Review of the Air Quality Criteria Document for Particulate Matter

health-response time at ambient levels remains unknown, has two major problems. First, itis inconsistent with the known health-response times of both O 3 and CO. As a result, theimpacts of O 3 and CO on the regression are not properly characterized. Second, the 24-houraverages of O 3 and CO do not correlate perfectly with the peak 1-hour or 8-hour values thatare the measures associated with their health effect endpoints. Worse yet, urban sites tend tohave higher peak O 3 than rural sites, but rural sites tend to have higher 24-hour O 3concentrations than urban sites. For the spatial analysis, NMMAPS used annual meanswhen it was appropriate to use the means of the 1-hour or 8-hour daily maxima. Cleanerareas and rural areas generally have higher annual average ozone values than more pollutedurban areas. Consequently, the results involving O 3 and CO are likely not meaningful.6. The Reanalysis Team also used the same annual average O 3 for the H6CS reanalysis.Although the report states that they used the annual mean of the daily 1-hour maxima for theACS reanalysis, they used the annual average as well because the ozone values presented inappendix G of the report are much too low to be the average of the 1-hour maxima. Anotherproblem with computing a valid annual mean for ozone is that many locations only measureozone during the ozone season, which has a different definition depending upon the localclimatology. In Michigan, which is typical of northern states, ozone is only measured from April1 to September 31, whereas in Southern California, it is measured year round. Consequently, Ihave the same similar concerns for the Reanalysis multi-pollutant results as I have for theNMMAPS results.Chapter 91. P 9-2, line 30 – Delete “in general.”2. Table 9-2, organic carbon row, anthropogenic column – delete “emitted by motor vehicles”since there are other man-made sources of hydrocarbons.A - 87