Pollution - Environmental Science - page 150

Chapter 6: Pollution
The wide variety of human activities on the planet is accompanied by the unintended consequences of environ-
mental pollution. Air, water, and soil all can become polluted. With an ever-increasing number of people being
added to the planet, noise, light, and genetic pollution are becoming more common as well. Pollution can harm
wildlife, ecosystems, and humans, and its presence requires efforts to reduce and eliminate it.
Pollution Types
Pollution comes in various forms and can adversely affect the biosphere's land, atmosphere, and water. Though
the sources of pollution and the areas it affects are many, pollution is categorized two ways: point-source pol-
lution or non-point-source pollution. Point-source pollution is emitted from a specific place, such as
wastewater from a plant, acid drainage from a mine, noise from a jet plane, or oil from a tank. Identifying the
main source of non-point-source pollution can be difficult, because it may come from a multitude of smaller
sources. Examples of non-point-source pollution include emissions from vehicles, runoff from a group of
farms, and emissions from widely dispersed factories.
Air, water, and soil are forms of pollution but are accompanied by noise, light, and genetic pollution as well.
Measuring units
To express pollutant amounts present in air, in water, on land, and in tissue, the term parts per million
(ppm) is commonly used. Ppm is the concentration of a very dilute toxin or substance in relative propor-
tion to another substance (in this case, meaning one part per million). For example, 2 ppm chlorine corres-
ponds to 2 parts chlorine to 1,000,000 parts water. Parts per billion (ppb) and parts per trillion (ppt) also
are used as measurements of concentration.
Air Pollution
Human-caused air pollution has been a problem since the Industrial Revolution, when combustion of fossil
fuels became the world's primary source of energy. Air pollution is composed of unwanted gases and particu-
late matter and can be created through natural means or through human actions. Natural polluting events in-
clude wildfires, wind-blown debris and dust storms, and volcanic activity.
Airborne chemicals can travel far, so even though a pollutant is emitted from one source, it can affect an eco-
system hundreds or thousands of miles away, potentially in countries other than its source.
Major Air Pollutants
Six common air pollutants monitored by the Environmental Protection Agency (EPA) are considered to be cri-
teria pollutants and are measured to gauge air quality. These criteria pollutants are carbon monoxide, nitrogen
dioxide, sulfur dioxide, ozone, lead, and particulate matter.
Carbon monoxide (CO) is a colorless, odorless gas that results from the incomplete combustion of organic
matter, especially fossil fuels. The use of fossil fuels in the internal combustion engines of vehicles accounts
for the majority of CO emissions. Boats, lawn mowers, and construction equipment also contribute large