Industry sources doubt there’s a connection between fertilizer and nitrates in drinking water, which have been linked in health studies with a higher incidence of thyroid cancer in older women and underperforming thyroids in infants.
According to The Fertilizer Institute (TFI), its own product testing program has demonstrated that fertilizers are safe. “These studies were reviewed and approved by both the U.S. Environmental Protection Agency (EPA) and the Organization for Economic Cooperation and Development (OECD), and are solid evidence that there is no connection between fertilizers and increased risk of thyroid disease,” stated TFI spokeswoman Kathy Mathers. “It should also be noted that perchlorate and thiocyanate, the other chemicals in the studies, bind the receptor much more strongly, thus are more potent than nitrates.”
In the National Institute of Health (NIH) study of nearly 22,000 women in Iowa ages 55 to 69, researchers found a nearly three-fold increase of thyroid cancer in women who for more than 10 years had used public water supplies with nitrate levels of 5 milligrams per liter – or less than half the maximum allowable level of nitrates in the U.S. According to the report, cancer incidence was determined by using the state health registry, and nitrate intake was estimated from public drinking water sources using a public database of nitrate measurements.
“These positive findings are of interest in light of the increasing incidence of thyroid cancer over the past decades, and the ubiquitous exposure to nitrate from dietary and drinking water sources – the latter occurring mostly in agricultural regions,” the NIH researchers noted.
The other study included 92 full-term infants between birth and 1 year of age. Perchlorate, thiocyanate, and nitrate were measured in 206 urine samples. The thyroid stimulating hormone (TSH) and thyroxine were measured in urines and in 50 blood samples. Infants with higher exposures to three contaminants – perchlorate, nitrate, or thiocyanate – found in water, food, and tobacco smoke, had increased levels of TSH, which researchers say is a sign that the thyroid gland may be underfunctioning.
NIH’s Iowa study of thyroid diseases focused on an agriculture state where nitrate is common in drinking water because of heavy nitrogen fertilizer applications in cornfields. This situation led Des Moines waterworks (DMWW) to build the largest nitrate removal facility in the world. DMWW recently took the additional step to assure the effectiveness of the nitrate-removal plant by diverting Raccoon River water into off-river storage reservoirs, where it’s held long enough for microorganisms to consume nitrate present in the river water. DMWW officials pointed out that nitrate levels rapidly diminish in the storage reservoirs, enabling DMWW to use the water as low-nitrate diluted, which is then mixed with DMWW’s other high-nitrate water sources. These efforts recently earned an environmental excellence award from Iowa Gov. Chet Culver.