California women exposed to rocket fuel chemical perchlorate

Many California women who have been exposed to the chemical perchlorate -- a rocket fuel component that has contaminated 450 wells and other water sources in the state -- have suppressed thyroid function, according to a CDC study published on Wednesday in the journal Environmental Health Perspectives, the Los Angeles Times reports.

Benjamin Blount of the CDC's National Center for Environmental Health and colleagues analyzed thyroid hormones and perchlorate levels of 1,111 women living in the state to determine if there is a relationship between the two.

The study finds that, on average, women were ingesting 2.9 parts per billion of perchlorate -- 10 times less than the amount the Environmental Protection Agency considers safe.

Women who were exposed to moderate or high levels of perchlorate had 8% to 33% less thyroxine -- a thyroid regulating hormone also known as T4 -- than the normal range, the study finds.

According to the Times, sustained reductions in thyroid hormones can lead to hypothyroidism in adults and abnormal brain development in fetuses and infants.

The study also finds that the most significant reductions in the level of thyroid hormones were seen in women with iodine levels of less than 100 micrograms per liter, the minimum level the World Health Organization recommends.

No reduction in the level of thyroid hormones was seen in men, according to the study.

"For women overall, perchlorate was a significant predictor" of the levels of T4 and a thyroid-stimulating hormone, called TSH, according to the study.

In a report accompanying the study, EHP said that the reduction in thyroid hormones is "significant" and that it "indicate[s] that even small increases in perchlorate exposure may inhibit the thyroid's ability to absorb iodine."

According to the Times, California in August proposed its own drinking water standard of six parts perchlorate per billion.

The state health agency is scheduled to conduct a hearing on the proposal on Oct. 30 in Sacramento, Calif., and public comment will be accepted until Nov. 3 (Cone, Los Angeles Times, 10/5).