• RfCs are still converted to RfDs in the current risk assessment. It was recommended (NRC 1998) that RfCs themselves be used to calculate hazard indexes, and the present subcommittee reiterates that recommendation.

  • Exposures to inhaled pollutants are converted to estimated doses in milligrams per kilogram per day. That conversion is not appropriate for inhaled pollutants with portal-of-entry effects. Therefore, the present subcommittee reiterates the recommendation that exposure concentrations, rather than doses, be used for inhaled pollutants. Indeed, in a comprehensive risk assessment, exposure and dose estimates should be made on a route-specific basis (and not combined), before comparison with route-specific toxicities to evaluate carcinogenic risks and hazard quotients. It is the route-specific risk estimates or hazard quotients that may be combined to provide a summary risk estimate or hazard index; the route-specific doses should not be combined.

  • The contribution of pollutants from the solid-waste piles and liquid-waste sources at the incinerator facility are not explicitly addressed. Although pollutants from such wastes are presumably measured in the air samples, those wastes do not appear to have been considered as sources in the airdispersion modeling. They also do not appear to have been considered as potential sources in the computation of the periods when particular sites were downwind.

  • The 1998 NEHC report was criticized for not providing sufficient information on the number of air samples collected, the specific times of collection, sampling times for the maximal detected concentration, averaging times for exposure-point measurements, and the rationale for sampling some sites more than others. The 2000 NEHC draft summary report still does not provide enough information on the observational design and methods. Some of that information is present in supporting documents (Pioneer 2000; Radian 2000a,b,c,d) and should be included in the NEHC report, but even the supporting documents do not provide all the necessary information.

  • Values below the limit of measurement have been replaced by half the limit of measurement in calculating averages. Such replacement might not be appropriate—a sensitivity analysis for the effect of this assumption should be performed.

APPENDIX A

Objectives of the NEHC Risk Assessment

As discussed previously, the subcommittee noted many different, and sometimes conflicting, objectives within the NEHC draft summary report and the supporting documentation from the contractors. This appendix provides specific examples of differing objectives, and some possible effects of those differences on the risk assessment.

In the Pioneer document (Pioneer 2000; p. 1), the purpose of the risk assessment is stated to be:

  1. Estimate the potential human health risks to U.S. Navy personnel and their families and other individuals living and working on NAF Atsugi, Japan resulting from exposure to constituents of concern (COCs) in soil, ambient air, indoor air, and indoor dust.

  2. Estimate the contribution of the risk attributable to emissions from the SIC.

Suitable sampling plans could be designed to help answer both of those questions; however, the datacollection and analysis requirements for each question are different, therefore, both objectives must be considered in sampling design.

The purposes of the risk assessment, however, are not consistently incorporated into design objectives



