The issue of whether perchlorate poses a cancer risk is a critical one, and one on which the science has been clear: perchlorate does not cause cancer.
Several national scientific and health organizations have reached this conclusion. Read below to learn more about each organization’s study of perchlorate and cancer.
The National Academy of Sciences
After careful review, the National Academy of Sciences (NAS) panel on perchlorate concluded that perchlorate is unlikely to cause cancer. Earlier studies of rats that had led to speculation about cancer in humans were dismissed by the NAS, which stated it is unlikely perchlorate poses a cancer risk to humans due to the species differences between rats and humans in thyroid function.
It is an accepted medical fact that any effects of perchlorate are limited to the thyroid gland. The U.S. Environmental Protection Agency (EPA) has stated there is no known chemical carcinogenic to the human thyroid. The EPA also acknowledges perchlorate is not mutagenic - that is, it does not cause permanent changes in the genetic material of cells that can be passed on when the cell divides. Genetic changes in the cell are often the precursor of cancerous conditions.
To be cautious, after reviewing data from a 1998 Argus Labs study, "Two Generation Reproduction Study of Ammonium Perchlorate in Rats," EPA stated in its risk assessment that perchlorate "may" pose a cancer risk to humans. The EPA is required to make this assumption based on its own Policy for Assessment of Thyroid Follicular Tumors.
In the Argus Labs study, perchlorate was given in various doses to different groups of pregnant rats. The effects were studied in two generations of those rats' offspring. Out of a total of 60, two offspring in the highest dose group developed adenomas of the thyroid gland. To equal the dose of perchlorate received by the mothers of those rats that experienced health effects, a human would have to drink 20,000 gallons of water containing 20 ppb of perchlorate every day.
The State of California
A peer-reviewed document produced for the University of California stated "no data are presented that show perchlorate, by itself, is a carcinogen." Likewise, California's Office of Environmental Health Hazards Assessment (OEHHA) stated "perchlorate does not pose a known cancer risk to the public." Read more.