Air pollution comes from many different sources such as factories, power plants, dry cleaners, cars, buses, trucks and even windblown dust and wildfires. Air pollution can threaten the health of human beings, trees, lakes, crops, and animals, as well as damage the ozone layer and buildings. Air pollution also can cause haze, reducing visibility in national parks and wilderness areas. EPA protects human health and the environment through the regulatory process and voluntary programs such as Energy Star and Commuter Choice. Under the Clean Air Act, EPA sets limits on how much of a pollutant is allowed in the air anywhere in the United States. Although national air quality has improved over the last 20 years, many challenges remain in protecting public health and the environment. EPA's goal is to have clean air to breathe for this generation and those to follow.

According to the National Academy of Sciences, the Earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities. Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases – primarily carbon dioxide, methane, and nitrous oxide.

Energy from the sun drives the earth’s weather and climate, and heats the earth’s surface; in turn, the earth radiates energy back into space. Atmospheric greenhouse gases (water vapor, carbon dioxide, and other gases) trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse.
Without this natural “greenhouse effect,” temperatures would be much lower than they are now, and life as known today would not be possible. Instead, thanks to greenhouse gases, the earth’s average temperature is a more hospitable 60°F. However, problems may arise when the atmospheric concentration of greenhouse gases increases.

Ozone is a gas that occurs both in the Earth's upper atmosphere and at ground level. Ozone can be "good" or "bad" for people’s health and for the environment, depending on its location in the atmosphere.

In the troposphere, the air closest to the Earth's surface, ground-level or "bad" ozone is a pollutant that is a significant health risk, especially for children with asthma. It also damages crops, trees and other vegetation. It is a main ingredient of urban smog. Motor vehicle exhaust and industrial emissions, gasoline vapors, and chemical solvents as well as natural sources emit NO_x and VOC, that help to form ozone.  Sunlight and hot weather cause ground-level ozone to form in harmful concentrations in the air.  As a result, it is known as a summertime air pollutant.  Many urban areas tend to have high levels of "bad" ozone, but even rural areas are also subject to increased ozone levels because wind carries ozone and pollutants that form it hundreds of miles away from their original sources.

In 1999, recycling and composting activities prevented about 64 million tons of material from ending up in landfills and incinerators. Today, this country recycles 28 percent of its waste, a rate that has almost doubled during the past 15 years. While recycling has grown in general, recycling of specific materials has grown even more drastically: 42 percent of all paper, 40 percent of all plastic soft drink bottles, 55 percent of all aluminum beer and soft drink cans, 57 percent of all steel packaging, and 52 percent of all major appliances are now recycled. Twenty years ago, only one curbside recycling program existed in the United States, which collected several materials at the curb. By 1998, 9,000 curbside programs and 12,000 recyclable drop-off centers had sprouted up across the nation. As of 1999, 480 materials recovery facilities had been established to process the collected materials.

For more information go to
http://www.epa.gov/

They are very keen on encouraging car sharing and use of public transport in England. Emissions tests are done on all uk cars once a year as long as over tests these are all done in an MOT Car Testing it is a legal requirement.

Recycling is highly encouraged all houses are given a separate recycling waste bin which is collected weekly.

London pollution is a big problem you see a lot of cyclists with masks or scarves round their mouths due to all the gases from cars and buses etc.

Air quality has improved since the 1950s, but a variety of pollutants still affect our air, such as carbon monoxide, lead, benzene and 1,3-butadiene, sulphur dioxide and more.

Our use of energy and transport and industrial activity cause emissions to the atmosphere. Environmental impacts can occur locally or at great distances from the emissions.

Ozone in the upper atmosphere shields the earth from harmful ultra violet (UV) radiation emitted by the sun. Man-made chemicals have damaged this “ozone layer”, allowing more UV radiation to pass through.

In England and Wales, six pollution incidents had a major impact on air quality in 2003. Acid rain has been tackled for over a decade with some success.

http://www.envirolink.org/