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End of 2023 ozone season shows meaningful progress for air quality, with more work to be done

Published: September 11, 2023

Ground-level ozone remains the Front Range’s most pressing air quality problem. The human-caused emissions that combine to form this invisible, odorless pollutant in the heat and sunshine of beautiful Colorado days come mainly from diesel and gas-powered vehicles, gas-powered lawn and garden equipment, and oil and gas production.  

“Ozone season” in Colorado therefore runs from each June through August, the three months of the year with the highest ground-level ozone levels. While May or September can include a few days with higher levels of ozone, it’s unlikely the Front Range will have additional high ozone days this year.  

2023 has shown meaningful progress towards improving the state’s air quality and reaching attainment for both national ozone standards set by the Environmental Protection Agency (EPA). In 2023, the Front Range experienced: *  

  • – The fewest “Ozone Action Alert Days” since 2019. These days are called as a preventative measure by the Colorado Department of Public Health and Environment (CDPHE) when high ozone levels are forecasted on a given day after 4 p.m. or for the next day before 4 p.m. The CDPHE called 38 Ozone Action Alert Days in 2023, compared to 43 in 2020, 73 in 2021, and 46 in 2022.  
    • – From June 1 through August 31—the official ozone summer season—CDPHE called 37 Ozone Action Alert Days in 2023, compared to 43 in 2020, 65 in 2021, and 40 in 2022.  
    • – One Action Day was called in early September 2023. 
  • – The fewest violations of the less stringent, 2008 EPA 75 ppb standard since 2019: 9 exceedances. Only one monitoring location registered four exceedances (the threshold to be out of attainment). All others had three or fewer this calendar year. 
  • – The fewest violations of the stronger, 2015 EPA 70 ppb standard since 2019: 26 exceedances. 6 of 15 monitoring locations showed 3 or fewer exceedances, an improvement from only 3 of 15 in 2022, and zero monitors in 2021.

*These numbers are based on raw data and have not yet been finalized by the Colorado Air Pollution Control Division (APCD).  

The improvements can be attributed to an array of combined factors: increased public awareness and individual actions (such as combining car trips, reducing vehicle idling, and working from home), large scale public transit efforts during the peak ozone months of July and August by multiple agencies (such as “Zero Fare for Better Air”), voluntary vehicle and equipment electrification, regulatory efforts to require lower emission rates, and more.  

Weather with cooler days and more rain also created atmospheric conditions less likely to form higher ozone levels. Wildfire smoke that travels longer distances, such as from the widespread Canadian wildfires this year, can have more of an impact on ground-level ozone creation than local fires, which mostly produce particulate matter and is less likely to create higher ozone along the Front Range.  

While ozone levels are improving, there is still more work that needs to be done. The RAQC is rolling out new and larger projects ahead of the 2024 ozone season.  

The summer ozone seasons from 2024 through 2026 in the Denver Metro / North Front Range region are also an important timeframe to measure ozone levels. The National Ambient Air Quality Standards (NAAQS) include this three-year monitoring data window to analyze whether our region is in attainment. To reach attainment, each of the monitoring sites in our region must record a 4th highest daily ozone value—averaged over those 3 years—of less than or equal to the standard.  

Regulatory Proposals 

  • – The RAQC has forwarded a proposal to the Air Quality Control Commission (AQCC) to limit the use of gas-powered lawn and garden / parks equipment by public entities and commercial companies, as well as banning the sale of residential gas-powered small equipment within the nonattainment area, which will phase out the use of high polluting equipment. 
  • – The RAQC is forming additional regulatory proposals for the Oil and Gas industry, which will also be forwarded to the AQCC by the end of the year.

Public Awareness and Collective Action

  • – Simple Steps. Better Air., the RAQC’s signature public engagement campaign, partnered with over 50 media outlets in 2023, expanded in-person tabling at area events, supported and promoted partner efforts like “Zero Fare for Better Air,” increased the number of recipients who receive email and/or text ozone alerts, and improved engagement and awareness of ground-level ozone in-person and online.  
  • – The residential Mow Down Pollution program—which provides individuals who recycle old gas-powered lawn equipment with $75 or $150 vouchers (based on the item recycled) and $75 vouchers for residents who don’t own gas equipment, to purchase new electric or manual lawn equipment—issued over 2,300 vouchers to individuals in 2023, with more than double the funding in the program than was spent in 2022.

“Collective action can and will continue to make a meaningful difference in reducing ground-level ozone. Roughly half of ozone precursors come from industry, but the other half come from all of us: driving gas vehicles, using gas lawn equipment, and burning other fossil fuels,” said Kelsey Simpkins, Communications and Programs Coordinator for the RAQC. “Individuals are not only half the solution to reducing this invisible air pollutant, but it’s also their health and that of their communities here in the Front Range which will benefit.”

Large Scale Programs 

  • – Mow Down Pollution (Local Government), is awarding over $1.2 million in grants to local governments to electrify parks equipment, with over half of those funds already awarded. 
  • – Charge Ahead Colorado has distributed over $400,000 for EV infrastructure in 2023, expanding charging options across the Front Range.*  
  • – Alt Fuels has distributed over $4.5 Million towards electric vehicles, replacing diesel vehicles that are being scrapped.*

*These programs are phasing out as the state is doing additional work in this area. The RAQC is proud to have run these programs successfully and for the state to take on that work at a larger scale.

2024 Programs 

In 2024, the RAQC will be rolling out a slew of new and larger programs aimed at direct ozone reduction efforts, including:  

  • – Applying $600,000 to the Mow Down Pollution programs, as part of a September 2023 Supplemental Environmental Program (SEP) settlement related to Suncor air quality violations. 
  • – Residential lawn and garden equipment exchanges in communities close to the Commerce City Suncor facility.  
  • – Additional funding to local governments electrifying parks and other equipment at scale. 
  • – Anti-idling campaigns, targeting reductions in both commercial vehicle idling across the region and passenger vehicle idling near schools. 
  • – Employer micro-grants to support businesses who encourage employees to take alternative transportation or increased work from home. 
  • – Auto Maintenance and Repair programs that provide no-cost repairs for older vehicles that have or likely will fail emissions tests. 
  • – Increased community marketing and engagement, including new hyper-localized efforts.

The RAQC will also continue reporting progress on reaching the ozone standards with monitoring data collected by the APCD, conduct studies to update and improve emissions estimates for control strategy evaluation, improved ozone modeling, emissions source tracking, analytical support for other organizations, and the like.

Media contact: Kelsey Simpkins, Communications and Programs Coordinator.