'Safe' Tap Water Contaminant Levels In US May Still Lead To Cancer

Environmental Working Group, a research and advocacy activist group, has published a new peer-reviewed study that looked at the combined cancer risk associated with nearly two dozen contaminants found in tap water. According to the findings, these contaminants may be responsible for thousands of cancer cases in the United States every year. The work is unique because it looks at the cumulative effect of these contaminants instead of assessing them individually.

When officials look at the potential consequences of air pollution, they assess the risk based on exposure to all of the contaminants rather than each individual pollutant. When similar assessments of water are made, however, the Environmental Working Group points out that research tends to focus on the potential consequences of each contaminant. This is a problem because — as with air — people who drink water are exposed to the full roster of pollutants, not just one or two of them.

The new study looked at the cancer risk of exposure to 22 carcinogenic contaminants that were identified in samples taken from 48,363 water systems throughout the United States. These systems feed the taps at homes across the country, delivering the water that most people drink without any additional filtering or treatments. The researchers didn't look at water samples from private drinking wells.

This is the first time researchers have used national drinking water data to assess the overall health impacts of exposure to these nearly two dozen contaminants. The team found that more than 100,000 cancer cases in the US over the course of an average 70-year lifetime can be attributed to the contaminants.

The contamination comes from certain naturally occurring substances, including arsenic, as well as radioactive elements like radium and uranium and byproducts from disinfection. The study found that the water systems that presented the greatest risk were ones that usually relied on groundwater and served smaller towns and cities. The researchers note that the contaminants found in these water systems are below the legally acceptable thresholds in the vast majority of cases.

The group notes that anyone concerned about contaminant exposure can use filters that target these contaminants.