Air quality in Oklahoma City

Is Oklahoma City polluted?

Oklahoma City (sometimes abbreviated to OKC) experiences periods of high air pollution, and recent measures indicate that the city’s air quality may be worsening.

Oklahoma City air quality is typically defined by a combination of PM2.5 and ozone. These two pollutants, of the 6 closely monitored and controlled by the U.S. Environmental Protection Agency (EPA), are most often responsible for causing the city’s air quality measurements to reach dangerous levels. For this reason, the Air Quality Index (AQI) formula weighs them more heavily, resulting in these measures frequently dictating the final AQI measurement.

PM2.5 pollution in OKC

PM2.5 describes a combination of suspended particulate matter (PM) smaller than 2.5 micrometers in diameter. A PM2.5 sample may include:

• wind-blown dust and dirt from nearby agricultural fields
• soot (or black carbon) from chimneys
• chemicals and smoke from vehicle exhaust
• pathogens like bacteria and viruses from people, plants, and animals

The near-microscopic size of PM2.5 allows it to pass through the body’s defenses, including the airways and lung tissue, and become absorbed into the bloodstream when inhaled. Once in the blood, PM2.5 can then be linked to health impacts beyond the airways and lungs, such as:

• heart arrhythmias
• developmental and reproductive harm
• cancer
• heart attacks
• stroke

On an annual basis, Oklahoma City averaged a PM2.5 concentration of 9.5 µg/m³ during 2020, thereby meeting the U.S. EPA standard (< 12 µg/m³) but barely passing the more stringent World Health Organization (WHO) standard (< 10 µg/m³). The 2020 annual average was a 4.4 percent (0.3 µg/m³) increase from 2019, when Oklahoma City averaged a PM2.5 concentration of 9.1 µg/m³. This adds to the city’s trend of worsening annual PM2.5 levels since 2016.

An Oklahoma Watch analysis of federal statistics revealed that the number of days considered “unhealthy for sensitive groups” or worse rose to 45 in 2018, up from 20 in 2017, 12 in 2016 and just 5 in 2015.¹

Oklahoma City ranks as the 5th most polluted city for measures of PM2.5 (out of 16 cities) in Oklahoma. The 5 cities that averaged a higher PM2.5 concentration than Oklahoma City include:

• Edmond air quality: 10.0 µg/m³ (11 miles away)
• Broken Arrow air quality: 9.9 µg/m³ (101 miles away)
• Moore air quality: 9.8 µg/m³ (10.7 miles away)
• Tulsa air quality: 9.7 µg/m³ (654 miles away)

On a broader scale, Oklahoma City ranked as the 654th most polluted city in the United States (out of 1,412), with a higher annual average than Denver (8.7 µg/m³), Salt Lake City (7.2 µg/m³), and Phoenix (8.4 µg/m³). The high air pollution ranking indicates that Oklahoma City is falling behind in its battle against air pollution compared to similarly (or larger) cities. More must be done to reduce the pollution burden carried by Oklahoma City residents.

Ozone pollution in OKC

Ozone (O₃) is a highly unstable gas made of 3 oxygen atoms. When inhaled, ozone reacts directly with our lungs and can cause both short-term and long-term health effects, including:

• lung and throat irritation
• chest pain
• shortness of breath
• coughing, wheezing, and increased asthma attacks
• permanent lung damage and reduced lung function
• chronic obstructive pulmonary disease (COPD)

Compared to other air pollutants, ozone is considered difficult to control. Rather than being emitted directly into the air by common emission sources (such as combustion), ozone is formed when precursor pollutants like nitrogen dioxide (NO₂) and VOCs react in the presence of sunlight and heat (generally at temperatures above 84°F). Since ozone is formed from other airborne pollutants, managing its levels requires managing primary pollutant emissions.

Precursor pollutants NO₂ and VOCs are primarily emitted from motor vehicles and industrial activity. While both NO₂ and VOCs are unhealthy to breathe on their own, they become especially harmful when they undergo the chemical transformation into ozone.

