Review of Fate, Exposure, and Effects of Sunscreens in Aquatic Environments and Implications for Sunscreen Usage and Human Health (2022) / Chapter Skim
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3 Problem Formulation: Sources, Settings, and Ecological Receptors
3 Problem Formulation: Sources, Settings, and Ecological Receptors
Pages 37-68
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From page 37... ...
filters, specifically discussing point and nonpoint sources of UV filters reaching aquatic ecosystems and, to a lesser extent, terrestrial systems. After describing sources of UV filters reaching ecosystems, this chapter outlines conceptual models for potential UV filter exposure in different environmental settings and how these are used to frame the state of knowledge for multiple aquatic environments (to be elaborated upon in subsequent chapters)
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From page 38... ...
While it would likely be difficult to confirm that observed UV filters originated from sunscreens specifically, the exposure routes explored here are those most likely to be relevant to sunscreens. Direct Release of UV Filters During Recreational and Other Direct Surface Water Contact Activities Release of UV filters from bathers and other aquatic recreational activities (e.g., swimming, surfing, diving, boating)
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From page 39... ...
Prior to these recent developments of a standard approach for estimating rinse-off rates, and in the absence of detailed information for all of the formulations of currently marketed sunscreens, researchers have assumed that some fraction of applied sunscreen rinses off during aquatic recreational activities. A number of studies have assumed a fraction, from 20 to 100 percent, of applied sunscreens rinse off directly into surface water (see Sharifan et al., 2016)
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From page 40... ...
Diurnal patterns in UV filter concentrations in surface waters provide additional evidence of the direct inputs of sunscreen from recreational bathing (Tovar-Sánchez et al., 2013)
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From page 41... ...
The authors also noted that pool-system filtration systems may have removed some of the particulate TiO2. Thus, unless such water treatment technology is specifically considered, this may influence the utility of swimming pool studies as a means to estimate UV filter input rates in outdoor aquatic environments.
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From page 42... ...
While most treated wastewater is discharged to surface waters, in some regional cases treated wastewater is infiltrated or injected into groundwater, used in industrial cooling facilities, evaporated from lined ponds, or applied to agricultural crops. In addition to the liquid effluent discharge, sewage solids (biosolids)
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From page 43... ...
Activated sludge Mid- to large-sized community (>10K River, lake, estuary, offshore ocean pipeline people) Package biological and membrane Cruise ships, hotels Offshore, open ocean, and occasionally harbors filtration system a Each system type will also produce bacterial sewage solids of some form; these are continuously produced and are disposed of daily, monthly, or annually depending upon size and type of facility.
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From page 44... ...
FIGURE 3.3 Schematic of a fully enclosed septic tank and perforated pipes that distribute water from the septic tank into a leaching field. SOURCE: EPA, https://www.epa.gov/septic/types-septic-systems, retrieved February 2022.
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From page 45... ...
values for septic systems (n = 8) , leaching fields (n = 1)
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From page 46... ...
While few studies have measured occurrence, removal, and release of organic UV filters themselves through septic systems, there is compelling evidence that other PPCPs occur in septic systems at concentrations much above those at municipal wastewater treatment plants. In the absence of other information, PPCPs are used here as surrogates or "markers" for potential treatment and off-site migration of UV filter chemicals from on-site systems.
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From page 47... ...
. In other work, minimal effects of ZnO were reported, and laboratory studies to simulate wastewater treatment observed about 70 percent removal of ZnO during sedimentation and near complete removal from the effluent during simulated biological treatment (aeration + sedimentation cycles)
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From page 48... ...
However, there is a significant data gap in measurement of concentrations, removal efficiencies, and off-site groundwater migration assessments for the broad range of organic UV filter chemicals. Poorly maintained on-site treatment systems can increase the release of UV-filters into groundwater, and subsequently impact nearby surface waters.
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From page 49... ...
TABLE 3.3 Predicted Removal of Nondeprotonated Forms of Organic UV Filter from Wastewater Treatment Contribution Toward Total Removal by Three Different Mechanisms Total Removal Biodegradation Removal Sludge Adsorption Removal Organic UV Filter (%)
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From page 50... ...
Freeze-dried sewage solids underpredicted the potential removal of TiO2 and other inorganic colloids/nanomaterials (Kiser et al., 2012; OECD, 2021)
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From page 51... ...
when undergoing primary treatment and > 55 percent of compounds experienced high removal with secondary treatment; reverse osmosis resulted in the highest removal efficiencies (Tsui et al., 2014a)
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From page 52... ...
3. Ready biodegradable: An arbitrary classification of chemicals which have passed certain specified screening tests for ultimate biodegradability; these tests are so stringent that it is assumed that such compounds will rapidly and completely biodegrade in aquatic environments under aerobic conditions.
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From page 53... ...
Thus, it is sometimes also of interest to study the combined effect of degradation and sorption on wastewater treatment plant removal as well as degradation in other environmental systems such as surface water, sediment, soil, and marine waters. Importantly, however, biodegradability test data may lack realism compared to real-world situations due to extremely high dose rates used (i.e., orders of magnitude above limits of solubility)
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From page 54... ...
