Pilot Study Provides Information on Contaminant Exposure from Tap Water at Residential and Workplace Sites in the United States

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The U.S. Geological Survey (USGS), in collaboration with National Institutes of Health, U.S. Environmental Protection Agency, and academia, completed a pilot study to provide information on contaminant exposure from tap water at 26 locations including public and private supplies. Public-supply tap water generally met enforceable standards for those compounds with standards. Samples consisted of contaminant mixtures that are not commonly monitored and for which the health risks are unknown.

In our daily routines, we are exposed to numerous hazards including microbial and chemical contaminants in food, air, recreational water, drinking water, and through human contact that may or may not pose substantial health risks. The overall contribution of drinking water to the total risk of disease from all sources is not currently known.

With the declining frequency of high-mortality events in the United States during the last 100 years owing to pathogens in drinking water, public concern has increasingly focused on chemical contaminants in water such as those that enter public water supplies through source waters or are intentionally added to the supply for disinfection.

The current safety and long-term sustainability of U.S. tap waters are rising public health concerns for several reasons, including aging drinking water infrastructure and high-visibility events such as the Flint, Michigan, lead crisis.

Consumers in the United States expect safe drinking water at the point-of-use (tap water). Ensuring safe drinking water through disinfection and monitoring of public water supplies is a priority of drinking water utilities, State and local health agencies, and the U.S. Environmental Protection Agency under the Safe Drinking Water Act. Regulated chemicals are routinely monitored at drinking water facilities prior to distribution; however, only select chemicals (for example, disinfection byproducts, disinfectant residuals, lead, and copper) are routinely monitored in tap water where there is exposure.

USGS scientist sampling tap water from a public water supply

USGS scientist sampling tap water from a public water supply.  (Credit: Edward Furlong, U.S. Geological Survey. Public domain.)

The lack of information on chemicals in tap water is a gap for understanding exposure.  Water chemistry can change between the finished water distributed from the drinking water facility and the tap owing to leaks, cross-connections, back-siphonage, and corrosion in the distribution system. Likewise, improved understanding of contaminant exposures in U.S. self-supplied tap water is critical because more than 40 million people in the United States depend on private wells for drinking water that are not regulated as part of the Safe Drinking Water Act.

Therefore, the USGS, in collaboration with National Institutes of Health, U.S. Environmental Protection Agency, and academia, tested tap water from selected homes and offices across the Nation to help fill these gaps. Tap water samples were collected from 12 workplaces (11 municipal sources and 1 water cooler) and 13 homes (7 municipal sources and 6 private wells). Nineteen inorganic and 482 organic compounds were analyzed. Most of the organic compounds are not regulated by the Safe Drinking Water Act.  
The team detected 75 organic and 18 inorganic compounds at least once in the study. No water samples drawn from public supplies exceeded any enforceable drinking water standards (one water sample drawn from a privately owned well exceeded the maximum recommended amount of uranium).  The organic compounds detected included perfluorinated compounds, pesticides, pharmaceuticals, and numerous byproducts of typical water disinfection processes, such as chlorination.  Disinfection byproducts were present in all public-supply samples and accounted for almost all the cumulative concentrations of organics detected in public-supply tap water.  

The results of this study are consistent with a regulated drinking water supply; however, researchers point out that many chemicals detected in this study are not regulated and are never monitored at the tap.  The researchers also note that little is known about the cumulative health effects of exposure to these mixtures of contaminants. This study provides important baseline data for public health experts to better understand exposure to contaminants through drinking water. This information is critical to begin to reduce uncertainties associated with setting priorities for drinking water infrastructure improvements. 

This work by the USGS Environmental Health Program's Infrastructure Team builds on decades of USGS expertise and laboratory capabilities in contaminant fate and transport science and fills substantial gaps in existing data, data, given that  monitoring of tap water is limited for public supplies and not required for private supplies.

This study was funded by the USGS Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology).