Arsenic in Rural Oregon

Illustration by Lauren Smitherman and David Reinert
The Harney basin features complex volcanic geology and a closed hydrologic system. (Illustration by Lauren Smitherman and David Reinert)

By Nick Houtman

When it comes to water, Lauren Smitherman doesn’t mind getting a little personal. As a graduate student in Water Resources Science at Oregon State University, she asked people in rural Oregon for permission to collect samples of their drinking water. Assured of confidentiality, most people welcomed her into their kitchens where Smitherman ran a stream of cold water from their faucets for a few minutes before filling a plastic bottle.

Lauren Smitherman
Lauren Smitherman

The student researcher was looking for arsenic, the tasteless, odorless element that, in high enough doses and over a long period of time, can cause preterm birth, skin lesions and different types of cancer. It’s the same contaminant that has poisoned thousands of people in Bangladesh and other parts of the world. In the American West, it shows up in groundwater from Arizona to Idaho and Southern California to Oregon.

Smitherman wanted to learn more about the origins of the toxic metal and to evaluate the reliability of two over-the-counter arsenic detection kits. Such kits are potentially useful because the only way to know if the element is present is to test for it. She received financial support from Oregon State’s Institute for Water and Watersheds through a gift from the estate of Paul Peyron of Baker City

Working with Molly Kile, assistant professor of public health, Smitherman first traveled to Harney County to help with an arsenic awareness workshop held by the local health department. Kile is studying the health impacts of low-level arsenic exposure, and the health department runs domestic well-water safety programs that help homeowners test their water for arsenic and interpret the results.

Smitherman and Kile talked with landowners about the health impacts of arsenic, and Smitherman collected samples from wells used for domestic, agricultural and livestock purposes. She also looked for associations between arsenic and aquifers, the water-bearing soils and rocks that supply the county with most of its potable water.

Altogether, she analyzed data from 140 wells ranging from 20 to as much 2000 feet deep. Most were less than 500 feet.

No Single Source

“Arsenic is widespread throughout the region, but there is no one aquifer that is more contaminated than another,” says Smitherman. “In every aquifer I identified, there were some samples that contained arsenic concentrations above the MCL (the U.S. Environmental Protection Agency’s maximum contaminant level, 10 parts per billion). It’s broadly distributed.”

“There was no discernable pattern that would allow us to predict a hotspot,” adds Kile. “That is why it is so important that homeowners test their drinking water. If arsenic is detected, the homeowner can install a water-treatment system, such as reverse osmosis, that would remove it.”

While two-thirds of Smitherman’s samples contained arsenic concentrations below the MCL, 11 percent exceeded 50 parts per billion, the MCL in effect until 2002, which is more than five times the current standard for drinking water. The rest, 21 percent, fell between 10 and 50 parts per billion. The study identified arsenic concentrations from 0 to 153 parts per billion.

“I took a hydrologic approach to this issue,” says Smitherman, “but I also hope that my work is useful for people in protecting their own health. Private wells are not required to be tested for arsenic, so it’s up to the owners to decide what they want to do.”

Private wells are not regulated by safe-drinking-water laws unless the property is being sold. In 2010, the Oregon Legislature required that when a property sale occurs, any well that supplies drinking water must be tested for arsenic, nitrate and coliform bacteria and that the results must be disclosed to the buyer.

Arsenic 101

A little chemistry is useful in understanding what Smitherman did in the lab. Multiple forms of the element can exist in a single sample, so she ran analyses for all chemical forms to determine what chemists call “total arsenic.” Smitherman used a device known as an inductively coupled plasma mass spectrometer in Oregon State’s W.M. Keck Collaboratory for Plasma Spectrometry to quantify the amount of arsenic present.

She also evaluated the accuracy of two kits available to the public for testing arsenic at home. Her results showed significant discrepancies from laboratory results, she says. It’s possible that iron and sulfur compounds in the samples interfered with the tests.

Subsequently, people who want to have an accurate result should use an accredited analytical laboratory, adds Kile. “Fortunately, the Oregon Health Authority’s Domestic Well Safety program has an excellent list of resources for people who want to learn more about this issue.”

Smitherman grew up in Austin, Texas, and received a bachelor’s degree in Environmental Science and Policy from St. Edwards University. She worked for the Texas Commission on Environmental Quality before coming to Oregon State.

Her master’s thesis, Forensic Hydrogeography: Assessing Groundwater Arsenic Concentrations and Testing Methods within the Harney Basin, Oregon, is available in OSU’s Scholars Archive, A white paper summarizing her study is available through the Institute for Water and Watersheds,

She will also be reporting her results at the next Harney County Watershed Council meeting in Burns on November 17.