Global Issues in Water, Sanitation, and Health Workshop Summary (2009) / Chapter Skim
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3 Vulnerable Infrastructure and Waterborne Disease Risk
3 Vulnerable Infrastructure and Waterborne Disease Risk
Pages 153-199
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From page 153... ...
and identify emerging needs in waterborne disease prevention and control, which include a deeper understanding of the ecology of waterborne disease as it pertains to drinking water distribution systems, safe water reuse programs, and an estimate of the burden of waterborne disease in toto to advocate for, as well as inform, active surveillance efforts. Climate change presents a serious challenge to safe water availability worldwide, for numerous reasons summarized by presenter Joan Rose of Michigan State University in the chapter's second paper.
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From page 154... ...
Following a description of microbial risk assessment methodologies for waterborne disease, the authors review representative studies (most of which were conducted in the United States) that describe drinking water contamination and the role of the water distribution system in spreading waterborne disease, as well as that played by premise plumbing and the biofilms present therein.
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; • Link test development to waterborne disease epidemiology and quantita tive risk assessment; and • Use test as a tool for education and policy making.
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Hlavsa, R.N., M.P.H.2 Centers for Disease Control and Prevention The timing for this presentation is fortuitous since it is September 23, 2008, the eve of the 100th anniversary of the addition of chlorine to the Jersey City, New Jersey drinking water supply -- the first time chlorine was added to water to kill microbes and improve water quality at an American drinking water treatment plant. This centennial reminds us, as we explore current challenges in providing safe drinking water in this country, of the pivotal role that inclusion of filtration and disinfection in water treatment plants had in reducing the burden of waterborne diseases in the United States (Cutler and Miller, 2005)
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From page 157... ...
Annual or biennial surveillance summaries of the data have been published by CDC since the system's inception in 1971. This system is now the primary source of data on waterborne disease outbreaks (including those caused by pathogens, chemicals, and toxins) associated with ingestion, contact, or inhalation of drinking water, recreational water, or water not intended for drinking (i.e., cooling towers, industrial use)
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. The Surface Water Treatment Rule of 1989 was designed to prevent waterborne diseases caused by viruses, Legionella, and Giardia intestinalis.
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May be single or multiple deficiencies associated with each outbreak. SWTR = Surface Water Treatment Rule.
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, will eventually produce a decline in groundwater-related disease outbreaks similar to the results observed after enactment of the Surface Water Treatment Rule. • Individual or unregulated water systems represent an important gap in waterborne disease prevention.
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. As Figure 3-4 demonstrates, an increasing proportion of reported waterborne disease outbreaks are associated with use of individual private wells.
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Limitations of Waterborne Disease Surveillance While the WBDOSS has been useful in elucidating the aforementioned trends and, therefore, highlighting areas of emerging public health need, this surveillance system has a number of critical limitations. First and foremost, the WBDOSS is a passive system based on outbreak reports from state and local public health agencies that do not necessarily actively track waterborne disease outbreaks.
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. However, these estimates need to be refined as better data and improved methods of estimating endemic waterborne disease become available.
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report, Drinking Water Distribution Systems: Assessing and Reducing Risks, the water distribution system is the one remaining component of U.S. public water systems yet to be adequately addressed to reduce waterborne disease outbreaks; thus, the committee recommended conducting epidemiological studies that specifically target the distribution system component of waterborne diseases (NRC, 2006)
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, and the potential impact of severe weather on waterborne disease is part of a larger discussion about potential climate change impacts on public health (Patz et al., 2000, 2008; Rose et al., 2001)
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While the incidence of the drinking water–associated disease outbreaks has decreased over the last several decades (Yoder et al., 2008b) , WBDOSS reporting has demonstrated a dramatic increase in the number of AGI outbreaks attributable to recreational water use in the United States (Figure 3-6)
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To our detriment, those of us who study waterborne disease tend to compartmentalize water. We attend drinking water meetings, recreational water meetings, water conservation meetings, and so on, but we too often fail to look at water 10 All regulation of public pools in the United States is set at the state or local level.
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In order to address the threat of waterborne disease over the long term, it will be essential to assess all types of water use, study the impact of both microbial and chemical contamination, and investigate the sources of human- and animalspecific contamination. This will require multiyear intervention studies, laboratory methods development, and health-effects studies, involving state, local, and federal agencies, as well as academic researchers in the United States.
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From page 169... ...
These include drought, decreased water availability and deteriorating water quality, aging water infrastructure, climate change impacts, chemical contamination, and the potential emergence of newly identified waterborne disease pathogens, which may be more difficult to combat because of chlorine or drug resistance. Preparing our public health system to address these challenges, as would occur if the proposed "WaterNet" platform were implemented, would provide essential information needed to prevent waterborne disease and strengthen public health protection of U.S.
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From page 170... ...
Our ability to understand the effects of climate fluxes on the changes in water quality, which may in turn affect the likelihood of waterborne diseases, moves the field closer toward building predictive approaches that can be used for science and evidence-based management strategies. The research on water quality-health-climate interactions has focused on three main lines of evidence:
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From page 171... ...
Human Disease and Climate: Waterborne Diseases Some of the strongest evidence now emerging is the association of precipitation as an extreme event with drinking waterborne disease outbreaks in the United States and Canada. About 50 percent of the outbreaks in the United States were statistically associated with extreme rainfall (at the 95 percentile compared to the 25-year average)
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From page 172... ...
To a large extent, the Australian army and other groups are to be credited with rapidly deploying environmental health teams to swiftly implement public health measures, including provision of safe drinking water, proper sanitary facilities, and mosquito control measures. Widespread fecal pollution of the surface waters was shown, yet the saltiness of the potable water supply after the disaster made much of the water unpalatable.
