What Am I Breathing Today?

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Hotline, Spring 2003

by Suzanne Seppi, GASP Executive Director

Warm weather is just around the corner in Pittsburgh, and we are even getting a taste of it as this issue goes to press. While we enjoy the outdoors, looking for greenery to brighten the drab winter ground, we might also be taking in a vista or two. Here is where we note that the air around us, too often, is hazy. Haze in the eastern United States is formed of very fine particulates created predominantly from combustion sources, such as coal-fired power plants and diesel exhaust, and there are serious health implications from this sort of air pollution. When the really hot weather arrives, ozone season begins, and we start hearing about ozone action days. We may know that ground-level ozone is not good, but sometimes we just don’t really know whether the air quality is okay for children to be very active outdoors or for a person with a heart condition to take a walk. Understanding the risks from high pollution days is most important to special populations such as the young, elderly, and those with respiratory or heart disease.

For example, more than 50,000 hospital admissions per year for chronic obstructive pulmonary disease (COPD) and other respiratory diseases are attributed to ground-level ozone exposure in the eastern United States.1 Toxicology studies indicate that air pollution increases blood pressure and constricts blood vessels, and may even increase build up of cholesterol in the blood vessels.2 Fine particulate pollution is associated with premature death.

For air quality guidance on a daily basis, we can reference the EPA Air Quality Index (AQI) as an air quality indicator for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect against harmful health effects.

How does the AQI work?

The AQI can be compared to a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health danger.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. So, AQI values below 100 are generally thought of as satisfactory in the AQI. When AQI values are above 100, air quality is considered to be unhealthy — at first for certain sensitive groups of people, then for everyone as AQI values get higher.

The purpose of the AQI is to help you understand what local air quality means to your health.

Following are the six levels of health concern and what they mean according to the Air Quality Index:

Good: The AQI value for your community is between 0 and 50. Air quality is considered satisfactory and air pollution poses little or no risk.

Moderate: The AQI for your community is between 51 and 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of individuals. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.

Unhealthy for Sensitive Groups: Some groups are more vulnerable to air pollution than others. For example, children and adults who are active outdoors and people with respiratory disease are at greater risk from exposure to ozone, while people with heart disease are at greater risk from carbon monoxide and fine particulates. Some people may be sensitive to more than one pollutant. When AQI values are between 101 and 150, members of sensitive groups may experience health effects. The general public is not likely to be affected when the AQI is in this range according to EPA.

Unhealthy: AQI values are between 151 and 200. Everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects.

Very Unhealthy: AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects.

Hazardous: AQI values over 300 trigger health warnings of emergency conditions. The entire population is more likely to be affected.3

How is a community’s AQI calculated?

Air quality is measured each day by networks of monitors in the area. These raw measurements are then converted into AQI values using standard formulas developed by the EPA. An AQI value is calculated for each of the individual pollutants in an area (ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide). The highest of the AQI values for the individual pollutants becomes the AQI value for that day. For example, if on July 12 a certain area had AQI values of 90 for ozone and 88 for sulfur dioxide, the AQI value would be reported as 90 for ozone on that day.

  • You can learn what the AQI is each day in areas of Allegheny County by calling 412-578-8179.
  • Allegheny County groups its monitoring system into 9 separate geographic groups to give a more local AQI, but each group may not contain monitors for all pollutants, according to Jayme Graham of the Allegheny County Air Quality Division. The highest index for each pollutant at each site will be the AQI pollutant mentioned for that site.
  • In Allegheny County, as ozone monitors may not be present in some geographic AQI sites, it will be important to pay attention to ozone action day announcements since ozone is a regional pollutant.
  • The data for the AQI is recently monitored data based on time periods required by standards for measuring each pollutant.
  • You may also find the AQI reported in the newspapers or hear it on radio and television news broadcasts in some regions.
  • If you would like to report an air pollution complaint: Call the Allegheny County Health Department at (412) 687-2243. Remember that the more people that report a complaint, the more likely that an inspector will be sent promptly to investigate the complaint.

    1. Abt Associates. Adverse Health Effects Associated with Ozone in the Eastern United States, October 1999.
    2. For toxicological research see, e.g., Suwa, T., Hogg, J.C., et al., Particulate Air Pollution Induces Progression of Athlerosclerosis. J. Am Coll. Cardiol. Vol. 39, pp 943-945, March 20, 2002; Ibald-Mulli, Al, Stiber, J., et. al., Effects of Air Pollution on Blood Pressure: A Population-Based Approach. Am. J. Public health, Vol. 91, pp571-577, 2001.
    3. Table and information for levels of concern from EPA: http://www.epa.gov/airnow/aqibroch/aqi.html