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Thursday August 10 10:34 AM ET Chemical in Water May Cause Thyroid Troubles

NEW YORK (Reuters Health) - Drinking water contaminated with low levels of perchlorate--a chemical used in the production of rockets, missiles, fireworks and matches--may be to blame for unusual thyroid hormone levels in some Arizona newborns, results of a study suggest.

The chemical has made its way from disposal sites in Nevada into the Colorado River system, which is a source of drinking water for about 20 million people in Arizona, California and Nevada, according to a team of researchers led by Dr. Ross. J. Brechner, of the Arizona Department of Health Services in Phoenix.

The amount of perchlorate that humans can consume without experiencing any ill effects is uncertain. Ordinary water-treatment plants cannot remove the chemical from the water supply.

The chemical is known to affect the function of the thyroid gland, so Brechner's team decided to compare cases of thyroid problems in children born in two Arizona cities--Yuma, where the water supply contains perchlorate, and Flagstaff, where the water is perchlorate-free.

Compared with infants born in Flagstaff, those born in Yuma had high levels of hormones that stimulate the thyroid, which may indicate that the thyroid is not functioning properly, Brechner and colleagues report in the August issue of the Journal of Occupational and Environmental Medicine.

The levels were still elevated even when the researchers took into account factors that might have affected thyroid-stimulating hormones, such as race, ethnicity and age at testing.

If not detected and treated promptly, thyroid problems may affect a child's mental development, according to the report.

``We're not telling people to stop drinking the water,'' Brechner told Reuters Health in an interview. There is not enough evidence to prove that perchlorate in the water causes thyroid problems, he said.

``There is a statistical association between low-level contamination with ammonium perchlorate and elevated or abnormal thyroid function,'' Brechner said. ``We do not know the clinical significance of this.''

He and his colleagues conclude that further research is needed to measure levels of the chemical in the water supply and to confirm whether it might cause health problems.

SOURCE: Journal of Occupational and Environmental Medicine 2000;42:777-

-- K (infosurf@yahoo.com), August 10, 2000