Air Laboratory Section

The Air Laboratory of the Environmental Preservation and Technical Services Division is responsible for monitoring air quality throughout the state. The laboratory maintains five acid precipitation samplers in the State. It also does continuous air monitoring for ozone, sulfur dioxide, carbon monoxide, and oxides of nitrogen at six locations in Arkansas. PM-10 and PM-2.5 samplers also collect particulate samples around the state.

Air Laboratory personnel collect the Air Quality Index (AQI)* each weekday.

The AQI* is a measure of the following five major atmospheric pollutants:

• Carbon monoxide (CO)
• Nitrogen dioxide (NO₂)
• Ozone (O₃)
• Sulfur dioxide (SO₂)
• Particulates (PM-10 and PM-2.5)

The computer does a calculation to detect the highest contributor of these five pollutants. The index is based upon the highest contributing pollutant. For example, if ozone is highest, then the value for ozone determines the index.

• Air Quality Index (AQI) - Little Rock *.
• Air Quality Index (AQI) - Springdale *.

AQI values range from zero (good air quality) to 500 (significantly harmful) with varying levels determining the potential adverse effects of the air quality. An AQI of 100 means that the air quality is meeting the National Ambient Air Quality Standards (NAAQS) established by the U.S. EPA. Anything below 100 shows that pollutants are below the levels established for NAAQS. A value above 100 shows that at least one pollutant is exceeding the NAAQS. The table below, based on requirements defined in 40 CFR Part 58, outlines the levels, health effects descriptions, general health effects, and cautionary statements of AQI values.

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Listing And Description Of The Five Major Atmospheric Pollutants

Carbon Monoxide (CO)

Carbon monoxide is a byproduct of combustion of fossil fuels. Gasoline-powered motor vehicles, forest fires, structural fires, and other fires produce it. It is a colorless, odorless, but extremely toxic gas formed by incomplete combustion of fuels.

A continuous monitor monitors carbon monoxide in the environment. It takes readings every eight hours. We report the levels in parts per million (ppm). Carbon monoxide levels above 9.0 ppm exceed the NAAQS.

Health and other effects of CO in the atmosphere

• Slows reactions and impairs judgment.
• Disables the central nervous system.
• Impairs vision.
• Produces headaches, dizziness, and nausea.
• Exerts strain on the heart.

In your home, faulty, gas-burning appliances can give off carbon monoxide. It can build up to levels that can cause death. Please have a licensed heating and air-conditioning service check your heater, water heater, and other gas-burning appliances if you experience any of the above symptoms. Just to be safe, you should have your appliances checked periodically. Carbon monoxide alarms, similar to smoke detectors, are available from many hardware and discount stores. If you are concerned about carbon monoxide in your home, purchase a CO detector.

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Nitrogen dioxide (NO₂)

Nitrogen oxides are formed from high temperature combustion. They are primarily produced by gasoline-powered motor vehicles and coal-burning industries like electric power plants. Nitrogen dioxide is not only a health danger, but is also a prime ingredient in the formation of both acid rain and smog.

We measure nitrogen dioxide in parts per million (ppm) by a continuous monitor. The samplers take readings at hourly intervals. EPA's health-based national air quality standard for NO₂ is 0.053 ppm, measured as an annual arithmetic mean concentration. (See U.S. EPA 1998 National Air Quality: Status and Trends, Six Principle Pollutants).

Health and other effects of NO₂

• Irritate eyes and nose
• Increase susceptibility to influenza.
• Cause visible leaf damage and stunt plant growth.
• Create brown haze.
• Corrode metals.

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Ozone (O₃)

Ozone is a reactive form of oxygen. It is the prime ingredient of smog in our cities. While no one emits ozone directly into the air, it is formed by gases called nitrogen oxides and volatile organic compounds (VOCs). When these compounds react with heat and sunlight, it forms ozone. Ground-level ozone forms readily in the atmosphere, especially during hot weather. Nitrogen oxides are emitted from motor vehicles, power plants, and other sources of combustion. VOCs are given off from many sources including: motor vehicles, chemical plants, oil refineries, factories, and consumer and commercial products. Ozone concentrations can vary from year to year due to changing weather patterns. Ozone and the compounds that cause it can travel hundreds of miles from the pollution source. Even at low levels, ozone can cause problems if inhaled.

A continuous monitor measures ozone hourly. We report it as parts per million (ppm). The air quality standard for ozone is 0.08 ppm. The Arkansas Department of Health and Arkansas Department of Environmental Quality issue an Ozone Health Advisory if an eight-hour average of hourly readings exceeds this level. People at risk during an ozone advisory are those with breathing problems, such as asthma; those who are active outdoors, such as children and construction workers.

