Nitrate effects in drinking water may be worse than thought: report
Possible link found to birth defects, thyroid cancer
Health risks associated with nitrate in drinking water may go beyond blue-baby syndrome, according to a report released Thursday by the Iowa Environmental Council.
Multiple studies have found links between nitrate in drinking water and birth defects, thyroid cancer and bladder cancer, said lead author Ann Robinson, who reviewed more than 100 such studies and consulted with numerous health experts.
“Human health needs to be a larger part of the conversation about Iowa’s water quality,” she said, which has centered primarily on the effects of elevated nitrate levels on the natural environment.
Among the cited studies was one that found that prenatal nitrate intake in the mother’s drinking water was “significantly positively associated” with offspring diagnosed with spina bifida, oral cleft defects and limb deficiencies.
A 2001 Iowa Women’s Health Study found an increased risk for bladder and thyroid cancer as nitrate concentration in water supplies increased.
“We did find an association, but not a causal relationship, between those cancers and nitrate in drinking water,” said Peter Weyer, director of the University of Iowa Center for Health Effects of Environmental Contamination.
The study, which had a significantly large sample, found that women exposed for 10 or more years — even to water testing below the 10-parts-per-million safe drinking standard — had as much as twice the risk of contracting those cancers as women not exposed to nitrates in their drinking water.
Robinson, the council’s agricultural policy specialist, said the study was prompted by a recent surge of comments that the Environmental Protection Agency’s drinking water standard may be too stringent.
“We were hearing a lot of people asking, ‘When’s the last time you saw a blue baby?’” she said.
Since the 1960s, elevated levels of nitrate in water used for baby formula have been known to pose the risk of methemoglobinemia, or blue-baby syndrome — a serious, potentially fatal condition that decreases the blood’s ability to carry vital oxygen through the body.
In 2014, the Iowa Department of Public Health database recorded two cases of methemoglobinemia, neither of which involved an infant.
“It’s hard to prove a direct causal link between nitrates and other ailments, but health research is all about identifying increased risks,” Robinson said.
An estimated 288,000 Iowans — about nine percent of the state’s population — drink from private wells, which are not regulated and are often untested, according to Russell Tell, a senior environmental specialist with the Department of Natural Resources.
A landmark survey of rural wells conducted from 2006 to 2008 found that 49 percent of the 473 wells sampled had nitrate, with 12 percent exceeding the safe drinking water standard.
The research reviewed in the study helps define the health risks associated with nitrate-polluted drinking water and is useful for Iowans in making informed decisions to address them, said Jeneane Moody, executive director of the Iowa Public Health Association and a reviewer of the report.
The findings offer compelling reasons to accelerate efforts to reduce pollution from nitrate flowing into surface and ground water, Robinson said.
Elevated nitrate levels in Iowa’s drinking and recreational waters have been a concern since the state was identified in the 1990s as a top contributor of the nitrate and phosphorus pollution that fuels the Dead Zone in the Gulf of Mexico.
The issue has received increased attention following the Des Moines Water Works lawsuit against three drainage districts in Northwest Iowa, an area identified as a hot spot for nitrate pollution.
Robinson said the Iowa Environmental Council considers the state’s nutrient reduction strategy a “toolbox” that offers sound, science-based measures for curbing nutrient pollution. The council also urges establishment of a sustainable source of funding with clear timelines and accountability measures to support nutrient reduction efforts, she said.