Arsenic is another common contaminant to groundwater, and a big problem worldwide. As Katy Daigle states, “Arsenic-laced groundwater has been found in at least 30 countries, from Argentina to China, Cambodia and Vietnam, as well as parts of Canada and the U.S.” (Daigle, 2016, p. 44) Since arsenic can typically be filtered out of water with basic equipment, it’s a bigger problem in poor areas of the world, yet people in the U.S. are hardly immune.

Where does arsenic come from, and how does it get into the water?

Unlike many of the other toxins discussed, arsenic is typically a natural contaminant. It can be found at various levels in the subterranean earth underneath us. Arsenic can spread throughout underwater aquifers, so it is often a man-made disaster as well, created by improper drilling techniques or poor water planning. Arsenic-contaminated water “can move horizontally, from one dirty aquifer to a neighboring clean one,” says Daigle, “as well as up and down if the water pressure between the two reservoirs changes.” (ibid, pp. 50-51)

How much arsenic in water is safe?

The World Health Organization says arsenic is dangerous at concentrations above 10 micrograms per liter. But once again, there’s many scientists who would say this number is too high, pointing to research showing adverse health effects at much lower levels.

The health effects of drinking arsenic-contaminated water

Arsenic is a poison that affects just about every system in the body, so the range of potential consequences are almost unlimited. Arsenic has been found to “cause learning disabilities in concentrations as low as 50 parts per billion – a level that’s not uncommon in wells.” (Heyworth, 2011) A 2001 statement by the National Academy of Sciences also warns that “the data indicate arsenic causes cancer in humans at doses that are close to the drinking water concentrations that occur in the United States.” (Vandiver, 2004) So people here in the U.S. aren’t immune, and it’s yet another reason families drinking well water might want to invest in a basic water filtration system.