Review of the Army's Technical Guides on Assessing and Managing Chemical Hazards to Deployed Personnel (2004) / Chapter Skim
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5 Process for Establishing and Applying Military Exposure Guidelines
5 Process for Establishing and Applying Military Exposure Guidelines
Pages 91-130
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From page 91... ...
The basic approach to determining air MEGs was to review the exposure guidelines of other agencies, use a hierarchical scheme to select the most appropriate guideline for the exposure duration of interest, and then adjust that guideline to meet the military's needs, if necessary. Air MEGs were developed for exposures of 1 hour, 8 hours, 14 days, and 1 year.
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From page 92... ...
Above AEGL-3, the general population could experience life-threatening health effects or death. These levels were developed for exposure durations of 10 minutes (min)
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From page 93... ...
. 8-Hour Air MEGs Derivation RD-230 indicates that the exposure duration of 8 hours was selected to
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From page 94... ...
In a number of cases, the 8hour air MEGs are the same as the 1-hour air MEGs for minimal effects. Evaluation Because relatively few 8-hour AEGLs have been derived, TLVs are the preferred sources for the 8-hour MEGs.
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From page 95... ...
exposures. Although RD-230 states that the TLVs were not considered protective for continuous exposures of over 24 hours to 14 days, the TLVs were extrapolated down from working lifetime values to 14-day continuous exposure values.
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From page 96... ...
For the 14-day values based on TLVs, adjusting the TLVs for the change from 8 hour/day, 5 day/week to 24 hour/day, 7 day/week and for the higher breathing rates of military personnel (i.e., 14-day air MEGs = TLVs × 5 days/7 days × 10 m3/29.2 m3) is reasonable for systemic chemicals when dose rate is not the determining factor and only total dose dictates effects (Gaylor 2000)
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From page 97... ...
1-Year Air MEGs Derivation The one-year air MEG is defined by USACHPPM (2002) as "The airborne concentration for a continuous exposure up to 1 year (365 days, 24 TABLE 5-1 Sources for 14-day Air MEGs Exposure Source Duration and Portion of Lifetime USACHPPM Adjustments in Reference Frequency Protected 14-Day Air MEGs CEGL 90 days, 90 days No adjustments were made continuous MRL 1-14 days, daily 1-14 days No duration or ventilation rate adjustments were made TLVs 8 hours/day, 5 Working lifetime Adjustments to continuous days/ week 14-day and military ventilation rates
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From page 98... ...
discrepanciesbetweenthosevaluesexisted,USACHPPMreviewedthedata and selected the final 1-year air MEGs. Derivation of PMEG-Ls USACHPPM developed military "noncancer" risk concentrations (MRCs)
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From page 99... ...
Those unit cancer risks also were converted from risk per microgram per cubic meter to risk per milligram per kilogram per day, assuming a body weight of 70 kg and an inhalation rate of 20 m3/day. To calculate the MCRC, the target cancer risk (TCR)
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From page 100... ...
The State of California has hundreds of values that were derived following a standard procedure similar, but not identical to that used by EPA. The subcommittee recommends that HEAST values not be used to derive long-term air MEGs, because the quality of those assessments is not as strong as that of the other guidelines.
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From page 101... ...
Varying Exposure Durations One overarching problem is that the 1-year air MEGs are based on source references with varying exposure durations. Table 5-2 summarizes the exposure durations and frequencies associated with the sources used by USACHPPM in developing the 1-year air MEGs.
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From page 102... ...
Thus, approaches that were adequate for the underlying methods might need to be revisited when USACHPPM revises the MEGs. For 1-year air MEGs that are based on adjusted TLVs, there is an additional interpretative issue, because the TLVs address worker-lifetime exposure.
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From page 103... ...
The NAAQS have a variety of durations (some are for 24 hours, some are annual) and are set to protect susceptible subpopulations.
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From page 104... ...
However, selecting a military value lower than the NAAQS should be re-evaluated, especially considering the more robust health of the military population. As mentioned above, the most straightforward approach to dealing with the criteria air pollutants might be to consult with EPA and address the military population explicitly.
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From page 105... ...
DRINKING WATER GUIDELINES This section reviews USACHPPM's considerations for contaminated drinking water. Packaged and treated water is not always available during deployments.
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From page 106... ...
As with the air MEGs, certain adjustments were performed to make the values more relevant to the military population. For example, the daily water consumption rates of deployed personnel are much higher (between 5 and 15 liters [L]
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From page 107... ...
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From page 108... ...
concentrations of carcinogenic chemicals with the corresponding long-term water MEGs. The riskspecific concentrations were obtained from EPA's drinking water regulations and HAs or from IRIS, and they all assumed a lifetime of exposure.
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From page 109... ...
In the case of dermal exposures, the subcommittee performed rough risk calculations using data for some volatile and semivolatile organic compounds, such as trichloroethylene and benzo(a) pyrene, to evaluate dermal exposure during showering and agrees with USACHPPM that risk from water consumption generally subsumes that from dermal absorption.
