Does perchlorate in drinking water affect thyroid function in newborns or school-age children?

Perchlorate is known to suppress thyroid function by inhibiting uptake of i odide by the human thyroid at doses of 200 mg/day or greater. A study was c onducted to investigate the potential effects of perchlorate in drinking wa ter on thyroid function in newborns and school-age children. A total of 162 school-age children and 9784 newborns were studied in three proximate citi es in northern Chile that have different concentrations of perchlorate in d rinking water: Taltal (100 to 120 mu g/L), Chanaral (5 to 7 mu g/L), and An tofagasta (non-detectable: <4 mu g/L). Among schoolchildren, no difference was found in thyroid-stimulating hormone levels or goiter prevalence among lifelong residents of Taltal or Chanaral compared with those of Antofagasta , after adjusting for age, sex, and urinary iodine. No presumptive cases of congenital hypothyroidism were detected in Taltal or Chanaral; seven cases were detected in Antofagasta. Neonatal thyroid-stimulating hormone levels were significantly lower in Taltal compared with Antofagasta; this is oppos ite to the known pharmacological effect of perchlorate, and the magnitude o f difference did not seem to be clinically significant. These findings do n ot support the hypothesis that perchlorate in drinking water at concentrati ons as high as 100 to 120 mu g/L suppresses thyroid function in newborns or school-age children.