Teacher Resource Manual Unit: Air Pollution and Visibility

Georgia’s Air Pollution Problem

(Adapted from www.cleanaircampaign.com, 2005)

Smog is a mixture of air pollutants, some that can be seen or smelled, and others that cannot. In Georgia, the two most important pollutants that threaten human health are ground-level ozone and particle pollution.

Across Georgia, 28 counties or parts of counties are classified by the U.S. EPA as nonattainment areas for either ground-level ozone, particle pollution, or both. This includes 20+ counties in metro Atlanta, as well as areas surrounding Macon, Rome and Chattanooga.

Nonattainment status means that for many days air pollution levels are likely to exceed federal and state limits. Poor air quality poses risks to human health, threatens our economic prosperity, and is detrimental to the environment. Air pollution is a year-round problem in Georgia.

Ground-level ozone, a primary component of smog, is created from a recipe of oxides of nitrogen (NOx) and volatile organic compounds (VOCs or hydrocarbons) cooked by sunlight and high temperatures. It is formed in the atmosphere when days are warm and there is a lot of sunlight. That is why we see more smog in the summer “smog season”, from May 1 – September 30. When combined with particulate matter and other pollutants, smog is formed.
Sources of smog include:

• 
  Nitrogen Oxides (NOx) come almost entirely from man-made sources: combustion of fuels in cars and trucks, coal-fired power plants, industrial boilers and gas-powered engines such as lawnmowers and leaf blowers.
  
• 
  Volatile organic compounds (VOCs) are vapors that emanate from paint and print shops, gas stations, dry cleaners, lawn chemicals, and from combustion engines, such as those in cars and trucks, boats and diesel locomotives. Trees also emit VOCs.
  
• 
  Particle pollution, or particulate matter (PM), consists of a mixture of extremely small solids and liquid droplets that typically includes aerosols and fine solids, such as dust and soot. Sources include all types of combustion, including vehicle exhaust, power plants, wood burning, construction activity and agriculture.
  

(Adapted from www.epa.gov/airnow/aqibroch/aqi.html#2, 2004)

The EPA focuses on six major air pollutants, called criteria pollutants, regulated by the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, lead, and nitrogen dioxide. For each of these pollutants, the Environmental Protection Agency (EPA) has established national air quality standards to protect against harmful health effects.

The AQI for ozone concentrations range from 0 to 500. The higher the AQI value, the greater the level of air pollution and its associated health risks. For example, an AQI value of 50 represents good air quality, while an AQI value higher than 300 represents hazardous air quality.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level the EPA, has established to protect public health. So, AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy—at first for certain sensitive groups of people, then for everyone as the AQI values increase.

The Air Protection Branch of the Georgia Environmental Protection Division is responsible for protecting Georgia’s air quality through the regulation of emissions from industrial and mobile sources. The Ambient Monitoring Program (AMP) maintains a large statewide network of monitors measuring the ambient (outdoor) air for approximately 170 pollutants including ozone, lead, particulate matter, oxides of nitrogen, sulfur dioxide, carbon monoxide, hazardous air pollutants and compounds that aid in smog formation. The program also uses meteorological data to better understand the influence of meteorology on air quality and then reports the air quality index (AQI) for metro Atlanta, Savannah, Columbus, Augusta, the north Georgia mountains, Macon, Brunswick and central Georgia areas. AMP also issues year-round smog alert forecasts for a twenty county area in and around Atlanta.

Air Pollution and Visibility

(Adapted from www.hazecam.net, 2004)
On certain days of the year, when we look at the Atlanta skyline, we do not have a clear view of all of the buildings. A white or brown haze hangs in the air and distorts the view. This haze is unnatural. It is caused by human created air pollution, often carried by the wind hundreds of miles from where it originated. Because of this haze, people in Atlanta are not able to see as far as they normally would if the haze was not present. It is estimated that the typical visual range in the eastern U.S. is 15 to 30 miles, or about one-third of what it would be without human made air pollution.

