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Air Quality and Your Health

What is ozone?

Ozone is an odorless, colorless gas. Ozone occurs both in the Earth’s upper atmosphere and at ground level. Ozone can be good or bad depending on where it is found:

  • Good Ozone:  This is ozone that occurs naturally in the Earth’s upper atmosphere, 10-30 miles above the Earth’s surface. It forms a protective layer that shields us from the sun’s harmful ultraviolet rays.
  • Bad Ozone:  This is ozone that occurs in the Earth’s lower atmosphere, near ground level. This ozone is formed when pollutants from cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the sunlight. This is called ground level ozone. Peak ozone levels typically occur during hot, dry, stagnant summertime conditions. The ozone season in Tennessee occurs March 1 through October 31.

How might ground level ozone affect my health?

Ozone can irritate the respiratory system.  When this happens, you might start coughing, feel a throat irritation, and/or experience an uncomfortable sensation in your chest.

Ozone can reduce lung function.  Ozone can make it more difficult for you to breathe as deeply and vigorously as you normally would. If you are exercising or working outdoors, your breathing may be more shallow and rapid.

Ozone can aggravate asthma.  When ozone levels are high, more asthmatics have asthma attacks that require going to a doctor or using more medicine.

Ozone can inflame and damage the lining of the lungs. This could cause permanent damage that might have long-term health effects and a lower quality of life.

Ozone is suspected to have other effects on health.  Ozone may aggravate chronic lung disease such as emphysema and bronchitis.  It may also reduce the body’s ability to fight infection.

Who is most at risk from ozone?

  • Children. Children often spend more time outdoors playing. Children also are more likely to have asthma which can be aggravated by the ground level ozone.
  • Adults who are active outdoors. These people have a higher exposure to ozone because physical activity (jogging or outdoor work) causes them to breath faster and more deeply. Ozone can get into the deeper parts of the lungs that can get damaged more easily.
  • People with respiratory diseases. There is no evidence that ozone causes asthma, but it does make the lungs more sensitive to the effects of ozone.
  • People who are just more sensitive to ozone. Scientists don’t know why, but some healthy people are simply more sensitive to ozone than other people. These people may experience more health effects from ozone exposure than the average person.

What can I do to protect myself and my family?

The best way to protect your health is to find out when ozone levels are elevated and take simple precautions to minimize exposure. Follow the air quality index to know what actions to take.

What can I do to reduce ozone levels?

  • Conserve energy--at home, at work, everywhere!
  • Drive less. Try walking, biking or using public transportation.
  • Carpool
  • Make sure your car, boat, and other engines are well- tuned.
  • Take care not to spill gasoline when you fill the tank of you car or lawn and recreational equipment.  Be sure to tighten your gas cap securely.
  • Keep your tires properly inflated.
  • Tightly seal the lids of chemical products such as household cleaners and garden chemicals. This will limit evaporation.
  • Use environmentally safe paints and cleaning products whenever possible.
  • Maintain your lawn according to the recommendations below during the ozone season. 

How do I maintain my lawn to reduce ozone? 

The small engines found in gasoline-powered lawnmowers, leaf blowers, string trimmers and other yard care equipment release as much as 25 percent raw, unburned gasoline.  An hour of lawnmower operation produces as many emissions as a 1997 mid-sized car driven 125 miles.  Follow these recommendations to help reduce ozone:

Water lawns moderately but not excessively.  Lawns respond with ample growth when over-irrigated. In addition to more mowing and therefore more air pollution, excessive watering creates thatch buildup and other landscape problems. Wait to water until you see "footprinting" in the lawn. Footprinting refers to grass that takes a long time to spring upright after walking through the lawn. Reset sprinkler clocks from season to season to save water and preserve air quality. Watering for the entire growing season based on clocks set for peak, summer hot-spells creates excessive mowing during other periods.

Fertilize lawns in the fall.  Late season fertilization in fall, rather then spring, eliminates excessive spring lawn growth and minimizes the need for mowing. It delivers all the benefits of spring fertilization including early green-up, good color and thickness without creating excessive spring mowing chores. Less mowing means less air pollution. Fall fertilization generally lasts through early summer.

Use slow release fertilizer products in spring and summer.  In late spring and summer, use slow-release fertilizer products. This minimizes mowing by eliminating the excessive top growth seen with fast acting fertilizers. Lawn thickness and quality can be maintained to minimize weed invasion while also minimizing mowing chores and air pollution.

Delay lawn mowing by 24 or perhaps 48 hours during summer advisories.  People are still urged to keep in mind the "one-third mowing rule." That is, never remove more than 1/3 of the grass blade in a single mowing. For example, 3 inches is an average recommended height to maintain lawn grass today. Mowing to return a lawn to 3 inch height is no problem when the lawn grows to 4 or 4.5 inches. If a lawn reaches 5 inches, mowing to a 3 inch height stresses the turf. This is in addition to the concern over what to do with the long clippings. In general, lawns grow slower in summer due to the heat. Kentucky bluegrass is a cool season plant and tends to languish in hot weather. It should be possible in most cases to delay mowing with no concerns for lawn health. Plan mowing based on consideration of smog advisories plus the one-third rule, not a calendar schedule.

Mow in the evening or cooler part of the day when it is cloudy and there are breezes.  This minimizes ozone formation by moving mowing to a time of day when temperatures are less favorable for ozone formation.

Reduce lawn areas when renovating landscapes.  Less lawn means less mowing. Minimizing turf areas may be part of a plan to renovate an overgrown landscape and save on water costs. An example of minimizing turf are is to add a deck or other outdoor living area.

Explore other options.  Other mowing options such as hand-pushed reel mowers, or electric mowers are excellent alternatives that are not a concern during smog advisories. Sweeping with a broom is a manual alternative to leaf blowers, as are hand shears instead of gasoline powered trimmers. Note that EPA and CARB-certified mowers manufactured after 1999 are cleaner burning and cut down on emissions.

Additional tips to minimize pollution include: avoid spilling fuel during filling operations, fill tanks only 3/4 full to allow for expansion, tightly screw on the gas caps of the mower and fuel can, place gas containers in a cool place out of the sun, and reduce mower operating time to that essential to cutting the lawn.

Maintaining mower engines is key to burning fuel as cleanly as possible. Change oil after 25 hours of use and use 30W oil instead of a multi-weight type in warm weather. Clean or replace the air filter regularly, at least every 3 months or when the oil is changed. Clean, re-gap or replace spark plugs. Keep the engine and underside of the mower deck clean of grass buildup. Sharpen the mower blade regularly for cleaner cuts that reduce pollution by requiring less fuel.

Where can I go for more information on ozone?

For more information on ozone, visit the Tennessee Department of Environment and Conservation's  website or the Environmental Protection Agency's website.