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Smog from forest fires in northern Alberta obscures areas of downtown Denver May 22, 2023. The Canadian smoke added to Denver's existing ozone problems and created high pollution warning days for the Front Range. (Olivia Sun, The Colorado Sun via Report for America)

Call it Sheboygan Syndrome: the inability year after year to meet the ozone health standard for air quality despite enacting controls decade after decade. And the question for the Front Range is does it have a bad case of the ailment?

About 22 metropolitan areas — large and small, including a large chunk of California and the East Coast — failed to meet the first ozone standard issued by the federal Environmental Protection Agency in 1979 and have been failing ever since.

A few in the interim managed to meet an ozone standard only to fall back into noncompliance when the EPA lowered the acceptable exposure level for the corrosive gas, which is created when pollutants interact with sunlight and heat.

“It is a real challenge,” said Will Barrett, national senior director for clean air advocacy at the American Lung Association. “It does take time and it does take planning and implementation and enforcement. In some cases, it can take what feels like a lifetime.”

There have been successes and the number of areas out of compliance with the most recent standard is 47, covering 189 counties, down from 63 areas and 219 counties in 1990, according to EPA data.

“Things have improved overall, the nation’s air has gotten cleaner,” said Seth Johnson, a senior attorney with Earthjustice, a nonprofit environmental law group. “The ozone problem has gotten more concentrated.”

So, the question for the nine-county Front Range nonattainment area — where health ozone alerts were issued for seven of the last nine days — is whether it is an Atlanta, which came into ozone attainment this year, or a 26-year ozone offender like Sheboygan, Wisconsin?

“We can do this,” said Mike Silverstein, executive director of the Regional Air Quality Council, which oversees Front Range ozone monitoring and the plans to get back into compliance.

“In the ’70s and ’80s, we had infamous air quality issues,” Silverstein said. “We had great success reducing emissions from vehicles, street sanding, we did what we needed to do and by the mid-’90s we achieved all the air standards.”

But the ozone standard was lowered in 1997 and the region was back on the noncompliance rolls in 2004 and has been there for the past 19 years.

“We aren’t close to being in compliance,” said Robert Ukeiley, a senior attorney with the Center for Biological Diversity, a nonprofit environmental group.

“There are three steps to getting to cleaner air: making rules, implementing the rules with permits and enforcing the rules,” Ukeiley said. “So far, they’ve done the first step nine or 10 times, but haven’t gotten much farther.”

Air is cleaner now and health impacts of ozone are more evident

So, is it to be Atlanta or Sheboygan?

Sheboygan is a city of 50,000 on the shores of Lake Michigan about 60 miles north of Milwaukee. It met the EPA’s first ozone standard, issued in 1979, of no more than 120 parts per billion of ozone in the air over one hour.

However, like Denver when the standard was changed in 1997 to an average of 80 ppb over eight hours, the city fell into noncompliance. Since then, EPA has lowered the eight-hour standard, which is a protective health standard under the Clean Air Act, to 75 ppb in 2008 and 70 ppb in 2015.

Why the continual ratcheting down? “As the air has gotten cleaner, we’ve been able to detect health impacts at lower and lower levels,” said James Crooks, an epidemiologist at National Jewish Health.

Crooks said that in addition to epidemiological studies that looked at the health impacts of ozone on large populations, laboratory experiments have given researchers a better understanding of the ways the gas can damage the human body.

On June 9, the EPA’s Clean Air Scientific Advisory Committee said new studies were showing “airways effects” at 60 ppb and recommended the standard be lowered to 60 to 55 ppb.

Sheboygan exceeding the ozone limit triggered an EPA-required series of steps, such as creating an auto emissions inspection program, referred to as I&M, and requiring controls on major pollution sources. All to no avail.

A cutleaf coneflower plant in an ozone monitoring garden near NCAR in Boulder developed “stipples” on its leaves indicating too much exposure to ground-level ozone. (Nina Riggio, Special to The Colorado Sun)

“Wisconsin’s Lake Michigan shoreline areas, including Sheboygan, have struggled to attain and maintain federal ozone,” Craig Czarnecki, a spokesman for the Wisconsin Department of Natural Resources, said in an email.

“Several factors are responsible for this,” Czarnecki said. “First, high-ozone air tends to accumulate over Lake Michigan on hot summer days, which then moves into Wisconsin shoreline counties through natural lake breezes. In addition, Wisconsin is downwind of large urban areas (like Chicago) whose emissions get transported into the state.”

The state air models indicate that Wisconsin sources are responsible for less than 10% of the ozone at its monitors. Nor does the state have much control over the cars and trucks moving along its highways.

“Taken together, these factors significantly challenge Wisconsin’s ability to, on its own, attain EPA’s ozone standards by Clean Air Act deadlines,” Czarnecki said.

The most intractable and severe problems have been on the coasts. In California, 21 areas from San Diego to San Francisco to Lake Tahoe are at some level of noncompliance with the 2015 ozone standard, according to EPA data.

“The California Air Resources Board has been in existence for 50 years … so we’ve been battling this for a long time,” said Michael Benjamin, chief of CARB’s air quality and science division.

