The document discusses air pollution, defining it as contamination of the air indoors or outside. It can be caused by harmful gases, dust, or smoke entering the atmosphere. Air pollution can harm plants, animals, and humans by making air dirty and difficult to breathe. It is classified into visible and invisible types and can be caused by both natural sources like volcanoes and human activities like burning fossil fuels. Major effects of air pollution include respiratory illnesses and heart disease in humans as well as damage to materials and negative impacts on wildlife habitats and health.