Estimates of exposures to perchlorate from consumption of human milk, dairy milk, and water, and comparison to current reference dose.

To develop an enforceable drinking water standard from a health-based reference dose, sources of exposure and relevant exposure factors across the U.S. population must be considered. Human exposures, expressed as an estimated daily exposure, can be used to evaluate the health protectiveness of a range of potential regulatory values, thus providing a scientific foundation on which decisions can be based. Recent evidence points to detectable levels of perchlorate in milk and other foods. The purpose of this article is to estimate human exposure to perchlorate from ingestion of drinking water, human milk, and dairy milk. Drinking-water exposure was based on a range of possible regulatory values, derived from the recently established reference dose. Exposure to perchlorate from the consumption of milk was based on exploratory Food and Drug Administration dairy milk data, and on additional published perchlorate concentrations in dairy and human milk samples. This effort is exploratory in nature due to the limited data available at this time. However, it is anticipated that these exposure estimates and comparison with the current reference dose will stimulate dialogue and research that will advance the risk assessment for perchlorate.

Risk assessment, remedial decisions and the challenge to protect public health: the perchlorate case study.

While scientists have a responsibility to defer judgment in the absence of conclusive data, public health and ecological protection require that government regulators make decisions based on available information. The risk assessment paradigm has evolved to help risk managers balance risks to public health with the cost of pollution control and remediation. Risk assessments are designed to be reasonably protective of public health, however the time and money required to develop and evaluate a robust scientific database can significantly delay regulatory action while exposures continue. The federal assessment of perchlorate, a component of rocket fuel and a thyroid toxicant, is presented here as a case study that demonstrates some of the limitations of risk assessment in protecting public health. Perchlorate was detected in a city well field that lies beneath a military training range at Aberdeen Proving Ground, a U.S. Army garrison in Maryland. Cleanup was put on hold, pending promulgation of a national drinking water standard for perchlorate. This case study (1) illustrates the challenge of preventing chemical exposures in the absence of promulgated standards, and (2) makes recommendations for approaches to preventing exposures to chemicals of unknown, or uncertain toxicity before they occur.