The purpose of this position paper is to guide further debate and decision-making by the American Public Health Association (APHA) on a public policy statement on safe drinking water. This position paper provides the scientific basis and justification for the importance of improving our nation’s drinking water supplies. It also emphasizes the important role that public health practitioners and policy makers can play on this important public health issue. The position statement will enable APHA to become a policy leader for safe drinking water. The objectives of this position paper are for APHA to be well positioned to:
Provide expert guidance to the Environmental Protection Agency on decision-making regarding drinking water standards and regulations;
Improve public health education about drinking water risks, specifically education for public health and health care professionals; and
Promote sufficient funding for federal and state drinking water programs.
II. The Problem - Scientific Basis
In the United States, the quality and safety of our drinking water continues to be an important public health issue. Individuals continue to become sick, develop serious illness, and die as a consequence of drinking contaminated water. It has been estimated that up to 900,000 people fall ill and up to 900 die annually from waterborne infectious diseases in the US.1 Informal Centers for Disease Control and Prevention (CDC) estimates are that 200,000 to 1,300,000 Americans become acutely ill each year, and several hundred die from microbiologically contaminated water. US Environmental Protection Agency (EPA) data suggested that in 1997, almost 30 million Americans drank water from systems that were in violation of public health standards. Clearly, officially recorded cases of waterborne disease represent only the tip of the iceberg.
Most drinking water in the US is obtained from surface or ground water sources, both of which can be contaminated. Surface water from rivers, streams, lakes and ponds is under threat from environmental contamination. This contamination may come from algal growth, geologic formations, point sources (such as industrial or wastewater treatment plant discharges), non-point sources (such as runoff from urban streets, agricultural runoff, etc.) and antiquated infrastructure. Because of this potential level of contamination, surface water usually requires aggressive and sophisticated treatment prior to consumption. Ground water may be contaminated from a number of natural sources including arsenic and radon due to local hydrogeology. In addition, severe contamination of the soil, such as from hazardous waste dumps and leaking underground storage tanks, can result in locally severe ground water contamination. Properly treated water may become contaminated again after it leaves the treatment plant and enters the distribution system due to infrastructure in need of repair. Outbreaks have been associated with contamination of water within distribution systems when sewage from wastewater pipes has entered drinking water pipes through leaks or improper connections.
B. Specific Contaminants of Concern
1. Microbial Contaminants of Concern
The bacteria, viruses, and protozoa that are of major concern in drinking water are usually of fecal origin. Bacterial waterborne pathogens, once the scourge of human urban existence, are now generally controlled by modern water treatment systems. Waterborne disease in the US in general, and bacterial disease in particular, usually occurs when water treatment and/or infrastructure systems fail or when untreated water is consumed. However, viruses and enteric protozoa are more common sources of waterborne disease outbreaks. Norwalk and Norwalk-like viruses, rotavirus, and Hepatitis A are all important viruses transmitted by water.2
Since 1981, enteric protozoa have been the leading cause of waterborne disease outbreaks. The major enteric protozoan, Cryptosporidium parvum, is a parasite commonly found in rivers and lakes, that can make its way into drinking water supplies and can cause severe outbreaks of gastrointestinal illness. Before 1982, the disease was rarely reported, but as the AIDS epidemic increased, so did the number of cryptosporidiosis cases.3 Initially, infection was recognized only in immunocompromised people, but as diagnostic methods improved, outbreaks and other incidences have appeared in the healthy population. Cryptosporidium is considered a major threat to the US water supply, because it is highly infectious, resistant to chlorine, and because of its small size that makes it difficult to filter.4Even a well-operated, modern water treatment system cannot ensure that its drinking water will be completely free of these protozoa.
2. Chemical Contaminants of Concern
Disinfection By-Products: The most ubiquitous chemicals found in treated water are the disinfection byproducts (DBPs) formed by reactions between one and two-carbon organic molecules and added chlorine in water. Trihalomethanes are among the best studied of the DBPs. DBPs have been implicated in both cancer and non-cancer health effects. Comparison of populations consuming chlorinated and non-chlorinated water has shown an increase of bladder and possibly colon and rectal cancer among those consuming chlorinated water.5 In addition, some studies have suggested an increased risk of adverse reproductive outcomes, including spontaneous abortion and neural tube defects.6 Studies indicating an association between DBP exposure and adverse reproductive outcomes have resulted in EPA forming an advisory committee to review the need for additional controls on disinfection byproducts.