Haze is caused by fine particles that scatter and absorb light before that light reaches the observer. As the number of fine particles increases, more light is absorbed and scattered, resulting in less clarity, color, and visual range. Five types of fine particles contribute to haze: sulfates, nitrates, organic carbon, elemental carbon, and crustal material. The importance of each type of particle varies across the U.S. and from season to season. Details on each particle type are provided below:

• 
  Sulfate particles form in the air from sulfur dioxide gas. Most of this gas is released from coal-burning power plants and other industrial sources, such as smelters, industrial boilers, and oil refineries. Sulfates are the largest contributor to haze in the eastern U.S. due to the region's large number of coal-fired power plants. In humid environments, sulfate particles grow rapidly to a size that is very efficient at scattering light, thereby exacerbating the problem in the East.
  
• 
  Organic carbon particles are emitted directly into the air and also form there as a reaction of various gaseous hydrocarbons. Sources of direct and indirect organic carbon particles include vehicle exhaust, vehicle refueling, solvent evaporation (e.g., paints), food cooking, and various commercial and industrial sources. Gaseous hydrocarbons are also emitted naturally from trees and from fires, but these sources have only a small effect on overall visibility.
  
• 
  Nitrate particles form in the air from nitrogen oxide gases. These gases are released from virtually all combustion activities, especially those involving cars, trucks, off-road engines (e.g., construction equipment, lawn mowers, and boats), power plants, and other industrial sources. Like sulfates, nitrates scatter more light in humid environments.
  
• 
  Elemental carbon particles are very similar to soot. They are smaller than most other particles and tend to absorb rather than scatter light. The "brown clouds" often seen in urban areas and in mountain valleys can largely be attributed to elemental carbon. These particles are emitted directly into the air from virtually all combustion activities, but are especially prevalent in diesel exhaust and smoke from the burning of wood and wastes.
  
• 
  Crustal material is very similar to dust. It enters the air from dirt roads, fields, and other open spaces as a result of wind, traffic, and other surface activities. Whereas other types of particles come from the condensation and growth of microscopic particles and gasses, crustal material is the result of the crushing and grinding of larger, earth-born material. Because it is difficult to reduce this material to microscopic sizes, crustal material tends to be larger than other particles and falls from the air sooner, contributing less to the overall effect of haze.
  

Some of the pollutants that form haze have been linked to serious health effects and environmental damage. Exposure to fine particles in the air have been linked with increased respiratory illness, decreased lung function, and premature death. In addition, sulfate and nitrate particles contribute to acid rain, which can damage forests, reduce fish populations, and erode buildings, historical monuments, and even car paint.

  To reduce haze we must reduce emissions of haze-forming pollutants across broad areas of the country. Cars, trucks, and industries are much cleaner than they were in the past, and several programs are in place to maintain this progress over the next several years. Nonetheless, these programs by themselves are unlikely to restore visibility to their original pre-haze conditions.

