Air quality in Columbus

What is the air quality in Columbus Ohio?

Columbus air quality is generally clean. In 2019, Columbus air quality index (AQI) averaged an annual score of 37 or “good.” The US Environmental Protection Agency (EPA) describes “good” air quality as air that generally poses little to no health risk. Similar “good” ratings have been achieved each year in Columbus since 2012.

While such optimistic annual ratings show general success in keeping air pollution levels low, it only takes several hours of elevated air pollution levels to cause adverse health effects in the general public.

From 2016 to 2018, Franklin County, of which Columbus is the county seat, experienced a weighted average of 4.3 unhealthy ozone days annually, exceeding the federal target allowing no more than 3.2 unhealthy days a year.¹ Columbus air quality has in fact never met this ozone target.

While the number of unhealthy ozone days have been on the decline in recent years, “moderate” ozone levels, which exceed federal “good” standards but are not classified as “unhealthy,” increased from 18 percent in 2018 to 21 percent in 2019. This recent gain in ozone concentrations may, however, be more indicative of weather than emissions. As climate change drives temperatures higher, ozone formation becomes accelerated. From July to October, Columbus experienced hotter temperatures in 2019 than the average of temperatures in the last decade from 2007 to 2016.²

July was the hottest month of the year in 2019 (2.9°F higher than the month average from 2007 to 2016), with below-average precipitation. Correlating to the increased temperatures, 4 of the 5 highest ozone days also occurred this month, with the fifth occurring on June 28.

National ozone standards became more stringent in 2015, when the U.S. EPA lowered allowable levels from to 75 ppb to 70 ppb.³ The new standard better serves children, the elderly, and people with heart and lung conditions, who are all categorized as “sensitive” to air pollution. In order to meet these more stringent targets and better serve sensitive groups, Columbus will need to implement additional emission standards to drive down the presence of ozone precursor pollutants, nitrogen dioxide (NO₂) and volatile organic compounds (VOCs), to combat the effects of a warming climate.

Follow Columbus air quality data at the top of this page or on the IQAir AirVisual app for the most current health data and advisories.

Why does Columbus have unhealthy air quality?

Columbus unhealthy air quality is largely attributable to two pollutants: fine particulate matter (PM2.5) and ozone.

According to the Central Ohio Air Report, a majority of days in Central Ohio from November 2018 to October 2019 experienced “good’ US Air Quality Index (AQI) levels. In the summer, where ozone levels tend to be most severe, 22 percent of days that exceed US “good” AQI standards were a result of high ozone. 11 percent of all days that exceeded this same standard, meanwhile, were the result of high levels for fine particle pollution, PM2.5.

Columbus’s worst air pollution rating comes from ozone pollution. Columbus ozone received an “F” rating from the 2019 “State of the Air” report. The ozone pollution season coincides with summer, running from March through October. Hot, sunny conditions are required for ozone formation, which is created when precursor pollutants, nitrogen oxides (NO₂) and volatile organic compounds (VOCs), cook in sunlight.

Primary ozone sources include vehicle emissions from cars, trucks, and buses as well as power plants and other sources of combustion. Columbus’s worst unhealthy ozone days, where ozone exceeded AQI levels of 100, tend to correspond with wind blowing in from the southwest or west. These trends tend to correspond with maximum readings at monitors to the northeast of the city, such as the New Albany air quality monitoring site and London air quality monitoring site.

While Columbus air quality meets annual PM2.5 targets, the city received a “B” rating for having one day in the “orange” US AQI category. Five months in 2019 exceeded the US AQI “good” rating, February, March, July, November, and December.

Does Columbus have cleaner air than Cincinnati?

Despite Columbus’s larger population and higher traffic burden, air pollution levels here tend to be similar to those of Cincinnati.

For ozone pollution, both Hamilton County (including Cincinnati) and Franklin County (including Columbus) were rated an “F” in 2019 for exceeding the federal allowance of unhealthy ozone days. Hamilton County, with Cincinnati, had nearly twice as many unhealthy ozone days (8.5 unhealthy days), however, as Franklin County (4.3 unhealthy).

For PM2.5, Columbus fared worse than Cincinnati, with an annual PM2.5 level of 11.6 μg/m³, compared to Columbus, with an annual PM2.5 level of 11.2 μg/m³. While both cities met US EPA PM2.5 targets for annual PM2.5 (12 μg/m³), both Columbus and Cincinnati failed to meet the more stringent World Health Organization (WHO) target of 10 μg/m³.

Is Columbus air quality improving?

Columbus pollution has improved steadily and significantly over the last several decades.

Since 2000, the number of unhealthy ozone days has dropped from an average of 39.3 days to 4.3 days in 2018. Despite this improvement in “unhealthy” ozone days, the number of “good”-rated ozone days dropped from 81% to 78% in 2019 compared to the year prior. This trend is likely attributable to above average temperatures and little precipitation, as compared to 2018.

Average annual PM2.5 levels, meanwhile, have fallen from an average of 17.1 μg/m³ to 11.6 μg/m³ from 2000 to 2019. As with ozone levels, however, 2019 was an off-trend year, showing a 73 percent increase from 2018’s annual PM2.5 concentration of 6.7 μg/m³.

What does the Columbus smog alert mean?

Columbus smog alerts are advisories indicating that air pollution has or will, at minimum, reach unhealthy levels for sensitive individuals. Franklin county, which includes Columbus, has up to 719,429 sensitive individuals that would be affected by a level one “orange” smog alert.

The US Environmental Protection Agency (EPA) and numerous local agencies monitor air pollution regulated under the Clean Air Act. These pollutants include PM2.5, PM10, ozone (O₃), carbon monoxide (CO), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂). The EPA uses an Air Quality Index (AQI) to weigh pollutants into a single, easy-to-understand number so that a comparable health risk can be assessed across all six pollutants.

Smog alerts in Columbus are issued by the Mid-Ohio Regional Planning Commission (MORPC) when any given pollutant registers, or will likely register, an AQI reading over 100.⁴ Out of the six monitored pollutants, ozone and particulate matter are the most prevalent pollutants at risk to human health and are therefore most often the cause of air quality alerts.

Current AQI values and individual pollutant readings are shared in real-time at the top of this Columbus air quality page. During smog alerts, the general public and sensitive individuals should avoid strenuous physical activity, especially during the hottest part of the day.

+ Article Resources

[1] State of the Air – 2019. (2019).
[2] Mid-Ohio Regional Planning Commission (MORPC). (2019). Central Ohio air quality end of season report.
[3] Burger B. (2018, August 5). Air quality still poor in Columbus; EPA gives metro area 3 years to meet standards.
[4] The Columbus Dispatch. (2020, August 9). Air quality alert issued for Columbus area.