Review of a Screening Level Risk Assessment for the Navy Air Facility at Atsugi, Japan (1998)

This document was prepared by the National Research Council's (NRC) Committee on Toxicology (COT) in response to a request fromthe Navy for an expedited independent review of a draft report titledScreening Level Air Human Health Risk Assessment, NAF Atsugi, Japan, which was prepared by the Navy Environmental Health Center (NEHC1998). A brief summary of COT's review is provided below and is followedby a detailed evaluation of the NEHC report.

The Jinkanpo incineration complex is a private waste-combustion anddisposal facility equipped with four incinerators, located approximately100 yards outside the Naval Air Facility (NAF) Atsugi, Japan. Manycarcinogenic and noncarcinogenic pollutants have been reported tobe emitted from the facility. In 1995, COT conducted a review ofthe Navy's preliminary risk-evaluation report (NEHC 1995) and concludedthat there was sufficient evidence to justify further sampling andevaluation of the air-pollution problem near NAF Atsugi (NRC 1995).Air concentrations of particulate matter and several toxic chemicals,including benzene and chromium, were reported to be near or abovethose generally associated with significant carcinogenic and noncarcinogenicrisks.

In response to COT's 1995 recommendation that additional air sampling be conducted,and because of the magnitude of the potential health risks to navalpersonnel and their families estimated in the 1995 NEHC report, NEHCcollected air samples in 1997 from nine sites in NAF Atsugi and prepareda draft report Screening Level Air Human Health Risk Assessment, NAF Atsugi, Japanadditional data and the Navy's 1998 draft screening-level risk-assessmentreport. Specifically, COT was requested to review the following:

1. The methods used by NEHC to assess health risks.

2. The scientific validity of the NEHC conclusions.

3. The NEHC evaluation of risks to susceptible subpopulations (i.e.,pregnant women, infants, and young children).

4. The uncertainties in the NEHC risk assessment.

On the basis of the data presented in the 1998 NEHC report and anevaluation of the data, COT concludes the following:

• COT generally concurs with NEHC's 1998 estimates of carcinogenic risk, which are similar to thosecalculated in 1995, even though the pollutants contributing to thoserisks are different.

• The air-sampling data indicate that concentrations of particulatematter less than 10 micrometers in aerodynamic diameter (PM₁₀) were above levels known to cause adverse health effects. However,NEHC's estimates of noncarcinogenic risk could not be verified, becausethe values used by NEHC to determine hazard indices were inappropriatelyconverted from reference concentrations (RfCs) or National AmbientAir Quality Standards (NAAQS) to reference doses (RfDs).

• COT found serious limitations in the methods used by NEHC to collectand analyze the air samples:

  • NEHC quality-assurance and quality-control (QA-QC) measures wereinadequate to provide accurate measurements of pollutant concentrations.

  • NEHC made an unsupported assumption that its selected backgroundsite (location 1) was substantially affected by point-source andfugitive emissions from the incinerator complex. No explanation ordata were provided in the NEHC report to indicate why that locationwas believed to be substantially affected by incinerator emissions.The meteorological data seem to indicate that location 1 might givea reasonable estimate of background concentrations of pollutants,at least as measured by PM ₁₀; these data indicate that the background concentration of PM₁₀ at Atsugi is high.

  • Incinerator operations were reportedly modified at times duringthe sampling periods as the operators of the incinerator became awareof the air monitoring. Such modifications of normal operating procedureslargely invalidate the measurement data and make them unusable forcharacterizing the incinerator as a source of measured pollutants.

• The NEHC data are insufficient to determine that the Jinkanpo incinerationcomplex was the major source of pollution contributing to the observedconcentrations of airborne contaminants during the air-sampling period.Such a determination would require better characterization of backgroundconcentrations.

• Some risk values were not passed through an adequate review or verificationprocess. The NEHC report states that risk values listed in the U.S.Environmental Protection Agency's (EPA) Integrated Risk InformationSystem (IRIS) and Health Effects Assessment Summary Tables (HEAST)have been peer reviewed (section 4.1, p. 14); however, subsequentdescriptions of the databases indicate that some of the values listedin HEAST are “provisional” because they have not been verified by an agency workgroup.

• The NEHC report inappropriately added risks based on acute and chronictoxicity end points and for different target populations, includingaddition of the risk of acute mortality in a person with cardiopulmonarydisease with the risk of chronic liver toxicity in a healthy adult.