Arsenic is a natural element that is found in soil and minerals, however, it can cause many health problems, and high levels of exposure can even cause death.
Previous research in South Asia showed that exposure to arsenic in drinking water harms children's intelligence, but this study is the first to look at the issue in the United States.
The new study included 272 children in grades 3 through 5 who were given a standard intelligence test. The youngsters lived in three school districts in Maine where household wells are the main source for drinking and cooking water.
The investigators found that exposure to arsenic in well water was associated with lower intelligence scores. However, this link does not prove a cause-and-effect relationship.
Specifically, children exposed to well water with arsenic levels of 5 parts per billion showed significant declines in intelligence that could result in problems in the classroom, the study authors reported in the April 1 online edition of the journal Environmental Health.
In the study, the average water arsenic levels were 9.88 micrograms per liter (mcg/L), and nearly one-third of samples exceeded the maximum 10 mcg/L guideline of the U.S. Environmental Protection Agency and the World Health Organization. The highest level was 115.3 mcg/L.
The strength of the link between arsenic and lower intelligence is similar to that seen with lead, which is known to reduce intelligence, according to study leader Joseph Graziano, a professor of environmental health sciences at Columbia University.
"Even though purchasing a standard filter at the hardware store is inadequate for treating well water, the good news is that there are steps one can take to ameliorate the situation," Graziano said in a university news release.
Installing what's known as a "reverse osmosis system" can lessen the effects of arsenic in drinking water, he said, although it is costly to do so. Education programs about arsenic exposure are being offered to families in the Maine school districts that were included in the study, Graziano added.
The U.S. Environmental Protection Agency has more about arsenic in drinking water.