The human population is growing rapidly, and the standard of living is rising. Both mean that more resources are used and more waste is produced. Unless waste and chemical materials are properly handled, more pollution will be caused.
Pollution can occur in three places. In water it can come from sewage, fertiliser or toxic chemicals. In the air it can come from smoke and acidic gases. On land it can come from landfill and from toxic chemicals.
Pollution kills plants and animals. When living things die out in an area, the number of different species falls, so pollution can reduce biodiversity.