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When does nitrate become a risk for humans?

When does nitrate become a risk for humans?
Current limits for nitrate in drinking water may not be justified by science

A few years ago the University of Nebraska Agronomy Department published a paper titled, "When does Nitrate Become a Risk for Humans?" It asked, "Is nitrate harmful to humans?" Also, "Are the current limits for nitrate concentration in drinking water justified by science?"

Well, we know nitrates are a problem. Everywhere we look, EPA and others tell us how terrible nitrates are for the environment.

But, as usual, there are two sides of the story.

Current limits for nitrate in drinking water may not be justified by science

If you believe the Board of Water Works of the City of Des Moines and its complaint against three upstream Iowa county drainage districts, you can only conclude nitrates are a significant health problem for the 500,000 citizens of Des Moines, because their water is polluted by farmers' use of nitrogen fertilizers.

The complaint claims health risks are caused by the farmers' nitrate. One health risk is the creation of "blue baby syndrome," or methaemoglobinaemia. DMWW cites the EPA Safe Drinking Water Act standard of a maximum contaminant level of 10 mg/L, or 10 ppm (1ppm=one inch in 16 miles), and that it is being violated by drainage district discharges.

Related: Des Moines sues Iowa counties over water quality: What does it mean?

DMWW's lawsuit claims the defendant Drainage Districts, in paragraph 139, exceeded the 10 ppm nitrate standard for days in July, September, October and December of 2014. DMWW claims the Drainage Districts are discharging "…unsafe concentrations of nitrate to…the Raccoon River…"

A friend of mine in Texas is a emergency physician and lawyer and constantly reminds me to go to the scientific data. The data are interesting and prove my friend's point.

First, where does the EPA 10 mg/L (10 ppm) standard come from? The University of Nebraska paper produced by 9 individuals, copyrighted by the American Society of Agronomy, Crop Science Society of America and Soil Science Society of America, provides an answer. It concludes the connection between nitrate ingestion and blue baby syndrome is based on studies conducted in the 1940s in the Midwest. The water used in testing on babies was rural well water and was used to make baby formula.

Well water testing

In 1945, Iowa City physician Hunter Comly found the well water he tested contained bacteria as well as nitrate. The wells tested were situated near barn yards and pit privies. Comly also found an absence of blue baby syndrome when the babies' formula milk used tap water rather than well water.

"Re–evaluation of these original studies indicated cases of methaemolglobinaemia (blue baby syndrome) always occurred when wells were contaminated with human or animal excrement and that the well water contained appreciable numbers of bacteria and high concentrations of nitrate."

The Nebraska paper describes another 1948 study where infants were administered doses of 175-700 mg/L of nitrate per day and the study strongly suggested that nitrate alone did not cause the blue baby syndrome. The paper goes on to say a report of the American Public Health Association in 1950 "…formed the main basis of the current recommended…nitrate limit, but even the authors of the report recognized it was compromised by unsatisfactory data and methodological bias."

Related: Water quality on the farm: A three-part Farm Futures exclusive

The paper does set forth the need for caution in evaluating all the scientific data. It discusses the central role that nitrogen and nitrates play in agriculture. The paper concludes by asking, "Is nitrate in drinking water really a threat to health?" The authors write, "If nitrate in drinking water is not a hazard to health, could the current limit be relaxed…"

The scientists believed there are sufficient criticisms to the scientific foundation of the present EPA drinking water standard. They raise a number of questions as to whether the nitrate intake by humans can be raised in drinking water and whether there would be a potential adverse health effect.

The scientists close by saying "…there is an urgent need for a comprehensive, independent study to determine whether the current nitrate limit for drinking water is scientifically justified or whether it could safely be raised." Based on a review of the DMWW complaint it appears the trustees believe they know the Clean Water Act law and the science of nitrates. The Nebraska paper published in the Journal of Environmental Quality suggests otherwise.

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