The EPA Office of Air Quality Planning and Standards (OAQPS) has set National Ambient Air Quality Standards for six principal pollutants, which are called "criteria" pollutants". These are Carbon Monoxide (CO), Nitrogen dioxide (NO2), Ozone (O3), Lead (Pb), Particulate matter with a size of 10 micrometers (PM-10), Particulate matter with a size of 2.5 micrometers (PM-2.5), and sulfur dioxide (SO2). "Units of measure for the standards are parts per million (ppm), milligrams per cubic meter of air (mg/m3), and micrograms per cubic meter of air (µg/m3)."
Ground-level ozone is produced by the combination of pollutants from many sources, including smokestacks, cars, paints and solvents. When a car burns gasoline, releasing exhaust fumes, or a painter paints a house, smog-forming pollutants rise into the sky.
Often, wind blows smog-forming pollutants away from their sources. The smog-forming reactions take place while the pollutants are being blown through the air by the wind. This explains why smog is often more severe miles away from the source of smog-forming pollutants than it is at the source.
The smog-forming pollutants literally cook in the sky, and if it's hot and sunny, smog forms more easily. Just as it takes time to bake a cake, it takes time to cook up smog-several hours from the time pollutants get into the air until the smog gets really bad.
Weather and geography determine where smog goes and how bad it is. When temperature inversions occur (warm air stays near the ground instead of rising) and winds are calm, smog may stay in place for days at a time. As traffic and other sources add more pollutants to the air. the smog gets worse.
Since smog travels across county and state lines, when a metropolitan area covers more than one state (for instance, the New York metropolitan area includes parts of New Jersey and Connecticut), their governments and air pollution control agencies must cooperate to solve their problem. Governments on the East Coast from Maine to Washington, D.C., will have to work together in a multistate effort to reduce the area's smog problem.
Photo was taken from EPA website
The 1990 Clean Air Act uses this new classification system to tailor clean-up requirements to the severity of the pollution and set realistic deadlines for reaching clean-up goals. If deadlines are missed, the law allows more time to clean up, but usually a nonattainment area that has missed a clean-up deadline will have to meet the stricter clean-up requirements set for more polluted areas.
Not only must nonattainment areas meet deadlines, states with nonattainment areas must show EPA that they are moving on clean-up before the deadline-making reasonable further progress.
States will usually do most of the planning for cleaning up criteria air pollutants, using the permit system to make sure power plants, factories and other pollution sources meet their clean-up goals.
The comprehensive approach to reducing criteria air pollutants taken by the 1990 Act covers many different sources and a variety of clean-up methods. Many of the smog clean-up requirements involve motor vehicles (cars, trucks, buses). Also, as the pollution gets worse, pollution controls are required for smaller sources.
Despite this progress, most types of air pollution from mobile sources have not improved significantly.
At present the United States:
Many people live far from where they work; in many areas, buses, subways, and commuter trains are not available. Also, most people still drive to work alone, even when van pools, HOV (high-occupancy vehicle) lands and other alternatives to one-person-per-car commuting are available.
Buses and trucks, which produce a lot of pollution, haven't had to clean up their engines and exhaust systems as much as cars.
Auto fuel has become more polluting. As lead was being phased out, gasoline refiners changed gasoline formulas to make up for octane loss, and the changes made gasoline more likely to release smog-forming VOC vapors into the air.
Although cars have had pollution control devices since the 1970s, the devices only had to work for 50,000 miles, while a car in the United States is usually driven for 100,000 miles.
The information listed above was taken from the EPA's The Plain English Guide To The Clean Air Act
An update on the 1996 modifications to the Clean Air Act which place stricter regulations on particulate matter and ozone can be found at EPA links under the side header New Air Rules
EPA's Office of Air and Radiation (OAR) Air Pollution EPA Office of Air and Radiation Includes information on the Ozone layer, urban air, air toxics, vehicles/engines, indoor air, visibility, acid rain, radiation, and prevention
You can view regional air qualtity trends at the EPA's AIRS System for visually exploring& presenting airs data AIRS graphic systems or find Real-Time air pollution data for some states (not KS or MO) at Real Time Air Pollution Data
You can find Air Pollution links or other interesting atmospheric information by selecting "links" from the "Our Changing Atmosphere" homepage of the University of Michigan AOSS/Chem 105 home page by clinking here Pollution Links
British Columbia Ministry of Environment, Land & Parks Environmental Protection has air pollution and smog information entitled "No Room to Breathe: Photochemical Smog and Ground-Level Ozone" August, 1992 Photochemical smog-info
EPA refers to chemicals that cause serious health and environmental hazards as hazardous air pollutants (HAPs) or air toxics.
The toxic air pollutants of greatest concern are those that cause serious health problems or affect many people. Health problems can include cancer, respiratory irritation, nervous system problems, and birth defects.
Air toxics are released from sources throughout the country and from motor vehicles. For example, gasoline contains toxic chemicals. Gases escape from liquid gasoline and form a vapor in a process called vaporization or evaporation. When you put gas in your car, you can often see wavy lines in the air at the pump nozzle and you can smell gasoline; that tells you gasoline vapors are in the air.
When cars and trucks burn gasoline, air toxics come out of the tailpipes. (These air toxics are combustion products--chemicals that are produced when a substance is burned.)
Air toxics are released from small stationary sources, such as dry cleaners and auto paint shops Large stationary sources, such as chemical factories and incinerators, also release hazardous air pollutants. The 1990 Clean Air Act deals more strictly with large sources than small ones, but EPA must regulate small sources of hazardous air pollutants as well.