) conditions is an endpoint with low capacity for detection; studies in WWTP above solubility reduces applicability ISO 11734 Aerobic WWTP Headspace CO2 Nonbiodegra- Exposure above seeded with AS = 0% dable solubility limit OECD Guideline 308 Sediment Half-life in Inherently Radiolabel study I sediment = 124 d biodegradable OECD Guideline Surface water Half-life in Inherently Radiolabel, several I – metabolite 309 (Aerobic surface water = biodegradable metabolites detected formation Mineralisation in Surface 11.2-11.9 d Water - Simulation Biodegradation Test)
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From page 55... ...
OECD Guideline 301 Inorganic carbon Nonbiodegra (Ready Biodegradability removal = 0.9% dable - CO2 in Sealed Vessels (Headspace Test) Ensulizole OECD Guideline 301 F Aerobic WWTP O2 consumption Nonbiodegra- Exposure above N aerobic (Ready Biodegradability: seeded with = 0% dable solubility limit Manometric Respirometry Mixed Inoculum N anaerobic Test)
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From page 56... ...
OECD Guideline 301 F Aerobic WWTP O2 consumption Ready Exposure above (Ready Biodegradability: seeded with AS = 70% biodegradable solubility limit Manometric Respirometry from lab WWTP Test) Octisalate EU Method C.4-E Aerobic WWTP O2 consumption Ready Studies in WWTP R aerobic (Determination of the seeded with AS = 89% biodegradable above solubility "Ready" Biodegradability reduces applicability - Closed Bottle Test)
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From page 57... ...
Mixed Inoculum solubility reduces Preparation: applicability Polyseed OECD Guideline 301 F Aerobic WWTP DOC removal = Nonbiodegradable Non-GLP (Ready Biodegradability: seeded with 0–10% Manometric Respirometry effluent from lab Test) WWTP OECD Guideline 302 B Aerobic WWTP DOC removal = Ready Zahn-Wallens (Inherent biodegradability: seeded with AS 71% biodegradable includes removal Zahn-Wellens/EMPA from lab WWTP by sorption and Test)
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From page 58... ...
Results are then interpreted as robust conclusions regarding biodegradability under conditions of municipal wastewater treatment plant removal. R = ready; I = inherent; U = ultimate; N = nonbiodegradable.
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From page 59... ...
will depend on the mass of the UV filters being used and their propensity for either washing off skin at bathing beaches, passing through publicly owned treatment works, or reaching surface waters via leaching into soils (especially if sewage solids are applied) and subsequent groundwater transport or direct land runoff (after wind and storm events)
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From page 60... ...
Other more diffuse sources include septic systems near water bodies, and nonpoint sources including urban and agricultural runoff. The magnitudes of sunscreen-associated UV filters entering the aquatic environment depend in large part on the number of people engaged in recreational activities or population sizes being serviced by WWTPs.
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From page 61... ...
This means that embayments or water bodies that are relatively quiescent, with shallow or low water volumes, or have longer residence times, are more prone to exposures of receptors than are aquatic environments characterized by higher energy physical processes (e.g., high flushing and/or advection rates)
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From page 62... ...
Water bodies hydraulic connectivity with minimal water exchange Urban Rinse stormwater Landfill off discharges Leachate station Septic tank and cesspool releases Aquifer Recreational release Surface/groundwater hydraulic connectivity Minimal mixing with external waters (c) Waterways with rapid water Leach ponds Manufacturing Landfill movement Leachate Urban Agricultural stormwater runoff and combined sewer overflow discharges Septic tank and Wastewater cesspool discharge releases Sludge Groundwater Biosolid Recreational recharge application release Aquifer Rapid Surface/groundwater water hydraulic movement connectivity FIGURE 3.9 Three representative conceptual frameworks for sources of sunscreens into the environment.
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From page 63... ...
along with the conceptual scenarios illustrated in Figure 3.9 provide a framework for considering how exposures might vary and how information on exposure from one type of location could be used to inform an assessment of exposures in another system. For example, a near-shore, semi-enclosed, shallow fringing reef system such as Hanauma Bay, Oahu, Hawaii, would be expected to have a larger source magnitude, experience longer residence times, and be nearer to the source than the offshore, open, deep barrier reef system bordering the Florida Keys, Florida (Figure 3.10)
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From page 64... ...
Many conceptual models can be constructed to convey exposure pathways for ecological receptors in the diverse aquatic and marine systems illustrated in Figure 3.9. One example is given for a coastal aquatic system with an upstream freshwater component (Figure 3.12)
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From page 65... ...
Upon entering aquatic environments, UV filters will partition into various environmental media including air, water, suspended solids, surface microlayers, and sediments. The dissolved phase of a UV filter in water is an important route for direct exposure to membranes such as those used for respiration and nutrition (e.g., gills and other surfaces that permit exchanges of dissolved gasses, nutrients, and other chemicals between the animal and the environment)
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From page 66... ...
However, exposures of aquatic ecological receptors to UV filters depend on a combination of factors pertaining to the physico-chemical properties of the chemical and its interaction with, and ultimate fate in, environmental settings. UV filters vary in their aqueous solubility, lipophilicity, and degradation rates.
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From page 67... ...
Finding: Through engineered processes at most wastewater treatment facilities, homosalate, meradimate, octocrylene, octinoxate, octisalate, and padimate O, as well as the inorganic UV filters titanium dioxide and zinc oxide, are most likely to be highly removed from the effluent. Studies have shown their presence in sewage solids that are collected and disposed of off-site (landfills, land applied, incinerated)
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