Another day, another Ozone alert

Denver and the North Front Range missed a deadline to reduce ozone pollution...again. Exceeding ozone air quality limits is bad. However, Colorado is poised to take big actions in the next six months that, done right, could put us on track for the clean air days we deserve.


Another day, another Ozone Alert. The smoke alarm is going off but we’re failing to put out the fire. 

Right now, we’re exceeding ozone pollution air quality limits in an area stretching from Denver through the North Front Range. This is a public health hazard impacting millions of us.

We have the tools to reduce ozone pollution and in the next six months, we can enact a set of policies that bring ozone pollution down.

To underscore the importance of this deadline and the need to act, I joined air quality experts Dr James Crooks from National Jewish Health and Bill Hayes from Boulder County Public Health to dive into ozone nonattainment – what is it, why it matters and why there is hope we can clean up our air.  You can view that webinar here







Ozone Pollution: What is it and where does it come from?

When I was growing up, I remember learning that ozone is really important. There was an ozone hole that threatened to allow dangerous rays to reach our planet and we needed to (and did) reduce the pollutants that were threatening us.

But there is also a bad side to ozone. Ground-level ozone. Dr. Crooks described ozone as the hydrogen peroxide of the air and like hydrogen peroxide we don’t want it on the ground-level where we can breathe it.




Ozone locations – Randy Russell, UCAR




So where does ground-level ozone come from? Ozone isn’t emitted as ozone. It’s a chemical reaction between sunlight (plenty of that in Colorado), oxygen (a little less at our elevation but still plenty to create ozone), and a mixture of pollutants including NOx (nitrogen oxides) and VOCs (volatile organic compounds).

The biggest contributors to ozone in the Front Range are fossil fuel-powered vehicles and the oil and gas sector. Other contributors include large facilities and climate change, which is leading to longer and more extreme fire seasons.







Given the huge amount of forest fire smoke that has been inundating our state over the last few years, it’s easy to blame fires for our ozone problem. But Bill Hayes shared some insight from Boulder County indicating that local ozone sources are still a major cause of our ozone problems.




Wildfire smoke and ozone – Bill Hayes, Boulder County Public Health, CoPIRG webinar, July 20, 2021




Unfortunately, climate change is making ozone pollution worse. When you compare daily ozone to temperatures over the last decade, you see ozone pollution is higher on those warmer days. That makes sense since a key part of the ozone recipe is the sun.

So if we want to reduce ozone pollution, we need to not only tackle the NOx and VOCs that are the primary contributors but the CO2 (carbon dioxide) and methane that fuel climate change. (Sneak peek – there’s a lot of overlap between solutions that reduce ozone pollution and solutions that tackle climate change).




Ozone and climate – Dr. James Crooks, CoPIRG webinar, July 20, 2021




Ozone Pollution: Why does it matter? How will it impact me?

It’s hard not to pay attention when a doctor gives an analogy that ozone is like hydrogen peroxide in the air. That doesn’t sound like something we should breathe. It isn’t.

For decades, ozone pollution was mostly associated with “just” respiratory health concerns. Things like asthma and lung damage.

When I get an ozone alert on my phone the main recommendations are to limit activity outside, especially for people who already have asthma, older adults and children. The piece about children is important because their lungs are still developing so they should not be exposed to dangerous levels of ozone.

But over the last decade, we’ve learned that ozone impacts a number of other diseases. Dr. Crooks highlighted cardiovascular disease, stroke, Alzheimer’s Disease, and diabetes. 




Ozone health impacts – Dr. James Crooks, CoPIRG webinar, July 20, 2021




Ground-level ozone is a public health hazard and given the wide ranging health impacts it should be a top priority for us to cut. So what level do we need to cut ozone pollution to?




Ozone Pollution: A history of missing the mark

The Environmental Protection Agency (EPA) sets air quality standards for ozone pollution. In 2008, they set the level for ozone pollution at 75 ppb.

Unfortunately, Denver and the North Front Range (DM/NFR) missed it. Not just in 2008 but every year since then.

Every few years, the EPA checks back in with us and, if we haven’t met the 75 ppb level, they bump us up a nonattainment scale – first it was “marginal” then “moderate” and now we’re in “serious” going on “severe” nonattainment.

Each time we’re bumped up the scale, our Regional Air Quality Council (RAQC) is then supposed to develop a new plan (State Implementation Plan or SIP) and to develop additional programs and regulations to reduce pollution.

But is 75 ppb even the right level? Well, over time, the EPA has lowered the standard. It started at 80 ppb. Then in 2008 they lowered it to 75 ppb. In 2015, they lowered it again to 70 ppb. It’s confusing because we’re still struggling to meet the 75 ppb (in fact we missed another deadline on Tuesday) not to mention the new, lower 70 ppb level.




History of ozone nonattainment – Bill Hayes, Boulder County Public Health, CoPIRG webinar, July 20, 2021




What’s clear is we’re not where we need to be. The smoke alarm has been blaring for over a decade and we haven’t done what we need to do for it to go off.

The good news is we could have just removed the batteries and ignored the problem. We didn’t do that.

