1. CHAPTER 12.1 ENVIRONMENTAL SCIENCE What Causes Air Pollution?

2.  In most places in the United States the air is fairly clean. In other parts of the world, like India and Bangladesh the air is so polluted it harms peoples health.  Clean air consists of mostly nitrogen and oxygen, with very small amounts of argon, carbon dioxide, and water vapor.  Air pollution is when harmful substances are at unhealthy levels in the air.  Most air pollution is caused by human activity. There are natural pollutants like when a volcano erupts, also dust, spores, and pollen in the air.

3. PRIMARY AND SECONDARY POLLUTANTS  A primary pollutant is pollution that is put in the air by human activity.  An examples is soot from smoke.  Secondary pollutants are when primary pollutants react with other primary pollutants or naturally occurring substances.  An example is ground-level ozone. This forms when uv rays cause automobile emissions to react with oxygen in the atmosphere.

4. SOURCES OF PRIMARY AIR POLLUTANTS  Many household products, power plants, and automobiles are sources of primary air pollution like carbon monoxide, nitrogen oxide, sulfur dioxide, and chemicals called volatile organic compounds.  Particulate matter can also pollute the air. There are 2 types of particulate matter – fine and coarse particles.  Fine particles enter the air from fuel burned by vehicles and coal-burning power plants.  Coarse particles are made from cement plants, mining operations, incinerators, wood-burning fireplaces, field, and roads.

5. THE HISTORY OF AIR POLLUTION  Air pollution is not a new idea – whenever you burn something pollutants enter the air.  The problem is the air-quality is much worse because of the amount of fossil fuels that are burned.

6. MOTOR VEHICLE EMISSIONS  1/3 of our air pollution comes from gasoline burned by vehicles.  The Clean Air Act passed in 1970 (revised in 1990). It gives the EPA (Environmental Protection Agency) the authority to regulate vehicle emissions.  The first thing it did was eliminate lead used in gasoline. This has reduce the amount of lead pollution 90%.  Also catalytic converters are used on vehicles to clean the exhaust coming from cars.

7. CALIFORNIA ZERO-EMISSION VEHICLE PROGRAM  To improve air quality in California the states Air Resources Board made the Zero Emission (ZEV) program in 1990. These vehicles have no tailpipe emissions, no emissions from gasoline, and no emission-control system.  Battery power electric vehicle are the only true ZEVs. There are 3 types of partial ZEVs: one is clean, fuel-efficient hybrid cars (powered by both batter and gasoline engines), another is a hydrogen- powered car that emits only water vapor. There are also hybrid cars that required being plugged in.

8. INDUSTRIAL AIR POLLUTION  Many industries and power plants burn fuel to produce energy. Mostly they burn fossil fuels. This release sulfur dioxide and nitrogen oxides into the air.  Other industries like dry cleaning produce VOCs.

9. REGULATING AIR POLLUTION FROM INDUSTRY  The Clean Air Act requires many industries to use scrubbers or other pollution-control devices.  Many cement factories and coal- burning power plants use electrostatic precipitators to remove dust particles from smoke stacks.

10. SMOG  Smog is when air pollution hangs over an area and reduces visibility.  This usually happens from a reaction between sunlight, air, automobile exhaust, and ozone.  Industries and vehicles are the main sources of smog.

11. TEMPERATURE INVERSIONS  Most of the time circulation of air in the atmosphere keeps air pollution from reaching dangerous levels.  Sometimes air pollution gets stuck near the Earth’s surface.  A temperature inversion is when air above is warmer than the air below. Usually air temperature decreases with altitude. This inversion traps air near Earth’s surface.  A city in a valley has a greater chance of experiencing an temperature inversion. This is why Los Angeles has a lot of smog. It gets trapped in that area.