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Perchlorate - a chemical compound suspected of adverse health and ecological effects - has been identified in some fertilizers used by homeowners and farmers, according to a study by scientists affiliated with the United States Environmental Protection Agency's National Exposure Research Laboratory in Athens, Ga.
"These preliminary results suggest that fertilizers could be a source for perchlorate accumulation in the food chain," states the study, which will appear in the Oct. 1 print edition of the scientific journal Environmental Science & Technology, published by the American Chemical Society, the world's largest scientific society. The article was published Aug. 13 on the journal's web site. Perchlorate occurs naturally in several fertilizer components, rocks and minerals used in the manufacturing process, the article states.
"Perchlorate is of concern because of uncertainties about toxicity and health effects at low levels in drinking water, impact on ecosystems and indirect exposure pathways for humans due to accumulation in vegetables," according to the article. Perchlorate's potential to disrupt thyroid function raises concerns about thyroid cancer and its effects on the developing nervous system.
The new study lends support to other reports of perchlorate in fertilizers. EPA continues to assess perchlorate's toxicity and associated health risks in partnership with other government agencies.
Nine brands of fertilizer purchased at local stores in the Athens, Ga., area were analyzed as part of the study. They contained levels of perchlorate ranging from 0.15 percent to 0.84 percent by weight.
"Use of three independent analytical methods (spectroscopic, chromatographic and electrophoretic) firmly establishes that perchlorate is in some but not all commercial fertilizers," says EPA's Steve McCutcheon, Ph.D., one of the authors of the study. He adds, "The source and extent of perchlorate is a true mystery at the moment."
Research is ongoing to determine the magnitude of perchlorate contamination in fertilizers, and to determine how much perchlorate may be retained by leafy vegetables such as lettuce.
Used in solid rocket fuel, fireworks and matches, perchlorate has previously been implicated in the contamination of groundwater, surface water and soils, particularly in the southwestern United States. The compound is mobile in surface water and groundwater, where it can persist for several decades, the study notes.
There is no national standard for perchlorate in drinking water, but monitoring programs are likely to expand as analytical methods are standardized.
The study concludes with a call for more research: "Clearly, improved knowledge of the potential human exposure to perchlorate through the fertilizer-food chain pathway is warranted based on the results of this screening study."
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