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Review of the US Navy's Human Health Risk Assessment of the Naval Air Facility at Atsugi, Japan RfCs are still converted to RfDs in the current risk assessment. It was recommended (NRC 1998) that RfCs themselves be used to calculate hazard indexes, and the present subcommittee reiterates that recommendation. Exposures to inhaled pollutants are converted to estimated doses in milligrams per kilogram per day. That conversion is not appropriate for inhaled pollutants with portal-of-entry effects. Therefore, the present subcommittee reiterates the recommendation that exposure concentrations, rather than doses, be used for inhaled pollutants. Indeed, in a comprehensive risk assessment, exposure and dose estimates should be made on a route-specific basis (and not combined), before comparison with route-specific toxicities to evaluate carcinogenic risks and hazard quotients. It is the route-specific risk estimates or hazard quotients that may be combined to provide a summary risk estimate or hazard index; the route-specific doses should not be combined. The contribution of pollutants from the solid-waste piles and liquid-waste sources at the incinerator facility are not explicitly addressed. Although pollutants from such wastes are presumably measured in the air samples, those wastes do not appear to have been considered as sources in the airdispersion modeling. They also do not appear to have been considered as potential sources in the computation of the periods when particular sites were downwind. The 1998 NEHC report was criticized for not providing sufficient information on the number of air samples collected, the specific times of collection, sampling times for the maximal detected concentration, averaging times for exposure-point measurements, and the rationale for sampling some sites more than others. The 2000 NEHC draft summary report still does not provide enough information on the observational design and methods. Some of that information is present in supporting documents (Pioneer 2000; Radian 2000a,b,c,d) and should be included in the NEHC report, but even the supporting documents do not provide all the necessary information. Values below the limit of measurement have been replaced by half the limit of measurement in calculating averages. Such replacement might not be appropriate—a sensitivity analysis for the effect of this assumption should be performed. APPENDIX A Objectives of the NEHC Risk Assessment As discussed previously, the subcommittee noted many different, and sometimes conflicting, objectives within the NEHC draft summary report and the supporting documentation from the contractors. This appendix provides specific examples of differing objectives, and some possible effects of those differences on the risk assessment. In the Pioneer document (Pioneer 2000; p. 1), the purpose of the risk assessment is stated to be: Estimate the potential human health risks to U.S. Navy personnel and their families and other individuals living and working on NAF Atsugi, Japan resulting from exposure to constituents of concern (COCs) in soil, ambient air, indoor air, and indoor dust. Estimate the contribution of the risk attributable to emissions from the SIC. Suitable sampling plans could be designed to help answer both of those questions; however, the datacollection and analysis requirements for each question are different, therefore, both objectives must be considered in sampling design. The purposes of the risk assessment, however, are not consistently incorporated into design objectives

OCR for page 21
Review of the US Navy's Human Health Risk Assessment of the Naval Air Facility at Atsugi, Japan throughout the documents. In Section 1.3 (Radian 1998a), the following two objectives for the field sampling are stated: Define the extent of chronic and acute risk to NAF Atsugi base personnel likely to be caused by the operation of the Jinkanpo Incineration Complex; and Define the contribution of the risk attributed by the Jinkanpo Incineration Complex. Though similar to the overall objectives, those two objectives overlap with each other and do not include the objective of estimating the total risk to individuals living at NAF Atsugi. Those objectives are slightly altered in the sampling plans for individual media. In Section 3.1 (Radian 1998c), the following objectives for the soil monitoring are stated: What is the dermal and incidental ingestion exposure due to soil for sensitive receptors likely to be impacted by the Jinkanpo Incineration Complex? What is the extent of deposition of particulates in the soil from the Jinkanpo Incineration Complex?” Similarly, Section 3.2 (Radian 1998a) states the following as objectives for indoor air sampling: What is the inhalation exposure risk for sensitive receptors in buildings likely to be impacted by the Jinkanpo Incineration Complex? ” In both those examples, a new focus on “sensitive receptors” has been included, but the exact meaning of “sensitive receptors” and how they fit with the overall objectives of the risk assessment are not explained. In addition, those objectives do not include examining the overall state of the soil and air, but only examining the contributions from the incinerator complex. Section 3.3 (Radian 1998a) contains the strategy that is designed to answer the following questions for the ambient air sampling: What is the outdoor inhalation exposure at the elementary school? What is the basewide inhalation exposure due to airborne contaminants which are likely to have been introduced by the Jinkanpo Incineration Complex? Can the airborne contaminants detected directly downwind of the Jinkanpo Incineration Complex be attributed in part to sources besides the incinerator? How does the local air quality compare with the U.S. EPA National Ambient Air Quality Standards (NAAQS) for criteria pollutants?” Only the last of those questions asks about air quality over NAF Atsugi as a whole (as would be required for the first purpose of the risk assessment) as opposed to the contribution from the incinerator, and even then it discusses only US criteria pollutants. Similarly, Section 3.4 (Radian 1998a) contains the strategy that is designed to answer the following questions for the FTIR sampling: What is the contribution of the Jinkanpo Incineration Complex to the air quality at the base? Are there temporal variations in VOC and acid gas concentrations at the base? Are there variations in VOC and acid gas concentrations across the area of the base? What is the continuous inhalation exposure of NAF personnel to VOC and acid gas concentrations?