Many of us who have the privilege of being serviced with supply of safe, treated drinking water tend to take our clean water for granted. But not all Americans get their drinking water from a source that is treated; over 44 million US residents obtain their drinking water from private drinking wells, which mostly go unregulated.

A report which was recently published in the American Chemistry Society's journal, Environmental Science & Technology, has revealed that around 2 million of those people are in danger of being exposed to dangerous levels of arsenic — a toxic contaminant that is found naturally in the environment — through their drinking water supply.

A silver / arsenic rock

Arsenic is a drinking water pollutant that occurs naturally in soils, and is widespread within the environment. Exposure to inorganic arsenic over an extended period of time can potentially result in a wide range of health issues, and has also been linked to varies forms of cancer. Recent studies also suggest that low-level arsenic exposure in pregnant women can have a negative effect on fetal growth and can cause pre-term births.

While municipal water utilities typically have water filtration plants that remove arsenic from water, and need to monitor water for arsenic in order to meet regulatory standards, residents who depend on wells for their drinking water are pretty much left on their own. The onus rests on well owners to monitor their water for contaminants, and if any are found, they are responsible for implementing measures to remove these contaminants. To date, nobody has really focused on who may be getting exposed to unsafe levels of arsenic in their drinking water around the country. This study, conducted by Joseph Ayotte together with a team of fellow researchers from the US Geological Survey (USGS) and the US Centers for Disease Control and Prevention aims to fill that void.

Private drinking water well next to an oil tank.

In order to map out drinking well arsenic levels, the researchers developed a computer model that incorporated existing data of arsenic levels in drinking water wells around the country. They also took into account factors that can affect the concentrations of arsenic, such as aquifer chemistry, geology, and regional rainfall. The model pin-pointed potential arsenic hotspots which were likely to contain wells that had elevated levels of arsenic exceeding the 10 microgram per liter safety limit for drinking water set by the EPA. Hotspots were mostly concentrated around southern Texas, the Southwest, a stretch of land in the upper Midwest and New England. Based on the areas identified, the researchers estimate that the wells affected provide around 2.1 million Americans with drinking water. Many of the affected people may be unaware of the potential risk these contaminated wells pose to their health.

The researchers conclude by warning private well owners to have their water supply tested for arsenic, and to take the necessary precautions to prevent exposure to this potentially harmful contaminant. A home drinking water filter fitted with a filter that is capable of removing arsenic is a simple mitigating measure that will render your water safe to drink.

Journal Reference

Joseph D. Ayotte et al. Estimating the High-Arsenic Domestic-Well Population in the Conterminous United States. Environ. Sci. Technol., October 18, 2017 (web), DOI: 10.1021/acs.est.7b02881