We’ve made some progress. As you can see on the slide below, our ozone pollution has gone down slightly over time. But below that line you can see we’re still well above the air quality levels set in 2008 and in 2015 (the blocks) and our nonattainment status is getting worse.




Progress on ozone pollution – RAQC presentation to AQCC, data through 10/30/20




Six actions in the next six months can cut ozone pollution

To reduce ozone pollution we must tackle the two largest contributors to ozone in the Front Range – transportation and oil and gas.

You’ll notice some of the actions coming up are focused on greenhouse gas emissions but so often the same strategies that reduce greenhouse gas emissions (like switching from a gas-powered vehicle to an electric vehicle) cut climate pollution and ozone pollution.

The ozone solutions fall into a couple of categories:

  • Give people better options to get around so we don’t always have to drive our car to complete trips. Options include better bus service, teleworking options, and access to safe biking and walking infrastructure.
  • Convert the vehicles we do have on the road to tailpipe free, electric-powered vehicles. Tailpipes are where a lot of the pollution comes from.
  • Cut pollution from oil and gas drilling in Colorado.

Here are six major actions (OK, one is a bunch of little actions) that are happening in the next six months that, if done right, will bring ozone pollution down.

  • Employer-based Trip Reduction Program – The Air Quality Control Commission (AQCC) is currently considering the Employer-based Trip Reduction Program (ETRP). The rule would help reduce pollution from vehicles by expanding options for employees to commute without driving alone every day. Options could include more teleworking, better access to transit with bus passes, carpool programs and amenities that help people walk and bike more. The rule will be decided at the AQCC’s August 18-20 rulemaking hearing.
  • CDOT Greenhouse Gas Pollution Standard – This fall, the Colorado Department of Transportation (CDOT) will consider rules around reducing greenhouse gas emissions in the transportation sector. Transportation is the largest source of greenhouse gas emissions in Colorado, a leading contributor to climate change and the forest fires that contribute to ozone. Reducing greenhouse gas emissions in transportation would also result in less vehicle-emitted ozone pollutants. A decision is expected by the CDOT Transportation Commission later this fall.
  • Implementation of Xcel’s Transportation Electrification Plan (TEP) – Electric vehicles produce zero tailpipe emissions and are an important way to reduce ozone pollution. Over the next three years, Xcel Energy will invest over $110 million in vehicle electrification strategies that could speed up the transition to cleaner vehicles. Much of Xcel Energy’s territory overlaps with parts of the state that failed to meet the ozone standard. Xcel is making decisions now on how they will invest in electrification.
  • Oil and Gas Greenhouse Gas Rulemaking Effort – The Air Quality Control Commission (AQCC) is expected to kick off a rulemaking in September to reduce greenhouse gas emissions in the oil and gas sector. The commission is considering several strategies including improving equipment and processes, reducing the greenhouse gas intensity and overall emission reduction programs. More information here.
  • Adoption of Cleaner Truck Rules – Colorado’s Greenhouse Gas Pollution Reduction Roadmap envisions a rulemaking at the AQCC in 2022 to adopt new rules to clean up trucks, including cutting tailpipe pollution and transitioning to electric-powered heavy-duty vehicles. There are several options other states are pursuing. An initial state-sponsored study should be completed this summer and the AQCC could take up the rule as soon as this November.
  • Municipal Government Actions – Cities and counties can play a big role in reducing ozone pollution. Every year, municipalities make lots of decisions around how to spend millions of transportation dollars and how to guide development. Focusing transportation spending and development in ways that support walking, biking and transit are often overlooked solutions to our ozone pollution problems.

To underscore the importance of ensuring we get these actions right, just this week, the Polis Administration indicated that they will propose gutting the first action up – ETRP.

In a statement released during a pre-hearing, the administration said they would propose removing all of the pieces of the rule that would result in real pollution reductions, leaving in place a simple survey of employee trip patterns.

This action, coming the same week that we missed yet another major ozone pollution reduction deadline, is extremely disappointing.

It highlights the importance of the work we do – educating, organizing and advocacy – so we can lift up the public voice and ensure that our state and local officials hear that ozone smoke alarm calling for immediate and concrete action to put out the fire.



Danny Katz

Executive Director, CoPIRG

Danny has been the director of CoPIRG for over a decade. Danny co-authored a groundbreaking report on the state’s transit, walking and biking needs and is a co-author of the annual “State of Recycling” report. He also helped write a 2016 Denver initiative to create a public matching campaign finance program and led the early effort to eliminate predatory payday loans in Colorado. Danny serves on the Colorado Department of Transportation's (CDOT) Efficiency and Accountability Committee, CDOT's Transit and Rail Advisory Committee, RTD's Reimagine Advisory Committee, the Denver Moves Everyone Think Tank, and the I-70 Collaborative Effort. Danny lobbies federal, state and local elected officials on transportation electrification, multimodal transportation, zero waste, consumer protection and public health issues. He appears frequently in local media outlets and is active in a number of coalitions. He resides in Denver with his family, where he enjoys biking and skiing, the neighborhood food scene and raising chickens.