Review of Studies of Possible Toxic Effects from Past Environmental Contamination at Fort Detrick A Letter Report (2012) / Chapter Skim
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Letter Report
Letter Report
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Army, the National Research Council established the Committee to Review Studies of Possible Toxic Effects from Past Environmental Contamination at Fort Detrick. The committee was charged to evaluate independently the scientific and methodologic quality and rigor of two studies: a public-health assessment conducted by the Agency for Toxic Substances and Disease Registry and a cancer investigation conducted by the Maryland Department of Health and Mental Hygiene and the Frederick County Health Department.
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The reports to be reviewed include an assessment conducted by the Agency for Toxic Substances and Disease Registry (ATSDR) in 2009, and the interim and final reports of an ongoing cancer assessment by the Maryland Department of Health and Mental Hygiene and the Frederick County Health Department (MDHMH/FCHD)
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However, the committee was constituted to address only the concerns about risks related to groundwater contamination in Area B; it was not charged or constituted to evaluate exposures that might have occurred in Area A, potential exposures to Agent Orange, or risks posed by pathogens studied at the biocontainment laboratories. The committee is aware of research efforts that are under way, including those of the Kristin Renee Foundation, members of the FCHD Community Technical Advisory Committee for the Cancer Cluster Investigation, and a graduate student at the University of Maryland.
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Exposure Assessment To estimate potential human exposure to drinking-water contaminants, ATSDR considered the sources of the contamination, pathways by which the groundwater could have been contaminated, routes by which people could have been exposed, and possible contaminant concentrations. It considered PCE and TCE to be the groundwater contaminants of concern because they were detected at concentrations higher than EPA's maximum contaminant level for these solvents in drinking water (5 ppb)
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The scientific soundness and quality of the conclusions that can be drawn from such studies are questionable because of the inherent weakness of the available exposure data that can be used to verify estimates of past exposure. Although ATSDR acknowledged the limitations of its exposure assessment, the committee judged that the agency's decision to conclude that past exposures were unlikely to produce any harmful health effects does not capture the scientific uncertainty about exposures that occurred before 1992.
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Exaggerated estimates of the duration of human exposure offset to some degree any underestimation of the average concentrations of PCE and TCE in drinking water. Overall, the committee concluded that the assumption that exposures were continuous for 40 years probably sets an upper bound on exposures; actual exposures probably were lower.
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.2 Furthermore, ATSDR's assessment did not consider cancer slope factors for inhalation (EPA 1991; Washington State Department of Ecology 2004) or whether the cancer risks associated with PCE and TCE should be summed to determine total cancer risk (EPA 2009)
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no public-health hazard. ATSDR concluded that past exposure to PCE or TCE via contaminated drinking-water wells was "unlikely to produce any harmful health effects, including cancer".
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Answers to Charge Questions about the Maryland Cancer Investigation Is the report scientifically sound and of high quality? The analyses of cancer incidence rates in Frederick County and the selected census tracts were in general scientifically sound and of high quality, given the typical limitations of cancer-surveillance data from state registries.
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When another seven census tracts were added to the original three, expanding the buffered area around Fort Detrick to about a 2-mile radius, there were no significant increases in all cancers or in specific types of cancer around Fort Detrick in the period 1992-2008 compared with Frederick County or the state as a whole. According to an earlier analysis, the age-adjusted rate of all cancers in Frederick County had increased from 2001 to 2006 compared with both Maryland and the United States.
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(To compare a part with a whole that contains it also requires a different form of statistical analysis that is based on p values.) An analysis that compared the census tracts surrounding Fort Detrick with the remainder of Frederick County would more clearly describe any differences in cancer rates between the census tracts and the rest of the county.
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Whereas the number of cases of lymphoma by subtype and the total number of 2001–2006 cases in the Maryland Cancer Registry may not be sufficient to provide definitive findings, the additional analyses could be valuable in addressing community concerns regarding experience of cancer in the vicinity of Fort Detrick, and they would render the MDHMH–FCHD report more complete in its analysis of pertinent cancer data. Because of the limitations inherent in cancer-cluster investigations, no study will be able to provide definitive findings, regardless of the number of cases.
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It would be an upper bound because cracks and holes in foundations or floors might have opened after vapor concentrations receded. Identify the people who live or lived in the homes susceptible to vapor intrusion and conduct a health survey.
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to unusual concentrations of contaminants in groundwater is discovered. To help members of the Frederick County community to sort through the evidence of possible links between Army activities and public health, the committee suggests first that all parties recognize that risk depends on the existence of completed exposure pathways (simple proximity to Fort Detrick does not in itself impart increased risk)
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For example, the ATSDR PHA found it unlikely that Area B groundwater contamination caused off-post health effects. The present committee judges that the exposure data are inadequate for ruling out health consequences of possible past exposures and that a more appropriate conclusion would have been that the groundwater presented an indeterminate public-health hazard.
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Presentation at the First Meeting of the Committee to Review Studies of Possible Toxic Effects from Past Environmental Contamination at Fort Detrick, May 16, 20011, Frederick, MD. CalEPA (California Environmental Protection Agency)
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Overview. Presentation at the First Meeting of the Committee to Review Studies of Possible Toxic Effects from Past Environmental Contamination at Fort Detrick, May 16, 2011, Frederick, MD.
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:321-339. MDHMH/FCHD (Maryland Department of Health and Mental Hygiene and the Frederick County Health Department)
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