Health and other effects of O₃

• Acute respiratory problems
• Aggravate asthma.
• Decrease lung capacity by 15 to 20 percent, even in health adults.
• Impair the body's immune system, making people more susceptible to respiratory illness, such as bronchitis and pneumonia.
• Interfere with the ability of plants to photosynthesize food and store the food impairing growth, reproduction and plant health overall.
• Weaken sensitive vegetation making it more susceptible to pests, disease, and other environmental stresses.
• Reduce yields of agricultural, economically important crops like soybeans, wheat, and cotton.
• Other effects of long-term ozone problems include adverse impacts to complete ecosystems like forests; damage to leaves so that they diminish natural beauty of trees in parks and recreation areas; and possibly, even fish kills and algal blooms in sensitive waterways.

If they issue an ozone health advisory, there are steps that the public can take to help reduce ozone levels.

• Use public transit, car pool, or walk.
• Postpone or avoid painting and use of aerosol products, varnishes, and degreasers.
• Postpone use of gasoline-powered yard and garden equipment until late afternoon.
• Reduce rush hour traffic through flextime and telecommuting.
• Combine auto trips during the day.
• Postpone putting gas in your vehicle(s) until after 6:00 p.m.
• Avoid driving at lunch time.
• Postpone errands that require starting your car until later in the day.

To get more information on ozone and what is being done about it in Little Rock and the surrounding area, visit ADEQ's Ozone Action Days web page.

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Sulfur dioxide (SO₂)

Sulfur dioxide is the result of burning coal and oil. It is produced primarily by electric power plants, coal-burning factories, refineries, steel plants, and pulp and paper mills. It is a colorless, nonflammable, nonexplosive gas that reacts with other materials to form hazardous substances like sulfuric acid. Sulfur dioxides react with precipitation to form acid precipitation, better known as acid rain.

A continuous monitor measures sulfur dioxide. We report results in parts per billion (ppb) over a 24-hour period. Levels above 140 ppb exceed the NAAQS.

Health and other effects of elevated SO₂ levels

• Irritate upper respiratory tract and aggravate respiratory disorders, such as coughing, chest colds, asthma, and pneumonia.
• Increase incidences of emphysema, lung cancer, and chronic bronchitis.
• Damage plants; injure plant tissue; discolor leaves; stunt plant growth; reduce crop yields; and attack many trees.
• Physically deteriorate and discolor buildings; destroy paint pigments; corrode metals; and attach limestone, marble, and roofing slate.
• Erode statues.
• Attack fabrics; fade clothing, curtains, fabrics; ruin hosiery; and damage cotton, linen, nylon, and other synthetic fabrics.
• Weaken and disintegrate leather.
• Damage and destroy book bindings; yellow and disintegrate book pages.

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Particulates (PM-10 and PM-2.5)

Airborne particulates are a result of smoke, soot, and fly ash from factories or power plants. It includes minute pieces of solids or liquids dispersed into the atmosphere, primarily by combustion. The major particles from these industries are carbon, ash, oil, and grease. Particulate can also be produced by rock, sand and gravel processing and cement, steel, and iron industries. These industries discharge microscopic amounts of metals and metal oxides into the atmosphere. Total suspended particulate (TSP) results in visible air pollution: dust, smoke, haze, and mist.

Total suspended particulate (TSP) is measured by use of a PM-10 sampler. The sampler collects particles that are 10 micrometers (approximately 0.0004 inches) and smaller. We measure TSP in micrograms per cubic meter over a 24-hour period. Levels above 150 micrograms/cubic meter exceed NAAQS.

Fine particulate (PM-2.5) is measured by use of a PM-2.5 sampler. The sampler collects particles that are 2.5 micrometers (approximately 0.0001 inches) and smaller. We measure PM-2.5 in micrograms per cubic meter over a 24-hour period.

Health and other effects of elevated Particulate levels

• Aggravate respiratory disorders such as coughing, chest colds, asthma, and pneumonia.
• Increase incidences of emphysema, lung cancer, and chronic bronchitis.
• Obscure vision, leading to high accident potential.
• Corrode metals.
• Causes grime on buildings and belongings.
• Soil, disfigure, and damage stone, brick, paint, glass, and other composite materials.
• Damage plants and trees with dust deposits which solidify on plant surfaces and inhibit growth, injure plant tissue, and interfere with pollination.
• Alter weather and climate by increasing rainfall and reducing sunlight penetration.

* Formerly Air Pollution Standards Index (APSI)