Ozone Season: Are You at Risk?

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Like many areas around the country, hot sunny days in Southern Indiana are sometimes accompanied by ozone pollution. Ozone is formed by chemical reactions between other pollutants emitted from various sources such as factories and vehicles. Under certain weather conditions – clear skies, low humidity, warm temperatures and calm winds, levels can climb to concentrations that may be detrimental to health. Exposure to high levels of ozone can trigger asthma, worsen respiratory diseases, and reduce lung function.

During ozone season (April through September), ozone is monitored and air quality forecasts are provided to the public. A forecast team led by the Indiana Department of Environmental Management includes members from Evansville, Indianapolis, and Louisville. If conditions favor high ozone, an air quality action day or “Ozone Alert” is issued typically a day in advance so concerned citizens may avoid exposure and/or take voluntary steps to reduce pollution, such as conserving energy, using public transit, and postponing certain activities.

The U.S. Environmental Protection Agency (U.S. EPA) establishes air quality standards to protect the public health. A standard for ozone was first established in 1971 and has been strengthened over time as more was learned about its health effects. The current standard is set at an 8-hour average of 75 parts per billion (ppb).
The U.S. EPA’s Air Quality Index (AQI) is tied to the air quality standard and provides easy to follow guidance. When ozone is at moderate levels (code yellow), unusually sensitive people may feel the effects. At higher levels (code orange), air quality is unhealthy for sensitive groups such as children, teenagers, the elderly, and those with respiratory diseases. At these levels, individuals who are sensitive to ozone may still be active outside, but they should consider limiting exposure with more frequent breaks and less intensity. Code red levels are considered unhealthy for the general population. Fortunately, the Evansville area has not experienced those levels since 2005.

Ozone levels have been declining for over two decades, thanks to emissions reductions from power plants and other sources. In 2013, there were no ozone exceedances (code orange days) in the Evansville region. This is a significant improvement compared to 1988 when 67 code red days were recorded. While air quality has greatly improved, we may still need to issue Ozone Alerts so we urge everyone to know their AQI.

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4 COMMENTS

  3. The Ozone National Standard is WEAKER today than when the first USEPA National Ozone Standards were published in the 40 CFR (Code of Federal Register)back in the late 1970s.

    I’ll explain in detail what I mean and why this is true if you like in private email.

    I was going to post my brief in here but I think I’ll save it for later on.

    But rest assured that the Ozone levels are much higher these days and that the National Ozone Standards have been changed over the years to let more pollution exit in the air not less.

  4. The problem is that the method of monitoring ozone has been changed since the early 1970. The monitors read lower today than they did earlier.

    And they USEPA changed the way that they calibrate the ozone monitors to make it read less. See above.

    And the standards today allow a much higher dose or exposure concentration over a longer period of time before anything can be done to control the pollution in the air.

    Ozone is a indicator pollutant much like the canary in the coal mine is used to determine if the air is bad inside the mind. Ozone is measured but it’s not the only air pollutant in the air when ozone levels are measured in the high range. High ozone levels indicate the presence of other more dangerous photochemical oxidants in our air.

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