8.2.6.2 Effects of weather on concentrations of other air pollutants

Concentrations of air pollutants in general, and fine particulate matter (PM) in particular, may change in response to climate change because their formation depends, in part, on temperature and humidity. Air-pollution concentrations are the result of interactions between variations in the physical and dynamic properties of the atmosphere on time-scales from hours to days, atmospheric circulation features, wind, topography and energy use (McGregor, 1999; Hartley and Robinson, 2000; Pal Arya, 2000). Some air pollutants demonstrate weather-related seasonal cycles (Alvarez et al., 2000; Kassomenos et al., 2001; Hazenkamp-von Arx et al., 2003; Nagendra and Khare, 2003; Eiguren-Fernandez et al., 2004). Some locations, such as Mexico City and Los Angeles, are predisposed to poor air quality because local weather patterns are conducive to chemical reactions leading to the transformation of emissions, and because the topography restricts the dispersion of pollutants (Rappengluck et al., 2000; Kossmann and Sturman, 2004).

Evidence for the health impacts of PM is stronger than that for ozone. PM is known to affect morbidity and mortality (e.g., Ibald-Mulli et al., 2002; Pope et al., 2002; Kappos et al., 2004; Dominici et al., 2006), so increasing concentrations would have significant negative health impacts.