Nitrates in the water may be more harmful than we thought

Elevated nitrates in drinking water — a persistent problem in Iowa — have been be linked to health concerns that include birth defects, cancers and thyroid problems, according to a state environmental group's review of dozens of health studies.

The studies reinforce the need for Iowa to work harder to reduce nitrates and other pollution in the state's rivers and streams, the Iowa Environmental Council said.

Iowans “are particularly vulnerable to the potential health impacts from nitrate pollution," according to the group's report, released Thursday.

“Concentrations of nitrate in Iowa’s streams and groundwater have been found to rank among the highest in the U.S., even higher than elsewhere in the Corn Belt and Northern Great Plains,” said the group, which emphasized the need to learn more about nitrates' health impacts.

The Des Moines Register reported last year that state environmental data showed more than 60 Iowa cities and towns had battled high nitrate levels in their drinking water the past five years.

The state said the water supplies of about 260 cities and towns were highly susceptible of becoming contaminated by nitrates and pollutants — about 30 percent of Iowa's 880 municipal water systems. The state data provide a snapshot of the cities reporting nitrate levels of 5 milligrams per liter or higher, a warning sign that nitrates are approaching harmful levels.

The Iowa Environmental Council said most health concerns associated with high nitrate levels in drinking water have centered on blue baby syndrome, a condition that can be fatal to infants 6 months and younger if not treated.

But federal drinking water standards, which require nitrate levels to be below 10 milligrams per liter, have made deaths from blue baby syndrome rare and prompted some state leaders to question whether acceptable nitrate levels should be raised, the group said.

Several Iowa, U.S. and global studies have associated nitrate levels in water with more far-reaching health problems, the report states.

"While most of the associations have been found when nitrate levels are higher than the drinking water standard," the Iowa Environmental Council said, "some research suggests that nitrate concentrations even lower than the drinking water standard may be harmful."

Peter Weyer, interim director of the Center for Health Effects of Environmental Contamination at the University of Iowa, has looked the impact of long-term exposure to low levels of nitrates. His work shows an association between nitrates and some cancers in women.

"Based on our research and elsewhere in the U.S. and abroad, it looks like nitrates are problematic for other health effects," said Weyer, who reviewed the group's report. "It's important to realize there are other reasons to be concerned about high nitrate levels in drinking water."

State says drinking water is safe

The Iowa Department of Public Health, calling the group's water quality and health overview "objective," agreed that the science around water quality and chronic illness is evolving.

"While Iowans should not be overly alarmed as far as immediate health risks, it is important to have Iowans engaged in debating and understanding the impacts of water quality on our state," the agency said, noting that acute illnesses from drinking water in Iowa are rare.

The department said Iowa's last case of blue baby syndrome was in the 1970s.

"The ongoing surveillance of our water and further scientific review of health effects will be important in understanding the long term health impacts," the agency said.

Jon Tack, chief of the Iowa Department of Natural Resources’s water quality bureau, said the agency will review the report and its recommendations.

"Raising public awareness beyond the impact of blue baby syndrome is positive,” Tack said, adding that the agency has received no requests to raise the standard for nitrate levels.

Tack echoed the Public Health department’s assurance that the state’s drinking water is safe for residents. The drinking water standards are set by the U.S. Environmental Protection Agency under the Safe Drinking Water Act.

Rising concerns about nitrates

Nitrates have become a greater concern in Iowa after Des Moines Water Works filed a lawsuit last year against drainage districts in three northern Iowa counties, claiming that underground drainage tiles in farm fields act as conduits that funnel high levels of nitrates into the Raccoon River, a source of drinking water for 500,000 central Iowa residents.

The utility spent $1.5 million last year to remove nitrates to levels that were safe for consumers. Water Works seeks federal oversight of the Iowa drainage districts, and indirectly, farmers.

The Iowa Environmental Council, along with conservation and farm groups, support creating a long-term funding source to scale up the Iowa Nutrient Reduction Strategy, the state's plan to cut by 45 percent the nitrogen and phosphorus levels that enter Iowa waterways and contribute to the Gulf of Mexico dead zone.

The council supports levying an additional three-eighths of 1 cent sales tax to fund the Natural Resources and Outdoor Recreation Trust Fund, which was created through a constitutional amendment. Sixty-three percent of Iowa voters supported the fund in 2010 to improve Iowa's water, soils, fish and wildlife habitat, parks and trails, but the Legislature has never approved money for it.

The report said Iowa's nitrate problems create a "significant challenge for public drinking water suppliers" that must meet federal standards. "In addition, many Iowans rely on private wells that are unregulated and often untested.

The Register reported last month that 15 percent of private wells voluntarily tested between 2006 to 2015 had nitrate levels that exceeded federal standards, according to Iowa Department of Public Health data.

“These Iowans are at a greater risk of ingesting elevated concentrations of nitrate or other regulated pollutants,” the Iowa Environmental Council said.

Determining the proper standard

Nitrate pollution comes from urban and rural sources that include fertilizers used on crop fields and lawns, leaking septic tanks, wastewater treatment systems, livestock manure and soil tillage.

The environmental council noted that last year, "11 public water supplies — including municipalities, rural water districts, churches, residential care facilities and mobile home parks — exceeded federal safe drinking limits for nitrate or nitrite during 2015," based on a state drinking water compliance report.

Overall, 94.5 percent of Iowa's nearly 1,900 regulated public water supplies met Iowa's health-based drinking water standards, the state said.

In addition to drinking water, people are exposed to nitrates from multiple sources: Some vegetables, processed meats, cigarette smoke and a variety of drugs that contain “nitrosatable,” or nitrogen-based compounds, the group said. 

Weyer, the University of Iowa environmental health director, said health concerns support the U.S. Environmental Protection Agency keeping nitrate maximum contaminant levels where they are.

"Based on what researchers are seeing with cancer and birth defects, we should at least leave the standard where it is," he said. "We need to more research before we do anything."

Nitrate health concerns

Here's a roundup of the health concerns the group identified in reviewing up to 200 health studies:

• Birth defects: Studies conducted in Iowa, Texas, Canada and Australia found statistically significant links between elevated nitrate in drinking water and neural tube defects of the brain and spinal cord, including spina bifida, some oral cleft defects and limb deficiencies.
• Bladder cancer: Researchers who followed a large group of post-menopausal women in Iowa over many years found an increased risk for bladder cancer as nitrate concentration in water supplies increased. Other likely influences, including exposure to nitrate and nitrite through dietary and other sources, also were considered. Studies in Spain, Germany and Taiwan reported similar findings.
• Thyroid cancer: One of the most rapidly increasing cancers in the United States, thyroid cancer, also has been associated with extended exposure to high nitrate levels in drinking water in two large U.S. studies.