Ammonium perchlorate contamination of Colorado River drinking water is associated with abnormal thyroid function in newborns in Arizona

The Colorado River below Lake Mead, which supplies drinking water for appro ximately 20,000,000 people, is contaminated by ammonium perchlorate. We ide ntified populations who were exposed and unexposed to perchlorate-contamina ted drinking water and compared median newborn thyroid-stimulating hormone (TSH) levels after adjusting for age in days at measurement and for race/et hnicity, Median newborn TSH levels in a city whose drinking water supply wa s 100% perchlorate-contaminated water from the Colorado River below Lake Me ad were significantly higher than those in a city totally supplied with non perchlorate-contaminated drinking water, even after adjusting for factors k nown or suspected to elevate newborn TSH levels. This ecological study demo nstrates a statistically significant association between, perchlorate expos ure and newborn TSH levels. It suggests that even low-level perchlorate con tamination of drinking water may be associated with adverse health effects in neonates and highlights the need for both further study and control of h uman low-level perchlorate exposure.