Lead: Since the removal of lead from gasoline, drinking water has become a more important route of lead exposure for the general population. Lead generally enters drinking water by leaching from pipes and solder joints. Lead soldering is still commonly used in taps, water coolers, and other fixtures placed between building pipes and the consumer. Brass fixtures, such as spigots, and pumps used for wells may also be made with an alloy that contains lead. Studies of fixtures in offices and schools have shown a potential for high exposures to lead in first-draw samples of water.7 People living in older housing, and those served by delivery systems with lead pipes especially in areas with soft water, are most at risk for ingesting significant amounts of lead through their drinking water.
Other Metals: A variety of other metals, including arsenic, cadmium, and mercury may be found locally in drinking water supplies. Arsenic, in particular, has been found in high levels in community water supplies, usually as the result of high concentrations found in regional geologic formations. Arsenic in drinking water, primarily in countries other than the US, has been associated with bladder, skin, and lung cancers.8 The current EPA drinking water standard was set in 1943 at 50 parts per billion (ppb). The World Health Organization and the National Academy of Sciences (NAS) have concluded that a lower standard is indicated.9
Nitrates: Nitrates contaminate water supplies as the result of ground applications of fertilizers and seepage from septic tanks. Thus, concentrations tend to be highest in rural, agricultural areas and may vary widely depending on the season. The EPA estimates that as many as 52% of community water wells and 57% of domestic water wells in this country are contaminated with nitrates.10 In infants under about four months of age, ingestion of high concentrations of nitrates from well waters results in methemoglobinemia, which carries a 7-8% fatality rate. The United States Geological Service (USGS) has estimated that up to 15% of wells in agricultural and urban areas have nitrate levels exceeding the EPA standard.11
Radon: Radon in water constitutes a threat to health both from direct ingestion as well as from contribution to indoor air levels and inhalation after water is heated and/or agitated, such as during showering. Alpha particles emitted from radon can ultimately cause cancer of the gastrointestinal tract or lung, depending on the route of exposure. Levels of radon vary by source, treatment process and by region. Water from New England, the Southeast, and mountain areas has more radon than other regions.12 The EPA is currently developing standards for radon in drinking water.
Synthetic Organic Chemicals: A variety of pesticides are routinely found in drinking water at very low concentrations. Tetrachloroethylene, also known as perchloroethylene or “perc,” has been found in high levels in water supplies as the result of leaching from recently installed polyvinyl chloride or PVC water mains. Studies of populations exposed through this route have associated perc exposure with lung cancer and possibly colo-rectal cancer.13Migration of fuel-associated chemicals such as benzene and methyl-ter-butyl ether (MTBE) from underground gasoline storage tanks has also been reported.14
C. Susceptible Populations
When considering drinking water quality, it is vital to consider populations that are more susceptible to exposures, including infants/children, immune-suppressed individuals, and the elderly. Neonates, for example are especially at risk for enteroviruses,15 lead and mercury, and nitrates. The immune-suppressed population includes not only people living with AIDS, but also transplant patients, persons undergoing chemotherapy, and those suffering from less common congenital or acquired immune system dysfunction. Cryptosporidiosis is deadly for the immunocompromised. Disseminated Mycobaterium avium complex (MAC) is another common infection in AIDS patients who have CD4 counts less than 100/mm3, and it can also occur in other immunocompromised patients without AIDS. Transplant patients are especially susceptible to developing disseminated adenovirus infections.16 The elderly are at increased risk of infection and disease from microbial contamination because of many factors including, reduced immunity, high incidence of frailty from malnutrition or existing chronic illness, and institutional exposure (e.g., hospitals and nursing homes). They are also at increased risk of dying from waterborne infections. The case fatality rates in nursing homes for certain waterborne pathogens, such as rotavirus and E. coli 0157:H7, can be two orders of magnitude greater than that in the general population.17 Outbreaks of Norwalk virus and other caliciviruses have been frequently reported in nursing homes.
