Travel to any beach in the world, and there's one thing you will probably find-plastic debris. More than ninety-nine million pounds of nonbiodegradable plastic trash is dumped into the ocean from ships, boats, and oil rigs every year. This trash-plastic strapping bands, styrofoam pellets, discarded nylon nets, plastic bags-strangles or drowns countless sea mammals, turtles, and birds.

The causes and consequences of plastic pollution are relatively obvious. More difficult to determine, however, are the environmental effects of other pollutants, such as lead, ozone, carbon monoxide, certain pesticides, and chemical emissions.

The nitrogen, sulphur, and other chemicals emitted into the air by cars and factories react with the moisture in clouds, making rain water mildly acidic. Areas most drastically affected by this acid rain include eastern Europe, Scandinavia, Canada, and the northeastern United States. Acid rain damages crops and forests, erodes the surfaces of buildings, and makes lakes so acidic that they become uninhabitable. Hundreds of once pristine lakes now have such high acid contents that fish and other aquatic species can no longer survive in them.