Air pollution: effects on wild animals

Animals, or wildlife, are vulnerable to harm from air pollution. Pollutant issues of concern include acid rain, heavy metals, persistent organic pollutants (POPs) and other toxic substances.

Insects, worms, clams, fish, birds and mammals, all interact with their environment in different ways. As a result, each animal's exposure and vulnerability to the impacts of air pollution can be equally different.

Air pollution can harm wildlife in two main ways.

• It affects the quality of the environment or habitat in which they live
• It affects the availability and quality of the food supply

How air pollution harms habitat

Habitat is the place in which animals live, including in and on the soil, as well as in water.

Acid rain can change the chemistry and quality of soils and water. For example, water bodies can become too acidic for some animals to survive or have normal physiological functions. Alternatively, acid rain can increase the release of heavy metals, such as aluminum, from soils into water habitats. The result is higher availability of heavy metals in the water column, which are very toxic to many animals including fish.

Some heavy metals, such as mercury, can be transported in the air long distances away from emission sources.

Although not as well understood, other forms of air pollution, such as smog, particulate matter, and ground-level ozone, to mention a few, likely affect wildlife health in similar ways to human health including harming the lungs and cardiovascular systems. An animal's vulnerability to air pollution is influenced by how it breathes - whether it uses lungs, gills or some other form of gas exchange, such as passive diffusion across the surface of the skin.

How air pollution harms food supply and quality

Many heavy metals, toxics, persistent organic pollutants (POPs) and other air pollutants affect wildlife by entering the food chain and damaging the supply and quality of food.

Once consumed, many of these pollutants collect and are stored within the animal's tissues. As animals are eaten by other animals along the food chain, these pollutants continue to collect and increase in concentration. This process is called bioaccumulation. Top level predators such as bears and eagles, among many others, are particularly susceptible to the bioaccumulation of these types of air pollutants.

For example, mercury is of great enough concern that it is recommended we limit how often we eat certain types of fish that may contain high levels of heavy metal.

Air pollutants can poison wildlife through the disruption of endocrine function, organ injury, increased vulnerability to stresses and diseases, lower reproductive success, and possible death.

Changes in the abundance of any species because of air pollution can dramatically influence the abundance and health of dependent species. For example, the loss of some species of fish because of higher levels of aluminum may allow insect populations to increase, which may benefit certain types of ducks that feed on insects. But the same loss of fish could be detrimental to eagles, ospreys and many other animals that depend on fish as a source of food.

It is very difficult to fully understand and appreciate how far and in what ways such changes will affect other species throughout the ecosystem, including humans.