Sandstorms and the dust and gases from volcanoes pollute the earth's atmosphere naturally. But the most serious kind of air pollution comes from people. Factories, power stations, and rehicles exhausts pump harmful gases into the air, contributing to global warming, causing acid rain, and destroying the ozone layer. On a much smaller scale, air pollution causes all sorts of breathing problems. There are no simple solutions to air pollution, but people could reduce air pollution by saving energy and reducing harmful emissions from vehicle exhausts and power stations.
When a volcano erupts, dust is blasted high above the troposphere and may take weeks to be carried around the weather zone, so cannot be washed out of the air by rain. It will eventually fall to the earth after a few years.
Air pollution is at its worst over big cities where millions of people live, work, and travel about in cars, buses, and trucks. Factory chimmeys can be fitted with devices to cut down air pollution, but this is expensive. If better pubic 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.
Smoking cigarettes adds to the general levels of air pollution as well as damaging our health. Cigarette smoke contains chemicals that can cause cancer, a gas which stops oxygen being taken into the blood and a substance called nicotine, which raises blood pressure and makes the heart beat faster. No-smoking areas cut down on this pollution and save non-smokers breathing in other people's cigarette smoke.