III. Federal and State Regulations and Provisions
It is timely for APHA to be actively engaged in policy activities related to safe drinking water. There are weaknesses in federal statutes and regulations governing the safety of drinking water, and a number of EPA standards are being currently being reviewed and revised. In some instances, contaminants are not regulated, such as radon and a number of pesticides. A few EPA standards have not been updated for decades, such as arsenic, and current scientific studies indicate that current standards may not sufficiently protect public health. EPA standards may protect the average adult but may not protect vulnerable populations, such as infants and children, the frail elderly, and those with weakened immune systems. Moreover, EPA standards are established to protect health while considering the water treatment costs and availability of clean-up technology.
One of the important public health provisions in federal legislation is to ensure the public’s right to know what is in their drinking water. Under the Safe Drinking Water Act (SDWA) Amendments of 1996, water utilities are required to issue Consumer Confidence Reports (CCRs) or right-to-know reports, which disclose results of monitoring for regulated contaminants. The CCRs are good informational tools, but they do not give the consumer the full picture on drinking water quality, and are shown to have important limitations. For example, CCRs only provide information to people drinking from community water supplies, however it is estimated that 9% of people in the US (about 24 million) get their drinking water from private wells or other individual systems. Only levels for regulated contaminants are reported, and some important contaminants are not regulated.
EPA and state regulatory agencies need guidance from public health experts on the setting and implementation of drinking water standards. For example, public health expertise is greatly needed on setting appropriate standards for chemical and microbial contaminants, ensuring the protection of vulnerable populations, protecting drinking water sources, evaluating risk trade-offs between contaminants and between controlling contaminants and controlling costs, and participating in the broader public disclosure about drinking water quality.
IV. Goals for APHA
The American Public Health Association seeks to promote the basic right of all people and all communities to safe and affordable drinking water. APHA will work:
To foster greater involvement of the public health professional as advisor, educator, and advocate on issues related to drinking water and health;
To promote understanding in public health practice and policy making of the potential public health impact of drinking water contamination;
To ensure broader public access to information on drinking water quality, including improvements in the consumer right-to-know provisions that will inform everyone of their drinking water quality;
To encourage public health departments to prepare response plans for drinking water contamination;
To call for greater accountability of EPA and state regulatory agencies in the prevention of waterborne diseases, especially among susceptible populations;
To promote increased federal funding for research on links between drinking water contamination and disease, as a foundation for informed standard-setting; and
To support increased funding for public health departments and other interested non-governmental entities to educate the public about drinking water quality and to be prepared for public health emergencies related to drinking water.
- Microbial Pollutants in our Nation’s Water. 1999; ASM: Washington, DC.
- Moe Manual of Environmental Microbiology, Washington, DC: American Society of Microbiology, 1997.
- Guerrant RL. Cryptosporidiosis: An emerging and infectious threat. Emerging Infectious Diseases. 1997;3(1).
- Morris et al. Clorination and chlorination by-products and cancer: A meta-analysis. Am J Public Health. 1992:82:955-963.
- Deane et al. Epidemiol. 1992; 3(2):94-97; Klotz and Pyrch. Epidemiol. 1999; 10(4):383-390.
- Maas et al. Am Ind Hyg Assoc J. 1994; 55(9): 829-832.
- Kurttio et al. Environ Health Perspect. September 1999; 107(9): 705-101; Smith et al. Am J Epidemiol. April 1998;147(7):660-669.
- World Health Organization, Arsenic in Drinking Water. February 1999.
- Http://www.epa.gov/seahome/groundwater/src/overview/htm. Accessed 1/31/00.
- The Quality of Our Nation’s Waters, 1999. US Geological Survey. http://water.usgs.gov/pubs/circ/circ1225. Accessed 2/17/00.
- Risk Assessment of Radon in Water. Washington, DC: National Academy of Sciences, 1999.
- Paulu et al. Environ Health Perspect. 1999; 107:265-271.
- Stern and Tardiff. Risk Anal. December 1997: 17(6):727-43.
- Abzug, Human Enterovirus Infections. Washington, DC: American Society of Microbiology, 1995. Dagan, Pediatr Inf Dis J. 1996;15:67-71.
- Hierholzer. Clin Microbiology Rev. 1992;5:262-274.
- Gerba et al. 1996.