Iowa Private Rural Drinking Water Well Study Results Released

Nov. 18, 2009
Study shows continuing problems with nitrate and bacterial contamination

The newly released Iowa Statewide Rural Water Well Survey Phase 2, which examined the water quality of private rural drinking water wells, shows continuing problems with nitrate and bacterial contamination.

The survey, which was led by the University of Iowa Center for Health Effects of Environmental Contamination, also reveals that a high percentage of wells statewide were contaminated with arsenic.

"The nitrate and bacteria results were expected despite efforts to address contamination in groundwater sources,” said Peter Weyer, Ph.D., the study's lead investigator and associate director of the UI Center for Health Effects of Environmental Contamination. “The arsenic results were something we did not expect. Nearly half the wells sampled had some level of arsenic, and 8% of those had a level that could be considered a health concern.

"On a more positive note, the levels of the commonly used herbicide atrazine seem to be trending downward from what past studies have shown.”

The survey, conducted from 2006 to 2008, sampled 473 wells statewide for bacteria, nutrients, metals, common use herbicides and insecticides and herbicide degradates. This study was a follow-up effort to the original Statewide Rural Water Well survey, which was conducted from 1988 to 1989.

Additional findings from the sampled wells in the latest study include:
• 43% of the samples had total coliform bacteria, 19% had enterococci and 11% had E. coli;
• 49% had nitrate, with 12% having more than 10 parts per million of nitrate-N, which is the Safe Drinking Water Act standard for public water supplies; and
• 48% had arsenic, with 8% having arsenic above the Safe Drinking Water Act standard for public water supplies.

"While the herbicide degradates are widespread, most of the detection levels are very small--in the sub-part per billion range," Weyer said. "In addition, there are no drinking water standards established for these breakdown products."

Degradates are generally believed to be less toxic than the parent compound.

Source: University of Iowa