Exploring associations between multipollutant day types and asthma morbidity: epidemiologic applications of self-organizing map ambient air quality classifications (13 page pdf, John L. Pearce, Lance A. Waller, James A. Mulholland, Stefanie E. Sarnat, Matthew J. Strickland, Howard H. Chang and Paige E. Tolbert, Environmental Health, Jun. 23, 2015)
Today we review research conducted in Atlanta on the relationship between exposure to groups of up to 10 pollutants and the health impacts brought on by asthma. Results indicate the same high relationship between adverse health impacts and higher levels of pollution that has been seen in examining the impacts of a single pollutant. When groups of pollutants were examined, the highest asthma morbidity was seen on days that were warm and dry with emissions from vehicles one of the three highest classes. This shows the value of looking at the combined impacts of several pollutants.
“extreme NO3 days that occurred 7 % of the time under cool, wet, stable conditions. This agrees well with understanding of how low temperatures and high relative humidity contribute to the formation of nitrate rich aerosols in Atlanta”
“11 % of days … were dominated by well-above average to extreme conditions for several primary pollutants
such as CO, NO2, NOX, EC, and OC. Consistent with these relatively cold dirty days are the high pressure, low wind speeds, and low humidity conditions suggestive of poor atmospheric mixing and potential inversions”
“high ratios of OC/EC .. are indicative of days dominated by mobile source emissions from gasoline..however, .. is far less frequent (3.3 % of days) and highlights days when several pollutants are two to three times higher than average – a scenario we might a priori describe as the most hazardous air quality scenario in our study."
“We found significant associations of increased asthma morbidity for (1) days that were most warm, with low winds and humidity .. and very high levels for secondary pollutants (O3 and ammonium sulfates); (2) days that were the driest and most stable .. with very high primary pollutants from vehicles (CO, NOx, EC, and OC), and (3) days that were generally warm, stable and dry .. with elevated levels for both primary and secondary pollutants.”