This heat influences air circulation and patterns of precipitation. Others emissions such as carbon dioxide, act to trap heat in cities. Cities also release quantities of dust into the atmosphere, with effects like those mentioned next. The dust and emissions released into the atmosphere alter patterns of precipitation over the cities and in areas downwind. Cities often receive more rain than the surrounding countryside since dust can provoke the condensation of water vapor into rain droplets.
Dust carried downwind from cities and industry can increase rain in city shadows.
One of the most notable of these rain shadows, the La Porte anomaly in Indiana, is diagrammed below. Lead- based paint used on roads and highways and on buildings is one such example of a widely dispersed pollutant that found its way into soil. But humans also bury tremendous amounts of waste in the ground at municipal and industrial dumps. These materials can severely contaminate soils. Even such commonplace items like gasoline storage tanks at filling stations have the potential to cause serious contamination.