October 13 (HealthDay News) -- Exposure to perchlorate, a chemical used in rocket fuel, explosives, road flares, and pyrotechnics, may lower thyroid function in women, particularly those with low iodine intake, according to a study from the U.S. Centers for Disease Control and Prevention (CDC).

Men's thyroid function was not affected by perchlorate exposure, according to the study of nearly 2,300 people age 12 and older. The findings were published in the journal Environmental Health Perspectives.

Large amounts of perchlorate have been shown to inhibit iodine uptake and reduce thyroid hormone function. Prolonged reduction in thyroid hormone can cause metabolic problems in adults and abnormal neurodevelopment during gestation and infancy.

Perchlorate is widespread in groundwater, drinking water, and foods including milk, vegetables, fruit, grain, and forage crops in the United States.

The CDC researchers analyzed blood and urine samples from the participants and found that perchlorate was a significant predictor of thyroid hormone levels in females, but not in males.

The scientists then focused on the 1,000 females in the study and found a slight relationship between perchlorate exposure and thyroid hormone levels in women with higher urinary iodine levels, but a much stronger association in women with lower urinary iodine levels (less than 100 micrograms iodine per liter of urine).

About 36 percent of U.S. women have low urinary iodine levels.

The CDC scientists said the findings of this study need to be confirmed in another large study. They're currently planning that follow-up study.

SOURCE: Environmental Health Perspectives, news release, Oct. 4, 2006