Lesson 80: Major Air Pollutants and Their Sources
In this lesson, we will learn about the different types of air pollutants. We
will also look at how emissions have declined in the United States since the
Clean Air Act was passed. Finally, we will talk about acid deposition and its
effects.
Primary air pollutants include particulates, volatile organic compounds, carbon
monoxide, nitrogen oxides, sulfur dioxide, lead and air toxics. They are the
direct result of combustion and evaporation. This happens from human industrial
activity and the combustion of fossil fuels primarily.
Secondary air pollutants include ozone, peroxyacetyl nitrates,
sulfuric acid and nitric acid. These occur after primary pollutants undergo
further chemical changes. These air pollutants are created through
photochemical reactions between air pollutants and oxidation of primary air
pollutants by OH radicals.
The EPA tracks pollutants and
measures ambient conditions in air quality throughout the country.
In 2011, emissions were at 99 million tons of primary pollutants. In 1970,
before the Clean Air Act was passed, emissions were at 301 million tons.
Despite increasing domestic activity and more vehicles on the road, air quality
continues to improve over the years.
Acid deposition is precipitation, whether it is rain, fog, mist or snow,
that is more acidic than usual.
Acid precipitation in North America and Europe has been between 10 and 1,000
times more acidic than usual. Acid precipitation is widespread in North
America. It increases primary air pollutants in the air, kills aquatic life and
makes lands toxic with aluminum.
The Clean Air Act has helped reduce acid precipitation as many of the
industrial plants that generate it have had to improve their facilities and
reduce emissions.