more vulner- able to the hazardous agents (Diez Roux and Mair, 2010; Hilmers et al., 2012; Hynes and Lopez, 2007; Olvera Alvarez et al., 2018). Mining operations have long been a focus of environmental justice concerns (Aydin et al., 2017; Lewis et al., 2017; LiÃ©vanos et al., 2018; Morrice and Colagiuri, 2013). For example, the impacts of acid rock drainage are different in Indigenous communities than in non-Indigenous communities (Clausen et al., 2015). CONCLUSIONS AND RECOMMENDATION This chapter outlines the potential human health and ecological impacts from gold mining in Virginia based on a review of the impacts of gold mining at U.S. and international sites and on the concerns expressed by com- munity members during the information-gathering activities for this study. As little commercial gold mining has occurred in Virginia in the past 70 years, there is limited information about the impacts from historical gold mining in Virginia or the constituents of concern in the remaining gold deposits. The committee therefore could not predict site-specific impacts from gold mining in Virginia, but instead evaluated the impacts reported at other gold mining sites in the context of the environmental, geologic, and social conditions of the gold-bearing regions of the Commonwealth. The committee used the best available scientific and technical information to draw the following conclusions and recommendation. Remobilization of Legacy Contaminants Remobilization of legacy mercury from mining operations that take place at historically mined sites poses a significant risk to human health and the environment. Mercury is no longer used for the processing of gold in the United States, but it was used at historical gold mines in Virginia. As a result, considerable legacy mercury may exist in surface waters, soil, and mine waste at previously mined sites. These areas may still harbor unmined gold deposits and unrecovered gold in historic waste material, and future gold mining operations could remobilize this legacy mercury unless appropriate extraction and processing circuits are implemented to capture the mercury. Because of mercuryâs high toxicity, careful characterization for mercury is essential at all potential mine sites in order to protect environmental and human health.
112 THE POTENTIAL IMPACTS OF GOLD MINING IN VIRGINIA Impacts to Water Quality Acid rock drainage (ARD) is among the most important potential environmental impacts of concern and poses a substantial risk if massive sulfides are disturbed during gold mining operations and if proper engineering controls are not in place. ARD can persist long after mining has ended and can cause acidity, high salinity, and elevated concentrations of toxic metals in surface water and groundwater if appropriate engineer- ing controls are not in place. Many gold deposits in Virginia are not directly associated with large quantities of sulfide-containing minerals, reducing the likelihood of extensive ARD associated with mining. However, if adjacent massive sulfide deposits or sulfide-bearing country rock are disturbed and if appropriate engineering controls are not applied, ARD could adversely impact sensitive freshwater fauna in nearby streams and wetlands, resulting in substantial remediation costs. Site-specific characterization, engineering controls, and monitoring throughout the life cycle of gold mines are important to minimize and mitigate ARD that could negatively impact surface water and ecological communities. Site-specific geologic conditions determine whether metals could be released from gold mining opera- tions in sufficient quantities to pose human health threats to surrounding communities. The primary elements of concern for human health that could be released from Virginia gold deposits or from nearby rocks disturbed during mining include antimony, arsenic, cadmium, lead, mercury, and thallium. Most Virginia gold deposits occur in low-sulfide, gold-quartz veins and the few reliable geochemical data that are available for these deposits show low concentrations of metals of concern in discharge waters. However, some gold deposits in Virginia are located in close proximity to massive sulfide deposits, which have higher concentrations of pyrite and higher risk of toxic metal discharge, leaving considerable uncertainty in predicting risk across the state. Therefore, any future efforts to mine gold deposits in Virginia should be accompanied by detailed studies to characterize the mineralogy, metal content, and geochemistry of each deposit and its surrounding rock. Site-specific characterization, water quality management, and monitoring throughout the life cycle of gold mines will be important to minimize and mitigate the release of metals that could negatively impact surface water and groundwater quality. Mining can increase nitrate loading to local waterways, which can contribute to eutrophication of local surface waters. Although best practices for blasting activities can limit nitrogen loading of surface water and groundwater (see Chapter 3), incomplete combustion of ammonium nitrate and fuel oil explosives under wet, nonideal conditions may result in nitrate-laden mine-influenced water that can exceed water quality criteria. If this water is not appropriately managed and it reaches local surface waters without significant dilution, depleted dissolved oxygen and reduced pH due to eutrophication may result, which can be lethal to invertebrates and fish. Mining could also contribute to the total loading of nitrogen to more distant habitats (e.g., the Chesapeake Bay), although the relative contributions to the total loads are expected to be small. Elevated