What is Ozone?

Ozone is an odorless, colorless gas which occurs naturally in the earth’s upper atmosphere, where it shields us from the sun’s harmful rays (‘good ozone"). At ground-level, ozone is a noxious pollutant created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of sunlight ("bad ozone").

The Good and the Bad

Whether ozone is good or bad depends on its location. Ozone occurs in two layers of the atmosphere. The stratospheric or "good ozone" layer extends from about ten miles above the earth’s surface upward to about 30 miles above the earth’s surface and protects life on earth from the sun’s UV-b rays. The layer surrounding the earth’s surface is the troposphere. The troposphere extends to a level about ten miles up, where it meets the stratosphere. Here, ground-level or "bad ozone" is an air pollutant that damages human health, vegetation, and many common materials. It is a key ingredient in urban smog.

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Good Up High

Ozone occurs naturally in the upper atmosphere or stratosphere when 3 atoms of oxygen are combined. Up high, ozone is produced and destroyed at a constant rate. The ozone layer is produced when solar radiation splits oxygen molecules, which then combine with other oxygen molecules to form ozone. However this "good ozone" layer is gradually being destroyed by manmade chemicals, called ozone depleting substances. These damaging substances, such as chloroflurocarbons (CFCs) and halons, are found in coolants, foaming agents, solvents, aerosol propellants, and in many consumer products.

Ozone depleting substances degrade slowly and can remain intact for many years as they move up through the earth’s atmosphere to the stratosphere. It can take years for ozone depleting substances to reach the stratosphere, so even after substances are eliminated, their impact on the ozone layer will continue well into the future. Once the ozone depleting substances reach the stratosphere, they are broken down by the intensity of the sun’s ultraviolet rays and release chlorine and bromine molecules, which destroy "good ozone." One chlorine or bromine molecule can destroy 100,000 ozone molecules, causing ozone to disappear faster than nature can replace it. In fact, people are generally familiar with the term "a hole in the ozone layer," which refers to an area where ozone has been most significantly depleted over sections of the north and south polar regions (ozone depletion accelerates in extremely cold weather conditions).

The Threat of Depleting Good Ozone

As the stratospheric ozone layer is depleted, higher UV-b levels reach the earth’s surface. Increased UV-b can lead to more cases of skin cancer, cataracts, and impaired immune systems. Many of our essential crops, such as corn, barley, hops, wheat and soybeans, may become damaged, decreasing their yield. Phytoplankton, a plant in the ocean, also is affected. Depletion of this important link in the marine food chain could reduce the number of fish in the ocean. It also can increase the level of carbon dioxide in the atmosphere because phytoplankton absorbs carbon dioxide in their food and energy making processes.

What is Being Done About the Depletion of Good Ozone?

In the United States, the U.S. Environmental Protection Agency continues to establish regulations to phase out ozone depleting substances. The Clean Air Act requires warning labels on all products containing CFCs or similar substances, prohibits the release of refrigerants used in car and home air conditioning units and appliances into the air.

Montgomery County has joined Cities for Climate Protection, a worldwide effort coordinated by the International Council for Local Environmental Initiatives (ICLEI). The county joins over 350 cities and counties working towards the reduction of local greenhouse gas emissions. Learn more about DEP's Climate Protection Initiatives.

• Make sure that technicians working on your car air conditioner, home air conditioner, or refrigerator are certified by an EPA approved program to recover the refrigerant.  More...
• Have your car and home air conditioner and refrigerator checked for leaks.
• Substitute "pump sprays" for aerosol can products. More...
• Purchase home products that display the EPA Energy Star label.
• Plant deciduous trees in strategic locations around your home. Trees store carbon during photosynthesis and can remove 50 pounds of carbon in a year. Select landscaping to conserve energy.  See Shady Ideas for Home Landscaping.
• Use a mulching lawnmower and grasscycle your lawn clippings.  Compost leaves and other yard trimmings.  Managing leaves and clippings on site reduces pollution from transporting and handling materials at distant compost facilities or incinerators.
• Use a pushmower instead of a power mower. This will reduce carbon dioxide emissions by 80 pounds per year.
  

