Finally, excessive crop spraying with pesticides is also a cause of air pollution. Pesticides are poisonous chemicals, and although they can be carried to anywhere by wind to kill pests, they harm to plants and animals at the same time. These poisonous chemicals concentrate in food by plants; therefore they usually have bad effects on health of human beings.
To sum up, there are various causes of air pollution, with serious effects on human beings' health. Though it is difficult to avoid, it may be decreased by people's effort.
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