More About Particulate Matter

(Adapted from Georgia Department of Natural Resources, Environmental Protection Division, Air Protection Branch website - www.air.dnr.state.ga.us, 2004)
Particulate Matter (PM) is also known as particle smog. PM is a mixture of solid matter and liquid droplets seen in the air as smoke, dust, soot, fly ash, or condensing vapors. PM can be suspended in the air for long periods of time and is caused by vehicles, power plants, fireplaces, wood stoves, construction projects involving the grinding or crushing of rocks/soil, and unpaved roads. PM represents a broad class of chemically diverse particles that range in size from molecular clusters of 0.005 micrometers (µm) to coarse particles of 50-100 µm in diameter (70 µm is about the thickness of an average human hair). PM results from all types of combustion. The carbon-based particles that result from incomplete burning of diesel fuel in buses, trucks and cars are of particular concern. Another important combustion source is the burning of wood in stoves and fireplaces in residential settings. Also of concern are the sulfate and nitrate particles that are formed as a byproduct of SO₂ and NO₂ emissions, primarily from fossil fuel-burning power plants and vehicular exhausts.
According to the Environmental Protection Agency (EPA), particles smaller than 10 µm, termed PM10, cause most of the adverse health effects. PM10 particles have the ability to penetrate deeply into the lungs. The observed human health effects of particulate matter include respiratory symptoms, aggravation of existing respiratory and cardiovascular disease, and alterations in the body's defense system against inhaled materials and organisms, and damage to lung tissue. Groups that appear to be most sensitive to the effects of particulate matter include individuals with chronic lung or cardiovascular disease, individuals with influenza, asthmatics, elderly people, and children.
Fine Particles (PM_2.5) Questions and Answers
What is Particulate Matter 2.5 (PM_2.5)?
The term “fine particles,” or “particulate matter 2.5” refers to tiny particles or droplets in the air that are two and one-half microns or less in width. Like inches, meters, and miles, a micron is a unit of measurement for distance. There are about 25,000 microns in an inch. The widths of the larger particles in the PM_2.5 size range would be about thirty times smaller that that of a human hair. The smaller particles are so small that several thousand of them could fit on the period at the end of this sentence.
How can PM_2.5 affect my health?
Particles in the PM_2.5 size range are able to travel deeply into the respiratory tract, reaching the lungs. Exposure to fine particles can cause short-term health effects such as eye, nose, throat and lung irritation, coughing, sneezing, runny nose, and shortness of breath. Exposure to fine particles can also affect lung function and worsen medical conditions such as asthma and heart disease. Scientific studies have linked increases in daily PM_2.5 exposure with increased respiratory and cardiovascular hospital admissions, emergency room visits, and deaths. Recent studies suggest that long-term exposure to particulate matter may be associated with increased rates of bronchitis and reduced lung function. People with breathing and heart problems, children, and the elderly may be particularly sensitive to PM_2.5.
Where does PM_2.5 come from?
There are outdoor and indoor sources of fine particles. Outside, fine particles primarily come from power plants, and exhaust from cars, trucks, busses, and off-road vehicles (e.g. construction equipment, snowmobiles, locomotives). Fine particulates also come from other operations that involve the burning of fuel or vegetation. Fine particles also form from the reaction of gases or droplets in the atmosphere. These chemical reactions can occur miles from the original source of the emissions. In Georgia, some of the fine particles measured in the air are carried by wind from out-of-state sources. Because fine particles can be carried long distances from their source, events such as wildfires or volcanic eruptions can raise fine particle concentrations hundreds of miles from the event.
PM_2.5 is also produced by common indoor activities. Some indoor sources of fine particles are tobacco smoke, cooking (e.g. frying, sautéing and broiling), burning candles or oil lamps, and operating fireplaces and fuel-burning space heaters (e.g. kerosene heaters).
Is there an air quality standard for PM_2.5 in outdoor air?
Yes. The United States Environmental Protection Agency (EPA) established National Ambient Air Quality Standards for PM_2.5 in 1997. National Ambient Air Standards are established for the protection of public health. The short-term standard (24-hour or daily average) is 65 micrograms per cubic meter of air and the long-term standard (annual average) is 15 micrograms per cubic meter. A microgram is a unit of weight. There are a million micrograms in a gram, and a pound is equal to about 450 grams.
How will I know when PM_2.5 levels are, or will be, elevated outside?
Outdoor air levels of fine particles increase during periods when air is stagnant (i.e. when there is very little wind and air mixing), when the particles are not carried away by wind, or when winds bring polluted air into the state from sources outside the state. In general, as the levels of PM_2.5 in outdoor air increase, the air appears hazy and visibility is reduced. These conditions are similar in appearance to high humidity or fog. PM_2.5 forecasts may also appear on newscasts and in newspapers. The EPA’s AIRNOW website (www.epa.gov/airnow) has information on air quality for Georgia and for the rest of the nation.
Are there ways to reduce my exposure to PM_2.5?
When outdoor levels of PM_2.5 are elevated, going indoors may reduce your exposure, although some outdoor particles will come indoors. If there are significant indoor sources of PM_2.5, levels inside may not be lower than outside. Some ways to reduce exposure are to limit indoor and outdoor activities that produce fine particles (for example, the burning of candles indoors or open burning outdoors) and to avoid strenuous activity in areas where fine particle levels are high.
Note about pollen: The dust-like particles on the anthers of a flower are pollen grains. While pollen is an airborne allergen, it is not considered a type of particulate matter. For more information about pollen, log onto the National Institutes of Allergy and Infectious Diseases – National Institutes of Health website (www.niaid.nih.gov/newsroom/focuson/allergy99/allergyspot.htm) or the National Allergy Bureau (www.aaaai.org/nab/).

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