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DoD experienced threats to range sustainability and effective military training, decreased access to resources, and potential increases in weapon system costs — all from a draft risk assessment that was the subject of significant scientific debate. The perchlorate experience highlights the need for process reform to ensure that agency actions on emerging contaminants, achieve real public benefits without unintended adverse impacts on national security.

Historical compliance-based risk management strategies have proven insufficient to balance compliance with operational mission requirements. A reactive approach that limits itself to complying with regulations and standards after they are developed leaves little to no room for nimbly addressing new, unregulated contaminants and may result in financial and operational costs that are not supported by commensurate human health or environmental benefit. Significant changes in risk assessment policy and practice, including the strategic investment and use of chemical and site risk assessments, are required to transform a regulatory compliance-based environmental and occupational health management strategy into an operational capability/asset management strategy. DoD’s risk assessment policies require review and revision to ensure that DoD programs and service components cost-effectively assess the life-cycle risks posed by emerging chemicals to operational requirements. Such approaches can lead to both short- and long-term decreases in DoD’s costs of operating responsibly with respect to environment, safety and occupational health and to minimize cleanup costs.

The persistence of perchlorate in groundwater can be understood from its chemical and physical properties and its chemical reactivity. Although perchlorate is a powerful oxidizing agent, its notorious lack of reactivity can be understood from the requirement that reduction involves oxygen atom transfer. Because perchlorate is relatively unreactive, remediation schemes involving direct chemical or electrochemical reduction are not effective. The low hydration energy of perchlorate anions favors sorption on organic anion exchange resins. Remediation methods involving collection on such resins prior to reduction or some other means of disposal are feasible. Biological systems that naturally reduce and degrade perchlorate are also a potentially practical means of remediating perchlorate-contaminated groundwater in a cost-effective manner.

DoD experienced threats to range sustainability and effective military training, decreased access to resources, and potential increases in weapon system costs — all from a draft risk assessment that was the subject of significant scientific debate. The perchlorate experience highlights the need for process reform to ensure that agency actions on emerging contaminants, achieve real public benefits without unintended adverse impacts on national security.

Historical compliance-based risk management strategies have proven insufficient to balance compliance with operational mission requirements. A reactive approach that limits itself to complying with regulations and standards after they are developed leaves little to no room for nimbly addressing new, unregulated contaminants and may result in financial and operational costs that are not supported by commensurate human health or environmental benefit. Significant changes in risk assessment policy and practice, including the strategic investment and use of chemical and site risk assessments, are required to transform a regulatory compliance-based environmental and occupational health management strategy into an operational capability/asset management strategy. DoD’s risk assessment policies require review and revision to ensure that DoD programs and service components cost-effectively assess the life-cycle risks posed by emerging chemicals to operational requirements. Such approaches can lead to both short- and long-term decreases in DoD’s costs of operating responsibly with respect to environment, safety and occupational health and to minimize cleanup costs.

The frequency of detection of perchlorate impacts to soil, groundwater and surface water, unrelated to military activities, is likely to increase as water utilities analyze for this constituent as part of their UCMR monitoring programs. Based on emerging product and process information, perchlorate is present (intentionally or not) in many more products and processes than initially understood. Furthermore, evidence exists that perchlorate can be formed naturally in evaporate deposits and through atmospheric mechanisms.

The U.S. DOD, NASA and related defense contractors are likely to be the most significant domestic users of perchlorate in North America, and as such, a significant percentage of identified groundwater perchlorate impacts are attributable to DOD, NASA, and related defense contractor facilities. However, cases exist, and many more are likely to surface, where perchlorate impacts result from combinations of military, non-military, and/or natural inputs.

