U.S. Communities Unequally Exposed To Arsenic in Drinking Water, Study Finds

Despite efforts to reduce the amount of arsenic in drinking water systems across the U.S., not all communities have benefited from these efforts equally.

A study published in the journal Environmental Health Perspectives earlier this month describes the regions in which arsenic remained prevalent in public drinking water supplies after the Environmental Protection Agency (EPA) adjusted its regulations in 2006. Researchers found that smaller communities in the Southwest, places reliant on groundwater systems, and Hispanic communities were more likely to have continued high levels of arsenic contamination.

The study is the first to assess differences in public drinking water arsenic exposures by geographic subgroups. Before 2001, the maximum allowable contaminant level for arsenic was 50 micrograms per liter. In 2006, the EPA enforced the new regulation, decreasing the maximum contamination level from 50 to 10 micrograms per liter.

The findings can help public health researchers and regulatory agencies like the EPA understand the efficacy of new water regulations and target regions continuing to exceed the maximum contamination levels.

“This is a critical question in thinking about environmental justice and injustice,” Anne Nigra, a graduate student at Columbia University in New York and primary author of the paper, tells Verywell. “It’s important in thinking about targeting public health interventions and additional support and regulatory enforcement to make sure we don’t have any communities in the U.S. that are at problematic levels of arsenic in drinking water.”

A Dangerous Contaminant

Arsenic is the most significant chemical contaminant in drinking water around the world, reports the World Health Organization. The inorganic arsenic compounds found in drinking water can be highly problematic to human health, and chronic exposure can cause skin lesions and skin cancer among other problems.

Arsenic can enter groundwater systems naturally when it dissolves from certain rock formations. Agricultural and industrial processes such as copper smelting and mining can also release arsenic into the environment, where it can remain for a long time, according to the Centers for Disease Control and Prevention (CDC).

“There is no safe level of arsenic exposure,” Nigra says. “We know that even at these lower to moderate levels of arsenic exposure, we have increasing evidence of arsenic’s impact on a variety of adverse health effects, including cardiovascular disease, low birth weight. But the most concerning outcome for arsenic, of course, is cancer.”

The Research

The research team sought to estimate the level of arsenic exposure in water systems across the U.S. and to locate exposure inequalities between communities. They used data from the EPA’s six-year review contaminant occurrence data set to estimate arsenic exposure in public water systems. The data tracks more than 36,000 community water systems, representing 98% of all community water systems in the country, from 2006-2008 and 2009-2011.

Nationwide, arsenic concentrations declined by 10.3% and 11.5% during these two time periods. Community water systems that had high concentrations across both periods were 61% more likely to be in the Southwest, 95% more likely to be served by groundwater and 38% more likely in regions serving Hispanic communities. Additionally, water systems serving smaller populations (on average 1,102 people) were more likely to have high arsenic concentrations.

Nigra says her team observed a decline in arsenic concentration levels in many water systems across these time periods. In New England, for example, there was a 37% decrease between 2006 and 2011.

“Across the U.S., average arsenic concentrations decreased by about 10% which is wonderful, and which is very, very meaningful,” Nigra says. “We also found that water systems that at baseline had higher levels of water arsenic did see larger absolute reduction over time. That’s also great news because it means that this intervention—the change in the regulatory limit—really targeted the kind of worst cases.”

The research team also identified different sociodemographic subgroups. They found that Hispanic semi-urban communities saw the highest sustained levels of exposure of all groups.

Nigra says that Hispanic communities are actually doubly impacted by arsenic exposure. In addition to the higher prevalence of the contaminant in drinking water systems, these communities may ingest more arsenic through their food compared with other groups. This is because rice, a dietary staple for many Hispanic and Latinx people, accumulates arsenic and is the major source of the contaminant in food.

“We’re building this very troubling picture where semi-urban Hispanic communities, especially those in the Southwest, not only are they getting elevated arsenic exposure from their diet but now we have this data that indicate they are also exposed to elevated arsenic levels in their drinking water,” Nigra says. “That’s a real issue moving forward because frankly the research on Hispanic and Latinx communities when it comes to arsenic exposure is lacking.”

Amending Inequalities

When the EPA sets regulatory standards, it must consider the economic impact and feasibility of creating water treatment services to meet the new restrictions. Nigra says that because of this, the maximum contamination level is often greater than what is best for public health. 

States are able to set their own, stricter, regulatory measures. New Jersey and New Hampshire, for example, have a maximum contamination level of 5 micrograms per liter, compared to the federal limit of 10 micrograms per liter.

“We know that the economic benefit of reducing arsenic and lead exposure in drinking water far outweighs the cost to implement those reduction strategies,” Nigra says.

Moving forward, she says it’s important to continue researching and implementing strategies to decrease exposure inequalities.