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"Bad Ozone"

When ozone is located in the troposphere, the lowest ten miles of the atmosphere, it is called "ground-level" ozone and is considered "bad ozone." Ground-level ozone is created when intense sunlight reacts with nitrogen oxides (NOx) and volatile organic compounds (VOCs). High concentrations of ground-level ozone occur during hot, sunny days, when the flow of air is limited or stagnant and a mixture of VOCs and NOx is present. The main ozone-causing pollutants, VOCs and NOx, come from many sources such as the fumes from vehicles, lawnmowers, and boats, or emissions from power plants and industrial facilities. This is one pollution problem driven by individuals as much as industry. Automobiles account for 30 to 40 percent of pollutants that cause ozone in our area. Another source of ozone in Montgomery County comes from the migration of NOx from other areas. Winds can carry NOx emissions hundreds of miles away from their original source.

Health Effects of Ground-Level Ozone

When ozone forms at ground-level it can be harmful to our health. Ozone can inflame and damage the lining of the lungs in a manner scientists suggest is similar to the effect of sunburn on the skin. Ozone damages cells which line the air spaces in the lung. Within a few days, the damaged cells are replaced and the old cells are shed, much as skin peels after sunburn. Repeated damage may change the lung tissue permanently.

Ozone can also:

• aggravate bronchitis, heart disease, emphysema and asthma;
• lead to hospital admissions and emergency room visits (10-20% of all summertime respiratory-related hospital visits in the northeastern U.S. are associated with ozone pollution);
• impair the body’s immune system defenses, making people more susceptible to respiratory illnesses, including bronchitis and pneumonia.

Children, people who work outdoors or exercise outdoors regularly, the elderly, and individuals with pre-existing respiratory problems are most at risk.

People who work or exercise outside:

Physical activity (such as jogging or outdoor work) causes people to breathe faster and more deeply. During activity, ozone penetrates deeper into parts of the lungs that are more vulnerable to injury.

Children:

Children breathe more rapidly and inhale more air pollution per pound of body weight then adults. Because children’s respiratory systems are still developing, they are more susceptible than adults to environmental threats. Children often spend a large part of their summer vacation outdoors, engaged in vigorous activities either in their neighborhood or at summer camp. Children are also more likely to have asthma or other respiratory illnesses.

Asthmatics and people with other respiratory diseases:

There is no evidence that ozone causes asthma or other chronic respiratory disease, but these diseases do make the lungs more vulnerable to the effects of ozone. Thus individuals with these conditions will generally experience the effects of ozone earlier and at lower levels than less sensitive individuals.

Even healthy adults:

Even healthy adults can experience health problems on high ozone days, especially while exercising or working outdoors. When high concentrations of ground-level ozone are present, inhaling it may trigger a variety of health problems including chest pain, coughing, nausea, throat irritation, and congestion. Even moderately exercising healthy adults can experience reductions of 15 to more than 20 percent in lung function from exposure to low levels of ozone over several hours.

Crops:

Ground-level ozone damages plant life and is responsible for 500 million dollars in reduced crop production in the United States each year. It interferes with the ability of plants to produce and store food, making them more susceptible to disease, insects, other pollutants, and harsh weather.

Ozone and Montgomery County

Ozone is a serious issue in our region. Montgomery County is part of the Washington Metropolitan "serious" non-attainment area for the EPA’s one-hour ozone standard. Currently, the National Ambient Air Quality Standard for ozone is a one-hour standard of 120 ppb. The one-hour standard was revised in July 1997 when the EPA issued a new eight-hour average standard of 80 ppb. A 1999 court ruling has blocked promulgation of the 8-hour standard. During recent summers, there have been an average of approximately 5 days during which the region experienced Code Red conditions (levels in excess of the 1-hour federal health standard for ground-level ozone.) Typically during these summers the region has also experienced an average of 29 Code Orange condition days (violations of the eight-hour 80 ppb standard).

An episode of high ozone usually occurs during afternoons and early evenings and may or may not extend over the entire region. However, Montgomery County often experiences high ozone levels sometimes during days when the region is Code Orange or Code Red.

