Pollution — a consequence of waste products being improperly managed and natural resources being unsustainably consumed — affects the air we breathe, the water we drink, and the soil where we grow food. It causes a variety of health issues, harms the natural environment, and lessens our quality of life.
People generally classify pollution according to the pathway by which it is distributed — either air, land, or water pollution. In reality, pollutants often affect two or even all three pathways. For example, a plastic bag littered on a road can start as land pollution, be blown by the wind, and wash into a stream, emitting toxic chemicals along the way.
Air pollution comes from many different sources, and can contaminate indoor air in homes and buildings, or air in the atmosphere. Pollutants may be natural or human-made and may consist of solid particles, liquid droplets, or gases. The U.S. Environmental Protection Agency (EPA) monitors over 188 toxic chemicals that can pollute the air.
The air pollutant that may threaten Earth's sustainability the most is actually a natural component of air. Carbon dioxide is necessary for photosynthesis, the process plants use to create food. But, since 1750, the amount of carbon dioxide in the atmosphere has increased 30 percent, a rise that is contributing to climate change. Coal-fired power plants are the largest source of carbon dioxide pollution in the U.S., creating 2.5 billion tons each year, while automobiles produce almost 1.5 billion tons.
Land pollution includes contamination of the soil itself as well as waste and litter. Soil contamination is mainly due to chemicals in weed killers and pesticides, but may also be from other sources like lead-based paints or the past use of leaded gasoline. Waste and litter are not only unsightly and dirty, they can also threaten health by harboring pests and disease. Poor agricultural or mining practices, the dumping of industrial waste, and inadequate urban waste disposal can all cause land pollution.
Water pollution affects both fresh and ocean waters and may include any number of substances from soil particles to pesticide residues to heavy metals. Some pollution — such as industrial water discharge and sewage disposal lines — is introduced directly into the water. But most water pollution comes from "nonpoint" or indirect sources, such as runoff from farms, construction sites, or streets.
Whatever form it takes, pollution is largely a consequence of waste products being improperly managed and natural resources being unsustainably consumed. When nature is our teacher, we learn that waste from one species is another species' food in a healthy ecosystem. We discover that there are limits to nature's ability to maintain ecosystems that are conducive to life. Exceeding those limits hurts our ability to obtain clean water and air and healthful food, and also harms other life forms.
Schooling for sustainability includes adopting practices that minimize the pollution that the school discharges into the environment, in areas ranging from transportation policy to pest management and the use of chemicals in laboratories.