A concern that perchlorate would make its way into the human food chain through vegetables such as broccoli, cauliflower and lettuce has been the stimulus for research by University of Arizona Research Scientist Charles Sanchez, director of the Yuma Agricultural Center, part of the College of Agriculture and Life Sciences at the University of Arizona in Tucson.
Perchlorate is one of the main ingredients of solid rocket propellant. Improper disposal of perchlorate-containing chemicals may result in contaminated soil and water. Because it can affect humans by inhibiting the thyroid's uptake of iodine, Sanchez has been evaluating the extent to which perchlorate is found in desert food crops irrigated with Colorado River water. Perchlorate levels in water have been as high as 14 parts per billion, detected at Lake Mead, the reservoir behind Hoover Dam.
"What I measure in water at the Imperial Diversion Dam near Yuma ranges from two to seven parts per billion," Sanchez says. The lower concentrations may be due to biological factors, such as uptake by aquatic and riparian plant species along the river, and perhaps microbial reduction. It appears that microbial organisms capable of reducing perchlorate to chloride are fairly widespread, however conditions that favor this reaction rarely exist in nature.
A preliminary survey conducted in 2002-2003 generally found perchlorate concentrations near or below detection for most vegetable crop species sampled, including most vegetables eaten as roots and fruits. The exception was leafy vegetables, such as lettuce, where the foliage is consumed. However, f
Contact: Charles Sanchez
University of Arizona