Computer simulations for Los Angeles, CA show that resurfacing about two-third of the pavements and rooftops with reflective surfaces and planting three trees per house can cool down Los Angeles by an average of 2–3K. This reduction in air temperature will reduce urban smog exposure in the LA basin by roughly the same amount as removing the basin entire onroad vehicle exhaust. Heat island mitigation is an effective air pollution control strategy, more than paying for itself in cooling energy cost savings. The study estimates that the cooling energy savings in U.S. from cool surfaces and shade trees, when fully implemented, is about $5 billion per year (about $100 per air-conditioned house).

Akbari, Hashem. (2005). Energy Saving Potentials and Air Quality Benefits of Urban Heat Island Mitigation. Lawrence Berkeley National Laboratory: Lawrence Berkeley National Laboratory.