What pollute the earth’s atmosphere naturally? ______and gases from volcanoes po

Sandstorms and dust and gases from volcanoes pollute the earths atmosphere naturally. But the most serious kind of air pollution comes from people. (12) Factories and power stations exhaust harmful gases into the air, contributing to global warming. On a much smaller scale, air pollution causes all sorts of breathing problems. (13) People could reduce air pollution by saving energy and reducing harmful emissions from power stations.
    Air pollution is at its worst over big cities where millions of people live, work and travel about in cars, buses, and trucks. Factory can be fitted with devices to cut down air pollution, but this is expensive. (15) If better public transport and cycle lanes were available in towns and cities, people would be less likely to use their cars, reducing the overall amount of pollution accordingly.