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Subtask B: Exposure Assessment and Subtask D: Risk Characterization The choice of exposure scenarios in Subtask B of the revised risk assessment should be a "most likely" or average scenario and RME which incorporates upper 95% confidence limit for the mean data and RME exposure parameters (from Region 9 guidance) . Use of the worst-case scenario in risk assessment should be reserved for instances in which the RME cannot be calculated. Subtask C: Dose-Response Assessment No rationale is provided for the development of toxicological profiles for a maximum of eight chemicals. As stated earlier, little detail is provided in the present comments and the baseline risk assessment for the selection of chemicals of concern. The selection of a maximum of eight chemicals seems premature at this point. Subtask D: Risk Characterization Summing noncarcinogenic hazard quotients across pathways for each and/or all chemicals involves a number of limitations (see pages 8-14 in RAGS for a more detailed description) . Most importantly, summing noncarcinogenic hazard quotients should be applied to compounds that induce the same effect by the same mechanism of action otherwise there exists the potential to overestimate adverse health effects. GENERAL COMMENTS General Comment 1 The fact that most of the area is paved does not eliminate all contact with volatile solvents because the pavement may retard the volatilization of these solvents and may be a source for future exposure. Future development of cracks in the pavement may cause a localized release of volatile solvents and may be of concern to those present in the area. 7. General Comment 4 An indication of methods to be used to evaluate future plume development would be helpful (modeling, field sampling) . SPECIFIC COMMENTS Specific Comment 2 EPA suggests the use of "chemicals of concern" instead of "indicator chemicals. " Also, see earlier comment on "Hazard II-2