Scientific Peer Review
2003 Perchlorate State-of-the-Science Symposium
Regulatory Checkbook designed and assisted in the organization and implemented of a scientific peer review for perchlorate (ClO4-), an anion found in salts containing ammonium, potassium, sodium, and lithium. Ammonium perchlorate is a critical national defense material used as the oxidizer for solid rocket fuel motors and as a propellant in various weapons systems.
The Environmental Protection Agency performed a screening-level risk assessment in 1992, and draft toxicological assessments in 1998 and 2002. As required by the method design, the 1992 screening level assessment was highly precautionary and intended only to identify exposures below which there should be no concern about human health risk. That dose was determined to be 0.00014 mg/kg-day after applying a composite uncertainty factor of 1,000. Using standard factors (2 liters/day of drinking water, 70 kg body weight) that overstate average exposure, thus injecting additional precaution beyond that 1,000-fold uncertainty factor, the drinking water equivalent level was 4 parts per billion (ppb). Properly interpreted, this was intended to be the amount of daily exposure in drinking water that was virtually assured to pose no human health risk. It said nothing about whether exposures above 4 ppb posed any risk, so a comprehensive risk assessment was needed.
In 1998, EPA published a draft risk assessment which proposed to set a Reference Dose at 0.0009 mg/kg-day—about 10-fold greater--equivalent to 32 parts per billion (ppb) in drinking water. The peer review panel judged this to be an improvement but also likely to be highly precautionary. The panel recommended that additional specific, targeted research be conducted.
A public-private partnership was established including EPA, the Department of Defense, NASA, the manufacturer of ammonium perchlorate used by DoD and NASA, and several defense contractors that used ammonium perchlorate in the production of missiles and weapons systems for the government. The private firms, DoD, and NASA would pay for the research recommended by the peer review panel, and EPA would control the research protocols and select the contractors. The partnership was established in response to a recommendation of then Vice President Gore's National Performance Review as a way to reduce red tape and overcome the adversarial relationship typically present between EPA and its regulated parties (see "EPA 10" in National Performance Review 1993, From Red Tape to Results, Appendix A: Major Recommendations by Agency).
This partnership became acrimonious after EPA published its second draft risk assessment in 1992. EPA scientists interpreted the new science to mean that perchlorate was much more risky than they previously had thought; defense and industry scientists interpreted the new science to mean it was less risky. In early 2003, EPA published an interim risk management policy that relied on EPA's interpretation even though the 2002 draft risk assessment remained highly controversial and had not been finalized. This risk management document exacerbated the conflict, which EPA attempted to ameliorate by publishing a Q&A document. The 2003 Perchlorate State-of-the-Science Symposium was an effort sponsored by the defense and industry partners to independently review the new research. EPA was invited but declined to participate. Each of the papers resulting from the Symposium is reprinted in the adjacent tabs. A National Research Council committee relied on these papers extensively in its subsequent review and 2005 report.
The Environmental Protection Agency performed a screening-level risk assessment in 1992, and draft toxicological assessments in 1998 and 2002. As required by the method design, the 1992 screening level assessment was highly precautionary and intended only to identify exposures below which there should be no concern about human health risk. That dose was determined to be 0.00014 mg/kg-day after applying a composite uncertainty factor of 1,000. Using standard factors (2 liters/day of drinking water, 70 kg body weight) that overstate average exposure, thus injecting additional precaution beyond that 1,000-fold uncertainty factor, the drinking water equivalent level was 4 parts per billion (ppb). Properly interpreted, this was intended to be the amount of daily exposure in drinking water that was virtually assured to pose no human health risk. It said nothing about whether exposures above 4 ppb posed any risk, so a comprehensive risk assessment was needed.
In 1998, EPA published a draft risk assessment which proposed to set a Reference Dose at 0.0009 mg/kg-day—about 10-fold greater--equivalent to 32 parts per billion (ppb) in drinking water. The peer review panel judged this to be an improvement but also likely to be highly precautionary. The panel recommended that additional specific, targeted research be conducted.
A public-private partnership was established including EPA, the Department of Defense, NASA, the manufacturer of ammonium perchlorate used by DoD and NASA, and several defense contractors that used ammonium perchlorate in the production of missiles and weapons systems for the government. The private firms, DoD, and NASA would pay for the research recommended by the peer review panel, and EPA would control the research protocols and select the contractors. The partnership was established in response to a recommendation of then Vice President Gore's National Performance Review as a way to reduce red tape and overcome the adversarial relationship typically present between EPA and its regulated parties (see "EPA 10" in National Performance Review 1993, From Red Tape to Results, Appendix A: Major Recommendations by Agency).
This partnership became acrimonious after EPA published its second draft risk assessment in 1992. EPA scientists interpreted the new science to mean that perchlorate was much more risky than they previously had thought; defense and industry scientists interpreted the new science to mean it was less risky. In early 2003, EPA published an interim risk management policy that relied on EPA's interpretation even though the 2002 draft risk assessment remained highly controversial and had not been finalized. This risk management document exacerbated the conflict, which EPA attempted to ameliorate by publishing a Q&A document. The 2003 Perchlorate State-of-the-Science Symposium was an effort sponsored by the defense and industry partners to independently review the new research. EPA was invited but declined to participate. Each of the papers resulting from the Symposium is reprinted in the adjacent tabs. A National Research Council committee relied on these papers extensively in its subsequent review and 2005 report.
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