Toxicological and Performance Aspects of Oxygenated Motor Vehicle Fuels (1996) / Chapter Skim
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4 HUMAN EXPOSURE
4 HUMAN EXPOSURE
Pages 67-74
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From page 67... ...
For example, occupational exposures of service-station attendants, automobile mechanics, and distribution workers may involve dermal as well as inhalation exposures. Similarly, the general public has the potential for dermal exposure during the handling and use of gasoline products, such as while cleaning and 67
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From page 68... ...
Each of these reports has sections on exposure assessment but takes a different approach to the issue. The primary focus of both reports is on inhalation exposures; substantially less attention has been devoted to the potential for dermal exposures and direct ingestion of oxygenated-fuel components.
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From page 69... ...
The exposure section of the OSTP report makes it clear that the cumulative exposure estimates are based on hypothetical scenarios, with one of the two designed to represent a "reasonable worst-case" scenario. However, the limitations can easily be missed by a reader in the subsequent risk characterization, in which the worst-case scenario is coupled with potency estimates to calculate lifetime cancer risks.
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From page 70... ...
Point estimates of concentrations from the microenvironmental measurements are combined with estimates in the OSTP report to provide cumulative estimates of exposure. To estimate potential human exposures, two exposure scenarios of hypothetical exposure sequences are constructed.
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From page 71... ...
These exposure data, however, can be used to provide a "reality" check for quantitative risk assessments and to construct boundary conditions or exposure ranges for MTBE concentrations that might be encountered in a variety of locations and activities. Using this information, the committee concluded that HEl could have performed a quantitative risk assessment using the exposure data represented by the meciiarz (approximately 0.13 ppb)
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From page 72... ...
The solid lines across the bars indicate median values. The numbers at the tOpS of the bars correspond tO the numbers in parentheses in the "Sampling Site" column of Table lII.3 (of HE!
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From page 73... ...
A comparative risk assessment requires data on the influence of MTBE on human exposure to these other constituents, and this committee believes that a quantitative framework should and could be established for this evaluation. Establishing a framework for consideration of all exposures will help identify important data gaps and provide for a direct comparison of the risk and benefits between conventional and oxygenated fuels.
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From page 74... ...
HET expressed the opinion that the data are too limited to calculate cumulative exposures for risk assessment. However, the committee's opinion is that the data are sufficient to bound a quantitative risk analysis and to develop a framework for conducting a comparative risk assessment of conventional and oxygenated fuels.
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