High Levels of TSH in Arizona Newborns

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Sep 29, 2000

In a study published in the August 2000 issue of the Journal of Occupational and Environmental Medicine (JOEM), researchers looked at the TSH (thyroid stimulating hormone) levels of newborns in two Arizona cities. They compared 1099 newborns from Yuma on the Colorado River where the water supply contains ammonium perchlorate to 443 newborns in Flagstaff where the water supply does not contain perchlorate. They found that newborns in Yuma had higher levels of TSH suggesting suppression of thyroid function. They identified that the newborns have higher levels of TSH but don't know if these newborns will develop thyroid disease.

Perchlorate suppresses thyroid function by inhibiting the uptake of iodine as animal studies have shown. It is used in the production of rocket fuels and has been discarded in Nevada since the 1950s. As early as 1997, water in the Colorado river was known to contain perchlorate. In an article published August 19, 1997 in the Las Vegas Review-Journal, Keith Rogers reported that water in Lake Mead on the Lower Colorado River system contained concentration 100 times higher than the level considered safe for drinking. The water in the Lower Colorado River system supplies cities in Nevada, Arizona and California affecting millions of people.

Rocket fuel may not be the only source of perchlorate contamination. In March 1999 the EPA identified perchlorate in eight fertilizer samples. The Fertilizer Institute on the Q&A page referenced states that it believes that its products are safe but acknowledges that "current data do not support definitive conclusions regarding perchlorate presence in fertilizer."

An earlier study published in the June 2000 issue of JOEM, studied 162 school age and 9784 newborns in 3 cities of northern Chile where the levels of perchlorate in the drinking water ranged from 100-120 mcg per liter in Taltal to undetectable in the control city of Antofagasta. The study concluded that the findings did not show suppression of thyroid function at 100-120 mcg/L. The EPA, through the National Center for Environmental Assessment, is conducting ongoing studies to further study the effects of perchlorate on the thyroid.