nitrate in drinking water can also be harmful to human populations, but these higher concentrations are likely only possible in groundwater in the immediate vicinity of the mine site and can be prevented with best practices for blasting activities. Open impoundments that contain cyanide pose acute toxicity risks to wildlife unless proper management and deterrents are in place. Wildlife species are attracted to virtually any kind of surface water body, natural or constructed, including waste and treatment impoundments. In the arid western United States, there have been numerous acute toxicity events affecting wildlife (especially birds) at cyanide impoundments in gold mining sites, although there have been fewer reports documenting these toxicity events following the establishment of modern best practices for cyanide management. Although surface water is plentiful in Virginia, the Commonwealth hosts diverse and abundant wildlife species that are dependent on access to open surface water. Unless best practices (e.g., deterrent systems, cyanide destruct systems) or alternative methods (e.g., enclosed tank leaching) are used, wildlife acute toxicity events could occur at open impoundments containing cyanide. Impacts to Air Quality The committee did not find evidence to indicate that gold mining in Virginia would significantly degrade air quality if appropriate engineering controls were in place. Fugitive dust produced from excavation activities, heavy equipment, and mine road traffic can be a nuisance that impacts the quality of life of affected neighbors. In addition, toxic fine particles and gaseous pollutants generated from fuel combustion and gold processing can
POTENTIAL IMPACTS TO HEALTH AND THE ENVIRONMENT 113 be hazardous if released, because of their greater respiratory impacts and longer atmospheric transport distance. Given the likely small scale of future commercial gold mining in Virginia that would lead to limited heavy equip- ment operation and traffic, and the technological advancements in recent decades that allow for effective dust suppression and control of hazardous air pollutants, the impacts of air pollutants on surrounding communities are expected to be limited. Rare But Catastrophic Events Catastrophic failures of gold mine tailings dams and cyanide solution containment structures are low- likelihood but high-consequence events that have caused significant impacts where they have occurred. Tailings dam failures can lead to acute danger (e.g., fatalities, injury, destruction of property) as well as long-term ecological effects that are caused by the dispersal of toxic metal-containing mine wastes in rivers and floodplains. The magnitude of the long-term ecological effects depends on the scale of the spill, bioavailability of the contami- nants, and effectiveness of cleanup efforts. In contrast, cyanide spill events do not pose long-term risks because cyanide degrades in the surface environment relatively quickly. However, because of cyanideâs high acute toxicity, accidental spills have caused mass mortality events of aquatic life and pose an acute human health risk where water affected by the spill is used as a drinking water supply. If tailings and cyanide containment structures are not designed to accommodate seismic, high-precipitation, and flooding events, then the likelihood of these potential high-consequence events will increase. This is especially pertinent in light of the potential for increased frequency and severity of precipitation events due to climate change. Impacts to Water Quantity Drawdown of the water table associated with the dewatering of an open pit or underground mine could impact local groundwater users, depending on aquifer conditions and the proximity of wells to the mine site. Unless drawdown effects are appropriately mitigated, these impacts could significantly affect the quality of life and the cost of living for residents near the mine site who rely on groundwater supplies. Rigorous site character- ization and modeling is needed to estimate the level and geographic span of groundwater impacts and to evaluate whether alternative sources of water or new wells need to be provided to local citizens. Public engagement and participation during permitting is essential if alternative sources of water or new wells may need to be provided. Cumulative Risk Robust analyses of the potential impacts of mining consider cumulative health risks. Human populations are exposed to multiple hazard types, including biological, physical, chemical, psychological, and social (e.g., poverty, discrimination, unemployment, limited access to health care). These hazards can occur through different exposure settings (e.g., environmental, occupational) and multiple media (e.g., air, water, soil). Different hazard types, especially chemical and nonchemical stressors, can interact to affect human health in complex and dynamic ways. These multiple, sometimes synergistic, stressors can lead to asymmetric impacts within and between com- munities, and historically underresourced and underrepresented populations are often most affected. *** In light of the general impacts of gold mining in Virginia that are outlined in the conclusions above, robust site- and project-specific analyses are necessary in order to assess potential impacts and determine what mining operation procedures will be most protective of human and ecological health. RECOMMENDATION: To minimize impacts to human health and the environment, the Virginia Gen- eral Assembly and state agencies should ensure that robust site- and project-specific analyses of impacts are completed prior to the permitting of a gold mining project.