The History of Perchlorate: Evolving Science, Technologies and Regulations

1950s Military begins using perchlorate as ingredient in solid rocket fuel. Medical community begins using perchlorate at very high levels (equal to 70,000 to 300,000 parts per billion in drinking water) to treat hyperthyroidism.
1992 U.S. Environmental Protection Agency (U.S. EPA) proposes "provisional" Reference Dose (safe exposure level) for perchlorate of 4 parts per billion (ppb) in drinking water.
1993 Aerospace, defense and chemical companies form Perchlorate Study Group and join with government agencies to fund studies on health effects of perchlorate.
1994 Full-scale development of perchlorate removal and treatment technology gets under way.
1995 U.S. EPA raises "provisional" Reference Dose to 4-18 ppb.
1997 In California, monitoring technology is developed enabling perchlorate detection at levels as low as 4 ppb. California Department of Health Services (DHS) sets "provisional" Action Level (level at which water companies or districts must report presence of perchlorate) at 18 ppb.
1998 Based on results of eight new studies on humans and animals, U.S. EPA proposes "draft" Reference Dose of 32 ppb.
1999 U.S. EPA peer review panel concludes a "draft" Reference Dose of 32 ppb level is probably overly cautious and recommends additional study.
2000 New studies show humans - even sensitive sub-populations - can consume perchlorate at levels up to 200 ppb in drinking water with no risk of adverse health effects.
January 2002 U.S. EPA relies primarily on animal studies, particularly a scientifically flawed and controversial rat study, to propose new "draft" Reference Dose of 1 ppb.
February 2002 In response to U.S. EPA's "draft" Reference Dose, California Department of Health Services lowers "provisional" Action Level from 18 ppb to 4 ppb.
December 2002 California proposes "draft" Public Health Goal of 2 ppb for children and 6 ppb for adults in drinking water. (Controversy around this decision leads California to call for a peer review by a panel of scientists convened by the University of California.)
April 2003 U.S. EPA puts "draft" Reference Dose of 1 ppb on hold until completion of peer review by the National Academy of Sciences.
June 2003 California puts Public Health Goal on hold pending completion of peer review by scientists acting under auspices of University of California (UC).
January 2004 UC peer reviewers submit three separate reports regarding the risk assessment used to develop California's draft Public Health Goal. All three disagreed with California, and one another, on what the science says and how the state should proceed.
March 2004 California issues perchlorate Public Health Goal of 6 ppb in drinking water. This accounted for exposure to perchlorate in water, farm products and cow's milk. However, the state will carefully review the conclusions reached by the National Academy of Sciences and revise the Public Health Goal as necessary.
March 2004 California, in issuing its Public Health Goal for perchlorate, states that .
May 2004 Massachusetts Department of Environmental Protection establishes a draft toxicity value for perchlorate at 1 ppb.
January 2005 National Academy of Sciences releases its report "Health Implications of Perchlorate Ingestion," which recommends a reference dose of perchlorate at 0.0007 milligrams per kilogram per day.
February 2005 U.S. EPA establishes its official reference dose of perchlorate at 0.0007 milligrams per kilogram per day and translated that number to a Drinking Water Equivalent Level of 24.5 ppb.