Review of the Air Quality Criteria Document for Particulate Matter

P 7- 27, L 15: What does “comparable respiratory intensity levels” mean? I don’t know what“intensity level” might imply.P 7- 27, L 22: Again, has there been any validation? It is important throughout the chapter toindicate whether or not models have been validated against actual measurements.P 7-28, L 9: The statement is incorrect. The study did not measure the “volume density ofdeposition”, whatever that might be. The study measured, using a morphometric techniquebased on volume density, the retained material. A post hoc study of tissue cannot evaluatedeposition, but only the amount and location of retained material.P 7- 28, L 12-14: The statement is incorrect. It is not true that “different cells contact retainedparticles” in the two species. The difference was not absolute. There was relatively morematerial in the interstitium in one species and relatively more in the alveolar lumen in the other,but there was some material in both compartments in both species.P 7- 28, L 21: The point is that there can be greater differences between abnormal humans andnormal rats. The present wording doesn’t convey this; it suggests that the greater difference youare talking about is between humans and rats.P 7-28, L 23-27: This section inappropriately brings response into the dosimetric picture. Doseis dose regardless of response – these are related, but separate, issues. Interspecies doseextrapolation per se has nothing to do with interspecies differences in response or dose-responserelationships. Comparative response has to do with both differences in both dose and response,but comparative dose has nothing to do with differences in response.P 7.29, L 3: In summary, this section could greatly benefit from some tables or figures showingexample results and comparisons. It also needs attention to which model predictions have beenvalidated.P 7-32, L 23-24: The magnitude of response also has to do with PM composition, not just withparticle number.P 7- 33, L 1-11: Lymphatics should be mentioned in this paragraph.P 7- 33, L 14: Do you mean 5% by mass or number?P 7- 33, L 17-18: Alveolar surface fluid is also transported, at least in some in part, up theairways. Surfactant of alveolar origin has been reported in the surface fluid of conductingairways. If this is true, then you should mention this path rather than implying that all PMderivedmaterial solubilized in alveolar fluid is absorbed through the epithelium.P 7-34, L 8: What do you mean by “nonuniform”? Do you mean spatially or temporally nonuniformwithin individuals, or are you referring to variability among individuals?P 7- 35, L 5: You need to clarify throughout this chapter whether the statements aboutdeposition site are derived from measurements or whether these are assumptions from depositionmodels. Most, if not all, are from the latter, which assume plug flows that are not likely to beabsolute.P 7-35, L 22: Deposition was “estimated”, not “calculated”. The latter term implies a certainty,or direct measurement, that doesn’t exist here.P 7-37, L 25-26: The phagocytic activity need not necessarily be decreased, it could be simplyoverwhelmed. More particles could reach the interstitium because of either or both effects.A - 22