Air pollution harms animals as a result of direct exposure to contaminants and destruction of their habitats, food and water sources. For instance, acid rain, which forms when pollutants in the atmosphere combine with precipitation, causes aluminum to leach out of the soil, poisoning and often killing fish.
Predators are at particular risk of harm from air pollution due to bioaccumulation, which is the build-up of high concentrations of toxic chemicals that occurs when the animals consume contaminated organisms, including fish, small mammals and plants. Habitat destruction due to changes in soil composition and the destruction of trees caused by acid rain also threatens wildlife in many areas of the world.
Particulate pollution, or the accumulation in the atmosphere of tiny particles of dust and soot, is another direct threat to animal health. One study at Johns Hopkins University showed that an increase of only 20 micrograms of particulate matter per cubic meter of air caused an increase in the human death rate of 1 percent, the National Wildlife Foundation reports. Similar animal studies are lacking, but laboratory experiments show that exposure to the level of dust found in most urban areas causes heart rhythm abnormalities in dogs and harms the heart and lungs of mice and other animals. Scientists also believe that particulate pollution in Africa's drought-stricken Sahel region is threatening coral reefs in many parts of the world. This dust contains bacteria, fungi and viruses, including the fungus Aspergillus that has destroyed 90 percent of Caribbean sea fans since the early 1990s.