FAST FACTS: Issue #8

Study in Chile Confirms NAS Findings

Tellez et al., 2005, “Chronic Environmental Exposure to Perchlorate Through Drinking Water and Thyroid Function During Pregnancy and the Neonatal Period” (Published in the peer-reviewed journal Thyroid, September 2005):

  • This research studied approximately 60 women during pregnancy and post partum in Taltal, a city in northern Chile where the entire municipal drinking water supply contains 110 to 115 parts per billion (ppb) of naturally-occurring perchlorate.
  • This study confirms the National Academy of Sciences perchlorate committee findings “that an RfD of 0.0007 mg/kg per day should protect the health of even the most sensitive populations.” (0.0007 mg/kg per day is roughly 24.5 ppb).
  • The study compared the thyroid function of these women during pregnancy and post partum with that of a similar number of pregnant women in each of two nearby cities: Antofagasta, with non-detectable perchlorate levels; and Chanaral, with 6 ppb perchlorate in the municipal drinking water.
  • Individual maternal perchlorate dose estimates were made based on urine perchlorate concentrations measured at the Centers for Disease Control and Prevention, and 90 percent of the women studied in Taltal were receiving perchlorate doses between 0.0007 and 0.007 mg/kg-day (between the RfD and 10 times the RfD).
  • Neonatal thyroid function at birth also was evaluated via cord blood testing in each of the three cities. There were no maternal or neonatal hypothyroid effects attributable to perchlorate in Taltal relative to the two control cities.

An abstract of Tellez et al., 2005 can be found at:;=pubmed&dopt;=Abstract&list;_uids=16187904&query;_hl=19