What an 'Ozone Action Day' really means

Ozone Action Day

SAN ANTONIO - Ozone action days are fairly common as we move through May and especially in the heat of our South Texas summers. But do they really mean and why can it be such a danger to our health? To understand that first let's talk about what Ozone is.

There's actually two types of ozone that we hear about today, one good and one bad:

Good Ozone. Ozone occurs naturally in the Earth's upper atmosphere 6 to 30 miles above the Earth's surface where it forms a protective layer that shields us from the sun's harmful ultraviolet rays. Man made chemicals are known to destroy this beneficial ozone. An area where the protective "ozone layer" has been significantly depleted-for example, over the North or South pole-is sometimes called "the ozone hole.”

Bad Ozone. In the Earth's lower atmosphere, near ground level, ozone is formed when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight. Ozone at ground level is a harmful air pollutant. Maybe you've heard of this called by another more common name "smog".

Ground-level ozone is a colorless and highly irritating gas that forms just above the earth's surface. It is called a "secondary" pollutant because it is produced when two primary pollutants react in sunlight and stagnant air. These two primary pollutants are nitrogen oxides (NOx) and volatile organic compounds. (VOCs)

High concentrations of ozone near ground level can be harmful to people, animals, crops, and other materials. Ozone can irritate your respiratory system, causing you to start coughing, feel an irritation in your throat and/or experience an uncomfortable sensation in your chest. Ozone can also aggravate those with chronic asthma and emphysema. it also affects sensitive vegetation and ecosystems, including forests, parks, wildlife refuges and wilderness areas. In particular, ozone harms sensitive vegetation during the growing season.

So for this reason the Texas Commission on Environmental Quality issues "Ozone Action Days" when the air quality is forecast to reach predetermined harmful levels. The good news is there are some simple things we can all do to help cut down on the "bad" ozone.

Choose a cleaner commute — car pool, use public transportation, bike or walk when possible.

Combine errands to reduce "cold starts" of your car and avoid extended idling.

Be sure your tires are properly inflated.

Keep car, boat and other engines properly tuned, and avoid engines that smoke.

Follow gasoline refueling instructions for efficient vapor recovery. Be careful not to spill fuel and always tighten your gas cap securely.

Use environmentally safe paints and cleaning products whenever possible.

Some products that you use at your home or office are made with smog-forming chemicals that can evaporate into the air when you use them. Follow manufacturers' recommendations for use and properly seal cleaners, paints, and other chemicals to prevent evaporation into the air.

Conserve electricity. Consider setting your thermostat a little higher in the summer and lower in winter. Participate in local energy conservation programs.

Consider using gas logs instead of wood. If you use a wood-burning stove or fireplace insert, make sure it meets EPA design specifications. Burn only dry, seasoned wood.

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