FAST FACTS: Issue #5

Perchlorate Does Not Cause Cancer and Does Not Cause Birth Defects

During the past decade, millions of dollars have been spent studying the possible health risks of perchlorate because of its presence at trace levels in some water supplies. Credible scientific and medical research shows that the low levels of perchlorate being detected in drinking water have no measurable effect on pregnant women or fetuses. Furthermore, scientifically credible organizations have stated that perchlorate does not cause cancer in humans.

  • A study by Tellez et al. found no impacts from perchlorate on pregnant women during the critical period between the late first and early second trimesters, and no effect on fetal development or thyroid levels in newborns. The study examined pregnant women and babies from three cities in Chile, where perchlorate levels range from non-detect to 110 parts per billion, and daily intake of dietary iodide is even greater than that in the U.S. This study will be published in the September 2005 issue of Thyroid.
  • The American Thyroid Association issued a press release on October 1, 2004, stating that various levels of perchlorate exposure were found not to be harmful to newborns, pregnant women and other adults.
  • In March 2004, California’s Office of Environmental Health Hazard Assessment issued a “Frequently Asked Questions” document, stating clearly “perchlorate does not pose a known cancer risk.” That document can be viewed at: (see question #12)
  • A study by Kelsh et al. evaluated whether newborns had higher rates of primary congenital hypothyroidism (PCH) or elevated concentrations of thyroid-stimulating hormone in a community where perchlorate was detected in groundwater wells. According to the October 2003 issue of the Journal of Occupational and Environmental Medicine, they found that residence in a community with potential perchlorate exposure has not impacted PCH rates or newborn thyroid function. The abstract can be viewed at:;=PubMed&list;_uids=14534454&dopt;=Abstract
  • The U.S. Environmental Protection Agency has stated “to date, no chemical has been identified as being carcinogenic to the human thyroid.” (See U.S. EPA Policy for Assessment of Thyroid Follicular Cell Tumors, March 1998).