What's an air quality alert? Which Tennessee city has worst air quality and what to know ahead of summer
As summer and the end of school approach, many families are gearing up to spend the hot days outside, but that may do more harm than good depending on the day.
The United States Environmental Protection Agency monitors the air quality for days when it may be hazardous to health. In most parts of Tennessee, there are not many days where it is truly unsafe to go outside, so warm weather is still enjoyable. The closer you are to a metropolitan area, the more likely it is that you will have times when it is unsafe to go outside.
Here are some things to know about air quality alerts and what they mean for Tennessee.
What is an air quality alert?
Air quality is measured on the Air Quality Index, or AQI. The index was created by the Environmental Protection Agency in 1999. Air quality alerts, or AQAs, are issued when the AQI reaches above 50. Above 50, certain groups are more vulnerable to the air than others.
Here is the scale for the AQI:
Green is 0 to 50: Air quality is satisfactory and poses little to no risk.
Yellow is 51 to 100: Air quality is acceptable but may be a risk for some people particularly those sensitive to air pollution.
Orange is 101 to 150: Members of sensitive groups may experience health effects, but the general public is less likely to be affected.
Red is 151 to 200: Some members of the general public may experience health effects.
Purple is 201 to 300: The risk of health effects is increased for everyone.
Maroon is 301 to 500: These are emergency conditions where everyone is more likely to be affected.
When yellow or higher, the groups referred to as being at risk include the elderly, children and those with heart or lung conditions.
What causes bad air quality?
There are a number of factors that affect the air quality, however, it has been linked to a few key elements which have caused the alerts to be more frequent in recent years. Outdoor and indoor air pollution, airborne allergens, disastrous weather, and warmer temperatures are all things that affect the air quality.
Wildfire smoke, such as the smoke from Canadian wildfires that have flared up in British Columbia and Alberta, can also contribute to poor air quality, prompting current warnings in Milwaukee and other parts of the country.
To measure air quality, there are four major pollutants monitored and regulated by the Clean Air Act: ground level ozone, particulate matter, carbon monoxide and sulfur dioxide.
Ground level ozone, a major component of smog, can cause coughing, chest tightness or pain, decrease lung function and worsen asthma and other chronic lung diseases. Carbon monoxide decreases the amount of oxygen reaching the body’s organs and can cause flu-like symptoms and chest pain in those with cardiovascular disease. Normally sulfur dioxide is kept out of the body by the nasal passages, but when physical exertion necessitates mouth breathing, the irritating gas can cause wheezing, shortness of breath and tightness in the chest.
Particulate matter, or PM, contains microscopic liquid droplets or solids that are so small they can be inhaled and cause health problems. Some particles less than 10 micrometers in diameters can get into your lungs and bloodstream. This is four times the size of the particulate matter measured by the EPA to determine particulate pollution annually.
What to do when an air quality alert is issued?
When an air quality alert is issued, it is best to keep people who are at risk inside as much as possible. Even if you are not someone at risk for the lower levels of caution on the AQI, it is best to limit yourself to outdoor exposure as well.
It is also important to not burn debris or anything else when AQAs are issued as the smoke would contribute more the quality of air decreasing.
Does Tennessee have good air quality?
According to the American Lung Association, Tennessee has relatively clean air. Only 15 counties report the ozone levels for each day, and 16 report the particle pollution for each day. For 2023, 8 of the 15 measured cities had zero days where health would be in danger from poor air quality.
High ozone days are measured by the number of days when the air quality reached over 100, or into the orange category. The days are added up on a weighted scale where the higher the AQI category, the bigger the number. That number is then divided by three to get a score. It uses an A, B, C scale where A is zero and F is anything three or higher.
Shelby County had the worst grade with an F as there were 12 days where the quality reached orange and 2 days where it reached red. The next highest county was Davidson County where there were only three days in the orange category. It had a C grade.
Particle pollution is a bit more complicated in the way it's measured. The scores are based on the national standard for particulate matter smaller than 2.5 micrometers. If areas had more concentration of the particulate matter, they would have higher scores. Counties with values greater than 9 will receive a "Fail."
In Tennessee, only two counties of the 16 measured failed the particle pollution scale: Davidson and Knox County. Davidson County had a score of 9.1, and Knox County had a score of 9.4.
What cities have the worst air quality?
According to the American Lung Association, the worst place for ozone pollution in the United States is the Los Angeles-Long Beach area in California. The score for number of days with high ozone levels was 175.2. For particulate pollution, the worst city in the United States is Bakersfield, California with a score of 18.8.
Cities with high ozone levels annually
Los Angeles-Long Beach, California: 175.2
Visalia, California: 103
Bakersfield, California: 87.5
Fresno-Madera-Hanford, California: 52.2
Phoenix-Mesa, Arizona: 47.7
Denver-Aurora, Colorado: 40.3
Sacramento-Roseville, California: 29.3
San Diego-Chula Vista-Carlsbad, California: 25.2
Salt Lake City-Provo-Orem, Utah: 24
Houston-The Woodlands, Texas: 23.2
Cities with high particulate pollution annually
Bakersfield, California: 18.8
Visalia, California: 18.4
Fresno-Madera-Hanford, California: 17.5
Eugene-Springfield, Oregon: 14.7
San Jose-San Francisco-Oakland, California: 14.3
Los Angeles-Long Beach, California: 14
Sacramento-Roseville, California: 13.8
Medford-Grants Pass, Oregon: 13.5
Phoenix-Mesa, Arizona: 12.4
Fairbanks, Alaska: 12.2
Why are air quality alerts more frequent?
Air quality alerts are issued during times when ground level ozone and/or fine particle concentrations reach unhealthy levels in an area. As the climate on Earth gets hotter, air quality alerts can be expected to occur more often as warmer temperatures cause more damage via wildfires, smog spread and severe weather.
This article originally appeared on Memphis Commercial Appeal: Air Quality Index: What's unhealthy? What to know in Tennessee