Oklahoma City was graded an “F” for high ozone days.² In the last 3 years, 16 days have been classified as “unhealthy for sensitive groups.” According to the American Lung Association’s State of the Air (SOTA) report, Oklahoma County ranks 43rd for high ozone days out of 226 metropolitan areas.

While Oklahoma City has observed significant improvements in ozone levels since 2011, levels worsened during the 2014-2016 and 2015-2017 three-year monitoring periods.

What are the causes of air pollution in Oklahoma City?

Oklahoma City is the capital and largest city of the state of Oklahoma, with more than 640,000 residents. Its air quality is the result of the standard emissions sources, such as motor vehicles, industry, and wood-burning (fires), as well as localized sources and conditions, including:³

• wind-blown dust and dirt from agriculture and livestock (especially during hot and dry summers)
• oil, natural gas, and petroleum-related products and industries

Commuter vehicles represent the leading source of air pollution in Oklahoma City. Recent population increases in historically rural areas underscore a risk for further declining air quality in the city. A report by GreenOKC estimates that each of Oklahoma City’s 227,000 households takes about 10 daily trips (equating to about 2.3 million trips daily in OKC). Vehicle emissions represent a threat to both Oklahoma City’s ozone and PM2.5 levels.⁴

When is the air at its most polluted in Oklahoma City?

Air quality in Oklahoma City varies throughout the year. Air pollution is a much greater concern in the summer when concentrations of both PM2.5 and ozone rise.

Ozone is often associated with summer, as temperatures above or around 84°F are required for its formation and higher temperatures accelerate the formation process. Oklahoma City has a temperate humid subtropical climate prone to hot weather. April through November are Oklahoma City’s “ozone season.”⁵ Between these months, there are approximately 145 days over 80 degrees and 71 days over 90.⁶ On average, 5 days each summer average ozone levels in the “unhealthy for sensitive groups” category.

In Oklahoma City, PM2.5 levels also rise in the summer as a result of:

• seasonal wildfires
• increased power consumption (to cool homes and offices)
• arid conditions that dry land and contribute to windblown dust and dirt

April, June, and July all experienced PM2.5 concentrations above the WHO annual target (< 10 µg/m³), with readings of 10.4 µg/m³, 12.2 µg/m³, and 11.3 µg/m³ (respectively). June notably also exceeded the U.S. EPA target of 12.0 µg/m³.

What are some health problems caused by pollution in Oklahoma City?

Exposure to air pollution can cause a wide array of adverse health effects. While no level of air pollution exposure is deemed completely safe, the likelihood of severe health impacts increases with the length and severity of exposure as well as due to one’s health status. Residents below the age of 18 (children), above the age of 60 (elderly), or living with pre-existing health conditions are more prone to acute effects.

In Oklahoma County, the number of residents living with sensitivities that predispose them to more acute health impacts from air pollution include:

• Pediatric asthma: 19,852 residents
• Adult asthma: 61,125 residents
• COPD: 50,012 residents
• Cardiovascular disease: 63,544 residents
• Age under 18: 202,612 residents
• Age over 65: 111,829 residents

Common health problems from breathing polluted Oklahoma City air quality include:

• lung and throat irritation
• shortness of breath
• coughing and increased asthma attacks
• permanent lung damage and reduced lung function
• heart and lung disease
• cancer
• early death

Even in polluted cities like Oklahoma City, it is possible to breathe clean air year-round. Personal strategies to minimize the effects of air pollution include:

• managing indoor air quality by closing windows and doors and running indoor air filtration, where possible.
• reducing or avoiding unnecessary outdoor activities
• wearing a mask when AQI levels exceed 100
• following Oklahoma City’s AQI forecast to prepare for periods of predicted air pollution

+ Article Resources

[1] Brown T. (2019, July 1). Oklahoma air quality dips after years of steady gains. KGOU.
[2] American Lung Association. (2020). State of the air – 2020.
[3] State of Oklahoma. (2016). Regional haze five-year progress report.
[4] GreenOKC. (2015). Oklahoma City - environment and natural resources.
[5] Wertz J. (2015, October 15). Oklahoma air quality improves as Feds roll out new ozone limits. StateImpact Oklahoma.
[6] Current results. (2021). Oklahoma city temperatures: averages by month.