Ground water is vulnerable to contamination from activities occurring on and below the earth’s surface.
Image courtesy of US EPA website.
A new study of small drinking water systems in Wisconsin shows residents of some communities in the state are exposed to viruses, including norovirus, through tap water. Researchers found human viruses in about 24 percent of water samples tested in 14 communities that do not disinfect their ground water.1 The state does not require drinking water disinfection. Levels of viruses correlated to the incidence of gastrointestinal illness.
The viruses, which originate in human waste, are believed to enter groundwater through leaking wastewater sewers. Easily destroyed by routine water disinfection, the viruses persist in non-disinfected water.
According to the Milwaukee-Wisconsin Journal Sentinel online, drinking water disinfection is not required for 66 Wisconsin municipalities serving about 85,000 people. Nationwide, over 95,000 systems serving 20 million users do not disinfect their water. The new study begs the question: How many US communities are unknowingly using water of poor quality that could be improved with disinfection?
Science and Public Policy
Just over a year ago the Wisconsin state government rejected a rule requiring municipal governments to disinfect drinking water, citing budget concerns. Defenders of the action prefer to leave the choice of disinfecting up to local governments rather than impose a mandate. Yet, the new virus study shows that contamination can be insidious. In addition to the leaking wastewater sewers noted in this study, other studies (see, for example, this U.S. Geological Survey report) have found septic tanks may contaminate drinking water with viruses under certain geologic conditions.
The nation’s aging infrastructure includes many leaking wastewater sewers, and leaking and cracking water and sewer pipes provide opportunities for cross-contamination. By adding disinfectant, these problems can be addressed. Monitoring the residual presence of chlorine disinfectant, for example, throughout a distribution system provides a means of detecting points of contamination. From that perspective, does it make sense for communities to bypass disinfection—a step that prevents contaminants from reaching our glass of water?
EPA Paying Attention
The Environmental Protection Agency (EPA) amended the Safe Drinking Water Act in 1996 to increase protection against microbial pathogens in public groundwater systems. The 2006 Ground Water Rule requires municipalities to take a targeted, risk-based approach to protecting public health, but does not require all groundwater systems to disinfect their water. The virus study should be used to inform that risk-based approach.
Last month EPA published a list of 30 contaminants, including two viruses—enteroviruses and norovirus—that some 6,000 public water systems will be tasked with monitoring from 2012 to 2015 as part of the Unregulated Contaminant Monitoring Rule. The monitoring results will help EPA determine whether any of these additional substances need regulating.
Drinking water disinfection is one of the most critical underpinnings of public health protection. The Wisconsin virus study demonstrates that groundwater treatment could be more beneficial than was once thought. The study should spur public officials to consider these populations and do the right thing.
If you would like to have your tap water tested for virus contamination, contact your local water utility, state health department or state department of the environment.
Joan B. Rose, PhD, is the Homer Nowlin Chair in Water Research at Michigan State University and a member of the Water Quality and Health Council.
1Wisconsin communities studied were: Crandon, Cumberland, Barron, Chetek, Ladysmith, Tomahawk, Prairie du Sac, Adams, Spring Green, Rice Lake, Cameron, Baldwin, Lake Hallie and Fall River.