The Montana Department of Public Health and Human Services believes that high levels of arsenic recently detected in several Charlo-area wells were naturally occurring.
Arsenic occurs naturally in the earth’s crust and has been linked to several health problems, including cancer.
The U.S. Environmental Protection Agency has set a safe exposure limit of 10 parts per billion in water.
After a Charlo family’s well tested above that level in December, the Departments of Environmental Quality and Public Health and Human Services notified 89 homeowners within a three-mile radius to offer free testing.
Provided to the Missoulian by Diana Luke, program director of Lake County Environmental Health, it stated that “we believe that the arsenic is most likely natural and comes from geologic sources.
The water in this aquifer is naturally low in oxygen, and this chemical environment tends to liberate and mobilize certain natural elements.
For example, many residents have iron treatment on their water systems.” Earlier this month Ken Crisp, the owner of a Missoula water-technology firm involved with this issue, had also surmised that it was naturally leaching from deep sediments.
Out of 38 samples analyzed as of Feb. 8, the state found that 84 percent had arsenic levels above the state limit.
It did say, however, that the area’s public water supply remained safe to drink.
It advised area residents to test their drinking water source for this substance, and said that free testing would be available until March 15.