Ground Level Ozone History for the Baltimore-Washington MetroArea Reflects the number of days the region exceeded the U.S. EPA National Air Quality Standard (0.12 parts-per-million, as a one-hour average concentration not to be exceeded more than once a year). Remember that ground-level ozone production is influenced by  temperature and sunlight as well as VOCs and NOx.

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Government Actions

Montgomery County has developed initiatives to reduce ozone precursor emissions on Code Red days. The County offers a "Code Red Ride Free" program on its Ride-On buses to encourage residents to park their vehicles. The County refuels its fleet after 7:00 p.m., and establishes reductions in lawn mowing, spraying of herbicides, paint stripping, and road paving. The County also places additional restrictions on open burning and, if the power-grid is capable, the Resource Recovery Facility curtails its burning operations to 70 percent.

The County's new Vehicle Maintenance and Repair Manual, now offers a ready-made package of current, cost-effective pollution prevention measures.

The Federal Government has been working to improve air quality through programs regulating cleaner fuel formulations and automobile efficiency and emission standards. State programs include vehicle emission inspections and, a June-August ban on open burning in many counties, including Montgomery -- which has its own regulations on open burning.

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Do Your Share for Cleaner Air

During the summer months, our thoughts turn to all the fun of summer: family vacations, romantic picnics, and barbecues with friends. However, despite our appreciation for warmer weather and bright sun, the holiday weekend also heralds the arrival of the area's ozone and smog season.

While most of us realize that atmospheric pollutants are harmful to our health and the environment year-round, this is especially true when temperatures are in the upper 80's and 90's, when natural and man-made sources of nitrogen oxides (NOx) and Volatile Organic Compounds (VOCs) undergo a chemical reaction in sunlight to create ground-level ozone or smog.

Code Red -- Ozone Action Days

Become more aware of air quality notices. Newspaper, radio, and television weather reports will continue to provide the familiar color-coded forecasts of air quality. Pay special attention to Code Orange and Red days: air quality approaches unhealthful, or is unhealthful.

What Can You Do?

There are constructive steps that you can take well beyond avoiding unhealthful exposure to ozone. And although the greatest risk is during the hottest months from mid-June to mid-August, the season to take action is upon us. Changing behavior now can add up to important air quality savings later on this summer -- and beyond.

Code Red Musts

• Brown bag your lunch to avoid mid-day use of your car.
• Take transit, carpool, bike, telecommute, or walk to work.
• Combine errands and limit driving.
• Avoid idling your car. (If you expect to idle for more than 30 seconds, you will save gas and reduce pollution by turning the engine off and restarting). Park your car and go into restaurants and banks etc.
• Do not mow your lawn or use other gas-powered outdoor equipment.
• Do not refuel your vehicle until after dark.
• Substitute low-VOC latex or water-based paints for oil-based paints, or avoid painting altogether.
• Replace aerosol and other household products that contain solvents, with non-solvent based products.
• When air quality is in the unhealthy range, at-risk individuals should reduce outdoor activity.

Did You Know?

• A typical lawnmower run for one hour emits pollution equal to one car driven for 635 miles.
• Air pollution costs the nation approximately 50 billion dollars in health care costs each year.
• Approximately 25 percent of all the nitrogen compounds that enter the Chesapeake Bay are deposited from the air.

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More Information

• Air Quality Forecasts: 240.777.7777
• Montgomery County Commuter Services : 301-565-5870
• Rideshare/Commuter Connections: 800.745.RIDE
• Code Red - Ride Free: 240.777.7433
• Ozone Action Days Program: 800.745.7433

Maryland

• Maryland Department of the Environment
• Maryland Air Quality Forecast Page
• Maryland Ozone Information Page

Regional Ozone Information & Real Time Data

• North Central Texas COG
• Maine DEP

US EPA

• Office of Air and Radiation
• Office of Air Quality Planning and Standards
• Office of Mobile Sources

Miscellaneous

• Ozone Transport Assessment Group: Air Quality Analysis Page
• STAPPA/ALAPCO
• Environmental Council of the States
• The Weather Channel