A much smaller number of systems were cited for high levels of arsenic, lead or copper, or nitrates. And patterns have shifted over the years as regulations have changed. In the early years of the study, California’s Central Valley farm belt used to post high numbers, particularly for nitrogen compounds, but that changed after tighter regulations took effect.
Today, the “hot spots” tend to be in the Midwest and southern Plains states. Currently, systems in Texas, Oklahoma, and Idaho are racking up the most violations.
“Another trend I found was that these places that are hot spots of violations and have increased time trends also have repeat violations,” Allaire said. “In a given utility, year after year, there are some utilities that continue to not meet national level standards, and that’s kind of concerning.”
While the study doesn’t delve deeply into the causes, Allaire said the source water in those areas, particularly in Oklahoma, is rich in organic material — including livestock manure. The states have high summertime temperatures. Those can combine to produce more disinfection byproducts, and the systems may not be treating their lines to counter that process.
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Smaller systems may need to consolidate with their neighbors or combine resources in other ways to improve their processes and reduce their violations, she said. And privately run systems had a narrow advantage over publicly operated ones.
“These larger private firms have a lot at stake if they’re serving their customers with poor quality of water,” she said. “They face this risk they could be taken over by the local municipality or they could be slapped with lawsuits.”
Contaminated water has been blamed for up to 16 million yearly cases of gastroenteritis, an intestinal inflammation that causes nausea, vomiting, and diarrhea. Pollution or improper treatment can lead to crises like what happened in Flint. And other pollutants can cause long-term, chronic ailments like cancer or neurological diseases.
Allaire found the number of violations doubled over the course of the study period, mostly as regulations have grown to cover more pollutants — currently 91, up from 22 when Congress passed the Safe Drinking Water Act in 1974.
The findings were published February 12 in the research journal Proceedings of the National Academy of Sciences. If you’re curious about your own town, Allaire said, the EPA allows you to look up your local water service in its Safe Drinking Water Information System.But don’t be surprised if nothing turns up, she added.
“In general, the US has some of the best water quality in the world,” she said.