In my previous article titled "Causes and Effects of Indoor Air Pollution," I primarily talked about indoor pollution, its causes and effects and did not focus much on outdoor pollution. Outdoor air pollution is the type of air pollution we are used to, like smog, sulfur dioxide, carbon monoxide, and lead. These chemicals can have dangerous effects on our health as humans, but they can also cause damage to the environment which makes the resources we use, like food and water, dangerous to consume.
One example of that is acid rain, rain that contains harmful amounts of nitric and sulfuric acids. These acids are formed by the nitrogen oxides and sulfur oxides that are released into the atmosphere when fossil fuels are burned. As always, what goes up must come down and these acids fall to the Earth either as wet precipitation (rain, snow, or fog) or dry precipitation (gas and particulates). Acid rain damages trees and causes soils and water bodies to acidify, making the water unsuitable for fish and other wildlife. It also speeds the decay of buildings, statues, and sculptures.
If a body of water has a high concentration of nutrients (like nitrogen) that stimulates the growth of algae it is called eutrophication. It can cause fish kills and loss of plant and animal diversity. Although eutrophication is a natural process in the aging of lakes and some estuaries, human activities can greatly accelerate eutrophication by increasing the rate at which nutrients enter aquatic ecosystems. Air emissions of nitrogen oxides from power plants, cars, trucks, and other sources contribute to the amount of nitrogen entering aquatic ecosystems.
A familiar effect of air pollution is haze. Haze is caused when sunlight encounters tiny pollution particles in the air. It obscures the clarity, color, texture, and form of what we see. Some haze-causing pollutants (mostly fine particles) are directly emitted to the atmosphere by sources such as power plants, industrial facilities, trucks and automobiles, and construction activities. Others are formed when gases emitted to the air (such as sulfur dioxide and nitrogen oxides) form particles as they are carried downwards.
Toxic pollutants in the air, or deposited on soils or surface waters, can impact wildlife in a number of ways. Like humans, animals can experience health problems if they are exposed to sufficient concentrations of air toxins over time. Studies show that air toxins are contributing to birth defects, reproductive failure, and disease in animals. Persistent toxic air pollutants (those that break down slowly in the environment) are of particular concern in aquatic ecosystems. These pollutants accumulate in sediments and may become more apparent in tissues of animals at the top of the food chain to concentrations many times higher than in the water or air because they have been consistently consuming the pollutants.
Another effect air pollution has on the environment is ozone depletion. Ozone is a gas that occurs both at ground-level and in the Earth's upper atmosphere, a.k.a. the stratosphere. At ground level, ozone is a pollutant that can harm human health. In the stratosphere, however, ozone forms a layer that protects life on earth from the sun's harmful ultraviolet (UV) rays. But this "good" ozone is gradually being destroyed by man-made chemicals referred to as ozone-depleting substances, including chlorofluorocarbons, hydro-chlorofluorocarbons, and halons. These substances were formerly used and sometimes still are used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants. Thinning of the protective ozone layer can cause increased amounts of UV radiation to reach the Earth, which can lead to more cases of skin cancer, cataracts, and impaired immune systems. UV can also damage sensitive crops, such as soybeans, and reduce crop yields.
Speaking of damage to food, air pollution can also damage crops and trees in a variety of other ways. Ground-level ozone can lead to reductions in agricultural crop and commercial forest yields, reduced growth and survival rate of tree seedlings, and increased plant susceptibility to disease, pests and other environmental stresses (such as harsh weather). As described above, crop and forest damage can also result from acid rain and from increased UV radiation caused by ozone depletion.
The most concerning effect of air pollution on the environment is global climate change. The Earth's atmosphere contains a delicate balance of naturally occurring gases that trap some of the sun's heat near the Earth's surface. This "greenhouse effect" keeps the Earth's temperature stable. Unfortunately, evidence is increasingly showing that humans have disturbed this natural balance by producing large amounts of some of these greenhouse gases, including carbon dioxide and methane. As a result, the Earth's atmosphere appears to be trapping more of the sun's heat, causing the Earth's average temperature to rise - a phenomenon known as global warming. Many scientists believe that global warming could have significant impacts on human health, agriculture, water resources, forests, wildlife, and coastal areas. Click on the photo to learn more about the social and economic impacts of climate change.