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Drinking Water Contaminants - America's Children and the Environment: A First View of Available Measures
The contaminants in drinking water are quite varied and can cause a range of diseases in children, including cancer, developmental effects such as learning disorders, and acute diseases such as gastrointestinal illness. Children are particularly sensitive to microbial contaminants because their immune systems may be less well developed than those of most adults. Children are sensitive to lead, which affects brain development, and to nitrates, which can cause methemoglobinemia (blue baby syndrome).
EPA sets drinking water standards for public water systems, referred to as Maximum Contaminant Levels (MCLs). These standards are designed to protect against adverse health effects from contaminants in drinking water while taking into account technical feasibility of meeting the standard. MCLs have been adopted for more than 80 microbial contaminants, chemicals, and radionuclides. EPA also adopts standards for the protection of drinking water sources and for the treatment of drinking water to increase its safety. An important treatment-related standard, the Surface Water Treatment Rule, requires treatment of surface water by filtration to remove contaminants.
In 1998, EPA established more stringent filter performance requirements to further strengthen microbial protection. In the same year, EPA also established new drinking water standards for disinfection byproducts, exposure to which has been associated with long-term bladder cancer and possible reproductive effects. Most recently, EPA finalized standards protecting against radionuclides in drinking water. Because these standards have been promulgated only recently, this report does not reflect the increased public health protection achieved through their implementation.
Exceedances of Drinking Water Standards
One way to measure children's risk of exposure to contaminated drinking water is to identify public water systems that contain contaminants at levels greater than those allowed by the drinking water standards. Ideally, we would look at data on concentrations of all of the chemical and microbial contaminants in all public drinking water systems and identify any areas of risk for children. This is not currently possible, for two reasons. First, the national data systems for drinking water do not track concentrations of contaminants in drinking water, but rather the frequency with which standards are exceeded. Second, the information on violations is incomplete because not all public water systems fully monitor contaminants or report their monitoring results. (We do, however, have some data that identify the public water systems that do not monitor or report their results.)
We can use information about violations as a surrogate for exposure to unacceptably high levels of drinking water contaminants. We also need to consider information about water systems that do not monitor or report results, because we do not know with certainty whether populations served by these systems are at risk.
Data are available only for public water systems. Approximately 42 million people are served by private drinking water systems, which are not required to monitor and report the quality of drinking water. We do not have information to indicate whether these people are at risk.
- The percentage of children served by public water systems that exceeded a Maximum Contaminant Level or violated a treatment standard decreased from 19 percent in 1993 to 8 percent in 1998.
- Every category of violation decreased between 1993 and 1998. The largest decline was for violations of the microbial contaminants standards.
- A violation of "treatment and filtration" is defined as any failure in the treatment process, or in operation and maintenance activities, or both, that may affect water quality. EPA has a rule that specifies the type of treatment and maintenance activities that systems must use to prevent microbial contamination of drinking water.
- Data on violations reported to the federal government are of generally high quality. However, many public water systems fail to report all violations. A recent review of the data concluded that 68 percent of the microbial contaminant violations are reported, 19 percent of the violations for other contaminants are reported, and 11 percent of the treatment and filtration violations are reported.31
Nitrates and Nitrites
High levels of nitrites or nitrates in the water supply can interfere with infants' ability to absorb oxygen and can lead to "blue-baby" syndrome (methemoglobinemia), which can result in death. EPA has set drinking water standards for nitrates and nitrites.
The percentage of children living in areas served by public water systems that violate these standards can be used as a measure of risk of exposure to nitrates and nitrites. However, some families are served by water supplies, such as wells, that are not included in this measure because they are not part of public water systems and are not subject to monitoring. Many people served by private water supplies live in rural and agricultural areas, and may be at particular risk. Fertilizer and livestock manures are significant contributors of nitrates and nitrites in groundwater supplies of drinking water.
- In 1993, approximately 147,000 children were served by public water systems that violated the nitrate or nitrite standard. In 1998, 117,000 children were served by systems that violated the nitrate or nitrite standard.
- The primary sources of nitrates include livestock manure (especially from feedlots), fertilizers, and human sewage.
Monitoring and Reporting
Public water systems are required to monitor for contaminants and report violations of drinking water standards to EPA. However, not all public water systems conduct all required monitoring and report violations. Such water systems violate monitoring and reporting requirements.
Some monitoring and reporting violations, such as late reporting, are minor. But some water systems have major violations, such as failing to collect any water samples during a specified monitoring period. Children that live in areas that are not adequately monitoring for water contaminants may be at risk, but the extent of the risk is unknown.
- In 1993, approximately 21 percent of children lived in an area served by a public water system that had at least one major monitoring and reporting violation. This figure decreased to about 10 percent in 1998.
- The largest number of monitoring and reporting violations occurred for the lead and copper standards. Approximately 11 percent of children in 1993 were served by public water systems with monitoring and reporting violations for lead and copper, decreasing to about 5 percent in 1995. The number has remained constant since then.
- The percentage of children who live in areas with a major chemical and radiation monitoring violation declined from approximately 9 percent in 1993 to about 2 percent in 1998.