Widespread adoption of “cool roofs” – typically made of light-colored materials that reflect a large fraction of the sun’s rays – has the potential to increase certain types of air pollution, researchers from the South Coast Air Quality Management District and the University of Southern California reported yesterday in the Proceedings of the National Academy of Sciences. . . .The widespread adoption of cool roofs will decrease annual average daily high temperature in the basin, the researchers found – a generally positive effect. However, the lower temperature on land is likely to weaken sea breezes and alter the mixing of air from different levels of the atmosphere. In turn, these changes will slightly increase PM2.5 concentrations throughout the basin. . . . they found that widespread installation of cool roofs is likely to increase the concentration of ozone in the South Coast Air Basin. This is because UV rays contribute to the formation of ozone.