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. Water Quality Changes in Fecal Pollution Indicators and Pathogens Associated with Climate In order to build an understanding of the public health risks associated with climate, the development of models of water quality changes are needed.
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While this seems obvious many scientific investigations fail to address the variability in pathogen types and concentrations in relationship to the sources, the climate event, and the disease outcomes. For example, studies after Hurricane Floyd showed significant water quality impacts via fecal indicators and in areas with high concentrations of pig farms that illnesses associated with specific etiological agents such as Adenovirus, Cryptosporidium, Giardia, Toxoplasma, and Helicobacter were not increased after the flooding even though unidentified illnesses did increase (from 5.1 to 11 outpatient visits per month)
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Here, I would suggest that sewage and human fecal pollution is the source; that climate is the driver of exposure; and, thus, one might hypothesize that the wastewater and drinking water infrastructure, the types of pathogens at any given time in the community wastewater, and the characteristics of the flooding would drive the risk of disease. In order to examine the parameters associated with the risk of disease transmission, a Quantitative Microbial Risk Assessment (QMRA)
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percentiles of risk displayed. Bar graph demonstrates the uncertainty analysis associated with sewage concentrations of the pathogens (red bar)
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Some of the critical needs that must be met in order to predict the effect of climate change on waterborne disease are • better knowledge of disease incidence and pathogen excretion; • better assessment of concentrations of pathogens in sewage and other sources; • better assessment of the vulnerability of pathogen sources (e.g., combined sewer overflows versus septic tanks) ; • better monitoring of sewage indicators to gather source, transport, and exposure information (event monitoring)
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Thus, as we move vector, editable forward in investing our own water infrastructure in the United States and develop redrawn serious programs to work at the global level, we should also invest in gathering the information and knowledge that will allow us to make informed decisions to assist in adaptation and mitigation strategies. Quantitative Microbial Risk Assessment of Waterborne Disease Kelly A
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The need to standardize the risk assessment approach in making quantitative assumptions, while minimizing uncertainties, is apparent across multiple disciplines. TABLE 3-1 National Research Council Risk Assessment Paradigm Hazard identification Identification of hazards, incident scenarios, potential consequences, and agent properties, including factors of virulence, adaptation, resistance, and mutation.
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However, inadequate, interrupted, or intermittent treatment has repeatedly been associated with waterborne disease outbreaks. Drinking water outbreaks exemplify known breaches in municipal water treatment and distribution processes and the failure of regulatory requirements to ensure that water is free of human pathogens.
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and by 2014 for CWSs with outstanding performance and for all non-CWSs to help identify deficiencies that may lead to impaired water quality. Source water monitoring for indicator microbes, corrective actions for systems with significant deficiencies or source water fecal contamination, and compliance monitoring are further required.
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of water distribution has been associated with worldwide epidemics (reviewed in Lee and Schwab, 2005)
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. Epidemiological Research The true burden of waterborne disease is unknown in the United States, although variable approaches have been used to estimate gastrointestinal illness from waterborne pathogens, including epidemiological studies and exposure analysis.
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A follow-up study attempted to evaluate the role of distribution system water quality in gastrointestinal incidence and involved four groups of participants: a tap water group and a bottled purified water group (to address those exposed and unexposed, respectively) , and a plant bottled water group and a tap water group using a purge valve (to address distribution system water quality)
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Contamination is not evenly distributed but rather is affected by differences in source water quality, hydraulic flow, mixing, biofilm development, age of distribution system, and many other variables that could explain inconsistent conclusions in epidemiological results. Even climatic events can play a role by taxing treatment plant operations or increasing the chances for environmental intrusion events.
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The latter resulted in the estimated 11.69 million cases of acute gastrointestinal illnesses per year and a lower estimate of 4.26 million cases per year associated with poor source water quality/poor water treatment. Assumptions include the applicability of the attributable risk percent estimates from the household intervention trials to the entire U.S.
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Using a lab-scaled experimental setup of a distribution system and cross junctions equipped with various pumps and sensors, researchers are evaluating published models on water quality and hydraulic flow behavior of water distribution piping systems under various conditions of hydraulic flow. Studies conclude that previous assumptions of mixing in a distribution system are potentially in error.
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. Viruses present a particular challenge in monitoring water quality due to their small size, low infectious dose, and lack of universal cell culture.
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For quantitative microbial risk assessment, key pieces of information are needed to be either known or predicted, including the infectious dose response of the pathogen of interest; concentration at which the agent can be found in water; the impact of various water treatment strategies on reducing pathogen infectivity; and pathogenicity factors. Values of exposure and doseresponse parameters may correspond to a point estimate of interest.
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Finally, better communication between water quality professionals, public health researchers, and health-care providers is needed to design studies that comprehensively assess the impact of waterborne disease and address the multibarrier approach necessary to preserve water quality. OVERVIEW REFERENCES Aquatest.
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2001. The association between extreme precipita tion and waterborne disease outbreaks in the United States, 1948-1994.
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2006. An approach for developing a national estimate of waterborne disease due to drinking water and a national estimate model application.
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2008. Climate change and waterborne disease risk in the Great Lakes region of the U.S.
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2004. Heavy rainfall and waterborne disease outbreaks: the Walkerton example.
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2006. A role of high impact weather events in waterborne disease outbreaks in Canada, 1975-2001.
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2001. Waterborne disease outbreaks caused by distribution system deficiencies.
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2006. Surveillance for waterborne disease and outbreaks associated with drinking water and water not intended for drinking -- United States, 2003-2004.
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2006. A role of high impact weather events in waterborne disease outbreaks in Canada, 1975-2001.
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2008. Surveillance for waterborne disease and outbreaks associated with drinking water and water not intended for drinking -- United States, 2005-2006.
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