Food safety assessment of perchlorate contaminated crops in rodents

Perchlorate contamination in the environment has raised considerable concern in recent years. Contaminated water may be used for drinking or irrigation of crops intended for use by humans and livestock. Plants may accumulate perchlorate at higher concentrations than that of the surrounding soil and water, suggesting an additional source of exposure. Perchlorate interferes with the production of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), by competing with iodide for uptake into the thyroid gland. Due to the solubility of perchlorate, previous small mammal studies have used water as the dosing vehicle. To date, there is no published research on the potential effects of perchlorate contaminated food. We conducted a two-generation study comparing the effects of perchlorate in deer mice exposed via contaminated food to those exposed via water. Perchlorate contaminated soybean plants iGlycine tnax) were incorporated into rodent diet and fed to mice ad libidum. The second group was exposed to perchlorate in water at a concentration slightly less than that of the food-exposed group. There were no significantly different histopathological measurements behween groups. Analysis of thyroid glands for T4 content showed no significant differences between treatments. After 21 days, males in the perchlorate-contaminated food (PCF) treatment had decreased T3 concentrations compared to controls. At day 44, males in the PCF treatment had elevated concentrations of T4 compared to controls. Animals in the perchloratecontaminated water (PCW) treatment following gestational, lactational, and postlactational exposure had elevated T3 concentrations compared to controls. Although not significantly different, reproductive success, number of uterine placental scars and survival of offspring was lower in the PCF and PCW compared to Controls. These data suggest that at environmentally relevant concentrations, perchlorate may be reproductive and developmental toxicant to deer mice.