Pollution is a growing concern for our environment, defined as the introduction of a substance or contaminant which has harmful effects on the environment. The main types of pollution are air, water, noise, light, soil, thermal and radioactive, contributors to these are chemical substances (e.g. exhaust fumes and industrial waste) and energy (e.g. street lamps). Pollution has many negative effects on us and the environment, for example respiratory problems in humans, death of marine animals and acid rain. Recycling, renewable energy and compost are a few ways to combat pollution.