The field of microbial perchlorate reduction has clearly advanced significantly in a very short period from a poorly understood metabolism to a burgeoning scientific field of discovery. As outlined above, there is now a much greater appreciation of the microbiology involved and the application of the knowledge to the successful treatment of contaminated environments. Overall, the future is promising even though research in this field is still in its infancy. Nothing is known of the evolutionary root of this metabolism. From a biogeochemical perspective, a better understanding of how perchlorate is formed in the natural environment and what geochemical conditions are required for its formation might give some insight into plotting the metabolism against a realistic evolutionary timeline. From a microbial perspective, it will be important to look for this metabolism in more extreme environments such as hypersaline or hyperthermophilic environments to obtain DPRB isolates across a broader phylogeny to establish a broad-base molecular chronometer. With the development of this field comes a better understanding of the ideal electron donors available and the individual factors which truly control the activity of the these organisms in-situ allowing for the design of more effective and robust enhanced in situ bioremediation technologies.

DoD experienced threats to range sustainability and effective military training, decreased access to resources, and potential increases in weapon system costs — all from a draft risk assessment that was the subject of significant scientific debate. The perchlorate experience highlights the need for process reform to ensure that agency actions on emerging contaminants, achieve real public benefits without unintended adverse impacts on national security.

Historical compliance-based risk management strategies have proven insufficient to balance compliance with operational mission requirements. A reactive approach that limits itself to complying with regulations and standards after they are developed leaves little to no room for nimbly addressing new, unregulated contaminants and may result in financial and operational costs that are not supported by commensurate human health or environmental benefit. Significant changes in risk assessment policy and practice, including the strategic investment and use of chemical and site risk assessments, are required to transform a regulatory compliance-based environmental and occupational health management strategy into an operational capability/asset management strategy. DoD’s risk assessment policies require review and revision to ensure that DoD programs and service components cost-effectively assess the life-cycle risks posed by emerging chemicals to operational requirements. Such approaches can lead to both short- and long-term decreases in DoD’s costs of operating responsibly with respect to environment, safety and occupational health and to minimize cleanup costs.

The identification and analysis of the genes encoding perchlorate reductase and chlorite dismutase has provided not only a building block for pathway understanding, but has also provided a tool for bioremediative and phylogenetic studies. On-going genome sequencing will further facilitate transcriptional profiling under perchlorate-reducing conditions via microarray analyses. This analysis will give a more inclusive look into transcriptional expression patterns associated with the perchlorate metabolism. While further advancements in the genetic analysis of perchlorate-reducing bacteria continue, the recent development of a genetic system in will provide an invaluable tool for corroborating microarray results and solidifying hypotheses regarding microbial perchlorate metabolism.

There are currently many unanswered questions surrounding the prevalence of perchlorate in the environment, the possible exposures and effects, and the risk management strategies available to manage perchlorate contamination. Further information must be obtained in each of these areas in order to develop successful and appropriate strategies for handing perchlorate contamination now and in the future. Because of the uncertainty involved in evaluating toxicological data, the states and federal agencies using this information may use and interpret it somewhat differently to promulgate different standards and advisory levels. It is important to note that the status of the knowledge of perchlorate exposure and risks continues to evolve and it will be essential to periodically re-evaluate what is known about this chemical. However, the reference dose recommended by National Research Council and adopted by the U.S. Environmental Protection Agency will protect the health of even the most sensitive groups of people over a lifetime of exposure.

Scientifically valid exposure assessment is crucial to risk assessment, risk management, and prevention of environmental disease. Biomonitoring is an excellent tool for evaluating human exposure to perchlorate from all sources, and often provides complementary information to environmental data. Analytical methods for perchlorate biomonitoring must be adequately sensitive and selective to detect sub-parts-per-billion levels in complex matrixes. Through improved exposure assessment we can better evaluate the relevance of environmental perchlorate to human exposure and health.

Scientifically valid exposure assessment is crucial to risk assessment, risk management, and prevention of environmental disease. Biomonitoring is an excellent tool for evaluating human exposure to perchlorate from all sources, and often provides complementary information to environmental data. Analytical methods for perchlorate biomonitoring must be adequately sensitive and selective to detect sub-parts-per-billion levels in complex matrixes. Through improved exposure assessment we can better evaluate the relevance of environmental perchlorate to human exposure and health.