The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (40 CFR part 50) for six principal pollutants ("criteria" air pollutants) which can be harmful to public health and the environment. The Clean Air Act identifies two types of national ambient air quality standards: Primary and Secondary. Primary standards provide public health protection, including protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.(link)

In 2012, U.S. EPA established the primary NAAQS for the pollutant, PM2.5, as 12.0 ug/m3 as annual arithmetic mean, averaged over 3 years (PM2.5 annual NAAQS), and as 35 ug/m3 as 98th percentile, averaged over 3 years (PM2.5 daily NAAQS). In 2020, U.S. EPA re-adopted the PM2.5 annual and daily NAAQS set in 2012 with no changes. In 2024, U.S. EPA revised the primary PM2.5 annual NAAQS to 9.0 ug/m3 as annual arithmetic mean, averaged over 3 years, and retained the other PM2.5 standards without revision. This new PM2.5 standard goes in effect on May 6, 2024. (link)

This indicator is for the PM2.5 annual standard. CCPH Air Pollution Control (APC) Division continuously measures PM2.5 in the ambient air year round to determine compliance with the PM2.5 annual NAAQS at 2 locations in Stark County: Canton Health Department and Canton Fire Station 8. As an indicator, APC chose to use the quarter average concentration of PM2.5 each quarter, which is a shorter averaging period than used for the PM2.5 annual NAAQS (annual arithmetic mean, averaged over 3 years) and is able to show seasonal changes. 

APC also operates intermittent filter-based sampler equipment to measure PM2.5 once every 3 days at those 2 locations. The collected filters require external laboratory analysis to quantify the PM2.5 value causing the data from this equipment to not be available for a month or more after it is collected. Since this data is delayed, it is not used for the indicator.

Explanation of exceedances:

2nd Quarter 2025 exceedances: In early June 2025, the PM2.5 was higher due to Canadian wildfires, over which APC has no control, causing the entire 2nd quarter to be elevated. June also had several community fireworks displays that likely contributed to the elevated PM2.5. Even though this quarterly average is above the PM2.5 annual NAAQS value, the average of the 1st and 2nd quarters was equal to the annual NAAQS value, showing the data is likely not an exceedance of the NAAQS, which is based on annual data average over 3 years including the intermittent and continuous data.

4th Quarter 2024 exceedances: In early October and late October, the PM2.5 was higher due to NW USA and Oklahoma wildfires, respectively, over which APC has no control, causing the entire 4th quarter to be elevated. Even though these quarterly averages were above the PM2.5 annual NAAQS value, they were likely not an exceedance of the NAAQS, which is based on annual data average over 3 years including the intermittent data. The PM2.5 NAAQS annual value was lowered on May 6, 2024 and Ohio EPA has submitted their designation recommendations to U.S. EPA in on February 4, 2025, and then supplemented on April 9, 2025, asking for Stark County to be attainment using 2022-2024 data with the exceptional events due to wildfires data excluded since the data shows the area as equal to or less than the 9.0 standard.

3rd Quarter 2024 exceedances: These exceedances are mostly attributed to the Canadian wildfires and other States wildfires, over which APC has no control, and also attributed to fireworks during summer events. Even though these quarterly averages were above the PM2.5 annual NAAQS value, they were not an exceedance of the NAAQS, which is based on annual data average over 3 years, including the intermittent data. 

2nd Quarter and 3rd Quarter 2023 exceedances: All of these exceedances are attributed to the Canadian wildfires, over which APC has no control. Even though these quarterly averages were above the PM2.5 annual NAAQS value, they were not an exceedance of the NAAQS. The averaging period for the PM2.5 annual NAAQS of an annual arithmetic mean, averaged over 3 years was determined for 2021-2023 to equal 9.90 showing compliance with the 2012 PM2.5 annual NAAQS that was applicable during 2023. 

Ohio EPA

U.S. EPA - Airnow.gov [live data is shown here]

The Clean Air Act requires states to develop a general plan to attain and maintain the standards in all areas of the country and a specific plan to attain the standards for each area designated nonattainment. These plans, known as State Implementation Plans or SIPs, are developed by state and local air quality management agencies and submitted to EPA for approval. Ohio's SIP can be found here. For PM2.5, Ohio EPA's SIP generally comprises of regulations to control emissions of particulate pollutants.

Stark County has been in compliance with the 2012 PM2.5 annual NAAQS and 2012 PM2.5 daily NAAQS, and officially designated by U.S. EPA as in attainment in 2015. For the new 2024 PM2.5 standard, Ohio EPA has completed their draft designation recommendations to U.S. EPA in November 2024 asking for Stark County to be unclassifiable using 2021-2023 data due to not having enough data when 2021 year is included and since the area will be in attainment using 2022-2024 data. U.S. EPA will make the final designations for the new 2024 PM2.5 annual NAAQS in 2026.

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