To reduce air toxics pollution, EPA must first identify the toxic pollutants whose release should be reduced. The 1970 Clean Air Act gave EPA authority to list air toxics for regulation and then to regulate the chemicals. The agency listed and regulated seven chemicals through 1990. The 1990 Act includes a list of 189 hazardous air pollutants selected by Congress on the basis of potential health and/or environmental hazard; EPA must regulate these listed air toxics. The 1990 Act allows EPA to add new chemicals to the list as necessary.
To regulate hazardous air pollutants, EPA must identify categories of sources that release the 189 chemicals listed by Congress in the 1990 Clean Air Act. Categories could be gasoline service stations, electrical repair shops, coal-burning power plants, chemical plants, etc. The air toxics producers are to be identified as major (large) or area (small) sources.
Once the categories of sources are listed, EPA will issue regulations. In some cases, EPA may have to specify exactly how to reduce pollutant releases, but wherever possible companies will have flexibility to choose how they meet requirements. Sources are to use Maximum Available Control Technology (MACT) to reduce pollutant releases; this is a very high level of pollution control.
EPA must issue regulations for major sources first, and must then issue regulations to reduce pollution from small sources, setting priorities for which small sources to tackle first, based on health and environmental hazards, production volume, etc.
If a company wishes to increase the amount of air toxics coming out of an operating plant, the company may choose to offset the increases so that total hazardous air pollutant releases from the plant do not go up. Otherwise, they may choose to install pollution controls to keep pollutants at the required level.
If a company reduces its releases of a hazardous air pollutant by about 90 percent before EPA regulates the chemical, the company will get extra time to finish cleaning up the remaining 10 percent. This early reduction program is expected to result in a speedy reduction of the levels of several important hazardous air pollutants.
Under the 1990 Clean Air Act, EPA is required to study whether and how to reduce hazardous air pollutants from small neighborhood polluters such as auto paint shops, print shops, etc. The agency will also have to look at air toxics pollution after the first round of regulations to see whether the remaining health hazards require further regulatory action.
Cars, trucks, buses and other mobile sources release large amounts of hazardous air pollutants like formaldehyde and benzene. Cleaner fuels and engines and making sure that pollution control devices work should reduce hazardous air pollutants from mobile sources.
The Bhopal tragedy inspired the 1990 Clean Air Act requirement that factories and other businesses develop plans to prevent accidental releases of highly toxic chemicals. The Act establishes the Chemical Safety Board to investigate and report on accidental releases of hazardous air pollutants from industrial plants. The Chemical Safety Board will operate like the National Transportation Safety Board (NTSB), which investigates plane and train crashes.
Source of image: Smogbusters homepage, Canberra, Australia Air Pollution Fact Sheet
Air pollutants can also harm plants by reducing photosynthesis, damage leaves, and leading to lower plant productivity.
You can find out more information about the EPA's acid rain program, the emissions reduction and trading allowances in the U.S., and the environmental effects of Acid Rain at EPA Acid Rain Program
Source of image: EPA-Acid Rain-Student Page You can also find a map of the 1996 pH level of rain across the U.S.on the EPAs Acid Rain Student Page.
A pH greater than 7 is basic. Each whole pH value below 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6. The same holds true for pH values above 7, each of which is ten times more alkaline (another way to say basic) than the next lower whole value. For example, pH 10 is ten times more alkaline than pH 9 and 100 times (10 times 10) more alkaline than pH 8.
The U.S. Geological Survey is the lead government agency monitoring atmospheric deposition in the U.S. Data, reports and information from the acid rain monitoring program can be found at the U.S.G.S. Acid rain homepage
In depth text on Acid Deposition is found at American Meterological Society-Acid Depoisition
A brief description of Acid rain is found at National Geographic-Acid Rain
setting National Air Quality Standards (NAAQS) for pollutants considered harmful to the public health and environment ensuring the air quality standards are met or attained (in cooperation with the States) through national standards and strategies to control air emission standards from sources ensuring the sources of toxic air pollutants are well controlled monitoring the effectiveness of the program.
One way to protect and assess air quality was through the development of an Ambient Air Monitoring Program. Air quality samples are generally collected for one or more of the following purposes:
To judge compliance with and/or progress made towards meeting ambient air quality standards. To activate emergency control procedures that prevent or alleviate air pollution episodes. To observe pollution trends throughout the region, including non-urban areas. To provide a data base for research evaluation of effects: urban, land-use, and transportation planning; development and evaluation of abatement strategies; and development and validation of diffusion models.
With the end use of the air quality samples as a prime consideration, the network should be designed to meet one of four basic monitoring objectives listed below:
1.To determine highest concentrations expected to occur in the area covered by the network;
2.to determine representative concentrations in areas of high population density;
3.to determine the impact on ambient pollution levels of significant sources or source categories; and
4.to determine general background concentration levels.
The SLAMS consist of a network of ~ 4,000 monitoring stations whose size and distribution is largely determined by the needs of State and local air pollution control agencies to meet their respective State implementation plan (SIP) requirements.
The NAMS (1,080 stations) are a subset of the SLAMS network with emphasis being given to urban and multi-source areas. In effect, they are key sites under SLAMS, with emphasis on areas of maximum concentrations and high population density.
A PAMS network is required in each ozone nonattainment area that is designated serious, severe, or extreme. The required networks will have from two to five sites, depending on the population of the area. There will be a phase-in period of one site per year starting in 1994. The ultimate PAMS network could exceed 90 sites at the end of the 5-year phase-in period.
The SLAMS, NAMS and PAMS monitoring sites were taken from
The EPA's The
Ambient Air Monitoring Program Site