Iowa’s rural private drinking water wells “have several contaminant problems, some long-standing and some emerging,” according to the results of a two-year study released last week.

The study, Iowa Statewide Rural Water Well Survey Phase 2, was led by the University of Iowa Center for Health Effects of Environmental Contamination. It followed up on the results of a similar study conducted in 1988 and 1989 and concluded that many of the problems of 20 years ago remain today.

Scientists who tested samples from Iowa rural drinking water wells discovered that 48 percent had arsenic, with 8 percent containing it at a level above the Safe Drinking Water Act standard for public water supplies. Wells with high arsenic contamination (greater than or equal to 0.01 mg/L) are marked in red on the above map. The blue marks are wells that had low levels.

Scientists who tested samples from Iowa rural drinking water wells discovered that 48 percent had arsenic, with 8 percent containing it at a level above the Safe Drinking Water Act standard for public water supplies. Wells with high arsenic contamination (greater than or equal to 0.01 mg/L) are marked in red on the above map. The blue marks are wells that had low levels. Click the graphic to read the full study.

Investigators sampled 473 wells in 89 Iowa counties for bacteria, nutrients, metals, common use herbicides and insecticides, and herbicide degradates from May 2006 to December 2008.

Peter Weyer, the study’s lead investigator and associated director for the Center for Health Effects of Environmental Contamination, said that while nitrate and bacteria detections were expected despite efforts to address such contamination, the presence of arsenic was potentially worrisome.

“Nearly half the wells sampled had some level of arsenic, and 8 percent of those had a level that could be considered a health concern,” he noted.

One of the positive findings of the study was that the levels of the commonly used herbicide atrazine appear to be decreasing.

Of the wells tested, 43 percent had total coliform bacteria, 19 percent had enterococci and 11 percent had E. coli. In addition, 49 percent had nitrate, with 12 percent of those having levels above the U.S. Environmental Protection Agency’s standard for public water supplies.

Pesticides parent compounds were found in a small percentage of wells. A total of 8 percent had very low concentrations of atrazine, 2 percent had metolachlor and less than 1 percent of the wells had acetochlor, alachlor and trifluralin.

Herbicide degradates, or the breakdown products of the parent compound that are generally believed to be less toxic, were also found in a percentage of Iowa wells. The degradate most commonly found was metolachlor ethane sulfonic acid (ESA), which was present in 33 percent of the wells. Alachlor ESA was detected in 27 percent of the wells, while desethyl-atrazine and acetochlor ESA was present in 11 percent of the wells tested. In addition, 8 percent of the test wells had metolachlor OXA (oxanilic acid).

“If you do have a problem with your well — certainly bacteria is a problem — and if you had bacteria contamination of your well, you definitely want to boil your water,” said Weyer. “With nitrate, the research on it is kinda mixed on whether it is a problem. We have looked at things like cancer and blue baby syndrome. Some people think that the nitrate standard should be a lot higher, maybe 20 or 25. And there are others who have done research, including myself, who have found problem with nitrate at less than 10, think we ought to leave the standard alone.”

But, by and large, is the drinking water from these wells safe?

“You know, it is hard to say. I think, in general, the well-water quality in the state of Iowa really hasn’t improved that much,” Weyer said. “Compared to the study that was done in 1988 and 1989 the water quality just hasn’t improved very much with respect to nitrate and bacteria. We hadn’t looked for arsenic before, but now we are seeing that. It is really up to the individual well owner as to how they want to deal with this.”

While there was no one major indicator to determine which wells might contain contaminants, there were variables, such as well depth, that were considered by the researchers to be associated with detection. Wells under 100 feet deep had higher concentrations of nitrate and more total coliform bacteria and herbicide degradate detections than deeper wells. Wells that were constructed prior to 1991 had also had more detections. Other factors, including the construction characteristics of the wells and the presence of a liner, also were factors that could impact a well’s vulnerability to contamination.

Wells located in the northwest, southwest and south-central portions of the state were more likely to have detections of total coliform bacteria, E. coli and enterococci. In addition, wells located in the northwest and southwest regions were also more likely to have higher nitrate concentrations.

Perhaps alarmingly, the study is the state’s first systematic sampling of private wells since 1994. Although water quality in public water supplies is monitored and regulated under the Safe Drinking Water Act, private drinking water wells are not monitored under any regulatory framework. In addition, despite an estimated 450,000 Iowans using private wells for drinking water, statewide monitoring has been sporadic during the past two decades, often only following catastrophic events like the 1993 floods.

Because there is so little government monitoring and over-sight of contaminants, one of the best factors to determine the health of well water was monitoring, assessment and treatment by well owners themselves. And while some may point to Iowa’s agricultural industry as a potential culprit in the issue of groundwater contamination, Weyers warns that there are many other potential culprits.

“Agriculture is one of the sources — certainly if you are looking at herbicides and pesticides, and we found some herbicide breakdown products in the well water in this study. That is certainly an agricultural source,” he said. “For things like nitrate and bacteria, not only is nitrogen fertilizer use a problem, but it is also potentially septic systems or municipal wastewater systems. So it is sort of an urban-rural mix as to the source of these contaminants.”

Researchers recommend full use of Grants-to-Counties funds for annual testing of private wells for possible contaminants as well as a consumer education initiative to provide information on the sources of bacteria, factors impacting bacterial contamination of wells, possible health impacts of consumption of such water, and available well treatment options.

Because the tested samples revealed the presence of chloride, which typically is only detected in groundwater near deep saline brine, it was also recommended that the state investigate for possible surface activities (such as de-icing compounds and fertilizer salts) that could be impacting groundwater throughout Iowa.

In the meantime, what should private well owners do?

“We suggest that if you have bacteria or high arsenic [levels] that you don’t drink that water, that you do something to treat the water to effectively remove those contaminants,” Weyer said. “It is something the well owner needs to discuss with their doctor or someone like that to determine if that water is OK for them.”