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From page 110... ...
Soil MEGs were derived in a manner consistent with the derivation of risk-based screening levels for the general population with adjustments added to better represent the characteristics of deployment exposures. The chemicals selected for soil MEG development were described by USACHPPM as "consistent with those used to develop drinking water guidelines." The rationale for the selection process is that ingestion is the primary exposure route for both soil contaminants and drinking water contaminants.
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From page 111... ...
Critical assumptionsusedtoestimate oral, inhalation, and dermal exposures include soil ingestion rate, inhalation rate, skin surface area, skin adherence factors, and dermal absorption. In RD-230, an average soil ingestion value of 265 mg/day was derived by assuming that soldiers have equal numbers of high ingestion and low ingestion days while deployed.
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From page 112... ...
. DOD has modified the model further by increasing the target blood lead concentration from 10 :g/dL for the fetus to 30 :g/dL for an adult worker.
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From page 113... ...
Toxicity Data As noted above in the recommendations for the derivation of air MEGs, the subcommittee recommends that USACHPPM avoid using toxicity val
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From page 114... ...
Once those flaws are corrected, it is likely that the inhalation pathway will not have a significant influence on the soil MEGs for semivolatile and inorganic chemicals. The adjustments made to oral toxicity values for deriving the water MEGS were judged to be appropriate, and their use in deriving soil MEGs is also appropriate.
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From page 115... ...
Asdescribedabove,thecriticalassumptionsusedtoestimateinhalation, oral, and dermal exposures include inhalation rate, soil ingestion rate, skin surface area, skin adherence factors, and dermal absorption. The inhalation assumptions were addressed in the review of air MEGs.
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From page 116... ...
Those studies should be considered in re-evaluating adherence factors for soil MEGs. In particular, DOD should consider using high and low soil adherence values with the same frequency that high and low soil ingestion values are used.
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From page 117... ...
It is vital to know if the primary risk is from inhalation, dermal exposures, or soil ingestion. Soil ingestion is relatively easy to avoid, whereas inhalation can not be avoided without a respirator.
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From page 118... ...
The adult lead model was designed to use a central tendency estimate of soil ingestion. To the extent that the DOD value is an upper-end estimate, its use will lead to substantial overprediction of blood lead levels.
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From page 119... ...
Given the availability of reliable tests for blood lead levels, it might be feasible to periodically monitor blood lead levels in troops exposed to soils whose lead levels exceed the soil MEG to ensure that target blood lead levels are not also exceeded. Consideration of Acute Toxicity The soil MEGs are set for 1-year exposures.
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From page 120... ...
Under this new scheme, it would not be appropriate for the health-based MEGs to be used in conjunction with the military's mission risk assessment matrix to evaluate mission risks, as is currently recommended in TG-230. Rather, the subcommittee envisions that MEGs will be used as guidelines to assess health risks and the potential risk-management options for reducing or eliminating those risks.
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From page 121... ...
During longer-term deployments, deployed personnel might be exposed to low levels of common contaminants through various environmental media. In those longer-term scenarios, personnel could inhale contaminants in air that were volatilized from soil and/or water; ingest contaminated water; and/or experience dermal exposures from bathing or from direct contact with contaminated soils.
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From page 122... ...
. The subcommittee agrees that conventional algorithms used to assess health risks from multiple chemicals are not useful for assessing mission risks.
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From page 123... ...
Cumulative exposures involve exposures to multiple chemicals. EPA defines cumulative risk as the likelihood of occurrence of an adverse health effect from exposure to multiple chemicals that have common modes of toxicity from all routes and pathways.
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From page 124... ...
As described in previous sections, long-term MEGs for noncancer effects were based preferentially on subchronic toxicity values. However, in the many cases where only chronic toxicity values were available, those values were used.
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From page 125... ...
Overall, the MEGs must be re-evaluated and revised to make them more relevant to force health protection and more consistent with each other. Ideally,USACHPPMwilldevelopasetofprinciples,guidelines,andprocedures for developing MEGs de novo from the primary toxicology data.
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From page 126... ...
-- Re-evaluate the approach used to assess dermal exposures to CWAs. · Establish risk-managementframeworkthatfocusesonactionplans (i.e., responses)
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From page 127... ...
However, it would avoid the more time-consuming tasks of literature searches and evaluations of the primary literature while providing a transparent, systematic, and uniform method of applying adjustments to exposure durations, inhalation rates, and water intake rates. It would also standardize the treatment of susceptible subpopulations.
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From page 128... ...
1994. Assessing the relationship between environmental lead concentrations and adult blood lead levels.
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From page 129... ...
2002e. 2002 Edition of the Drinking Water Standards and Health Advisories.
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From page 130... ...
A Companion Docu ment to USACHPPM Technical Guide (TG) 230 Chemical Exposure Guidelines for Deployed Military Personnel.
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