“We’ve had a lot of success, but the most challenging region is the South Coast Air Basin, the Los Angeles area,” Benjamin said. The basin and California’s San Joaquin Valley are the only two areas in Los Angeles County in “extreme” nonattainment.

Curbing the emissions that create ozone

California has been a leader in trying to curb pollution by reducing the so-called precursors of ozone — volatile organic compounds, or VOCs, and oxides of nitrogen, or NOx.

When NOx and VOCs mix with heat and sunlight — both of which Los Angeles has in abundance — it creates ozone.

“In the 1980s, there was a lot of focus on VOCs,” Benjamin said, cracking down on emissions from industry to the local filling station.

A decade earlier the state had been the first to require catalytic converters — which destroy both hydrocarbons and NOx — on new cars. It is now a national standard.

Since the 1990s VOC emissions in the South Coast basin have dropped by two-thirds to 400 tons per year and NOx emissions three-quarters to 350 tons per year.

 “Do we see a proportional decline in ozone?” Benjamin asked. “The short answer is no.”

Still, since the 1990s the basin’s design value for ozone (a sort of average of averages) dropped to 100 ppb for eight hours in 2015 from 180 ppb in the 1990s. (Denver’s current design value is 83 ppb).

Progress, however, stalled around 2015. At first air regulators were puzzled, but eventually found that there had been a shift in the region’s ozone chemistry to an emphasis on NOx emissions.

Transportation accounts for 80% of California’s NOx. The CARB has issued a zero-emission vehicle rule, to increase the sale of electric and other nonpolluting vehicles. It also has issued a clean truck rule, a clean fleet rule and a rule requiring electric garden equipment, such as lawn mowers and leaf blowers.

Jordan Champalou demonstrates an electric DeWalt electric leaf blower Dec. 1, 2022, near Sloans Lake. Champalou has been mowing lawns since age 10 and now maintains 30 to 40 residential properties per week using all electric lawn tools. (Olivia Sun, The Colorado Sun via Report for America)

Colorado has adopted versions of California’s zero-emission vehicle rule and its clean truck rule. The Colorado Air Quality Control Commission will consider an electric lawn and garden equipment rule in December.

The region is once again making progress, Benjamin said, but it is going to require an additional 80% reduction in NOx over the next 15 years.

Some major sources — ocean-going vessels, airplanes and locomotives — are beyond state control, Benjamin said, being regulated by the EPA or international accords.

The hope is that there will be ways to reduce emissions from these sources. “The only way we can get there is moving away from combustion of fossil fuels,” Benjamin said.

No pollution is local

On the East Coast, metropolitan areas from Boston to Washington, D.C., have been wrestling with ozone for decades and sharing pollution among themselves. They are all linked by the busiest highway in the country, Interstate 95.

“The Clean Air Act requires each area to meet the ozone standard within its boundaries, which is really difficult here,” said Joseph Minott, executive director of Philadelphia-based Clean Air Council, a nonprofit advocacy group.

This has led to a circular firing squad of complaints to EPA from states arguing that unless other states reduce their pollution they cannot meet the ozone standard.

Pennsylvania complained about Ohio. New Jersey complained about Pennsylvania. Maryland complained about West Virginia. New York filed a complaint against nine states, including Indiana, Illinois and Michigan.

In March, the EPA issued its Good Neighbor Plan, aimed at securing significant reductions of NOx from power plants and industrial facilities across 23 states.

Most of the states in the plan are in the East and Midwest stretching down to Texas, but Nevada and Utah are also included, as EPA says Utah is sharing its pollution with Colorado.

Minott said all the big emitters in the Philadelphia region have been addressed. “One of the biggest sources of pollution was the old Sunoco refinery, but it blew up in 2019,” he said. “Now we are chasing smaller and smaller sources.”

Still, there is progress. In 2015, seven areas — including Atlanta, Louisville, Cincinnati, Detroit and Columbus, Ohio — were reclassified as in ozone attainment.

Atlanta’s journey to ozone attainment took 35 years

How did Atlanta do it?

Atlanta was in violation from the very first and has been working at curbing pollution for more than 35 years. 

“We did all the major things — like enhanced I&M for autos — and a lot of little things,” said James Boylan, chief of the air protection branch of the Georgia Environmental Protection Division.

And the region was steadily making progress, with 20 counties in violation of the 1997 standard, 15 counties in violation of the 2008 standard and five counties in violation of the 2015.

As ozone pollution controls went into effect across the country, Boylan said, there was less transport from other states, which helped. “It used to be when one monitor went off, they all went off,” he said. “But over time what had been a regional problem became a local problem.”

Some trends also helped. Cars became cleaner as old ones were replaced with new, more efficient models and controls were placed on the region’s coal-fired power plants, and some even closed.


Stricter permitting for new sources of emissions may have also kept some large industrial projects out of Atlanta, Boylan said.

Then there were a host of targeted initiatives. Norfolk Southern and CSX both have large rail yards in Atlanta and in a voluntary program 50 old and dirty yard locomotives were replaced with clean diesel or propane engines.

The city used part of its share of the 2016 federal lawsuit settlement with Volkswagen, which had systematically cheated on emission tests, to replace its buses with cleaner models.

Over the past 30 years NOx emissions decreased by 68% and VOCs by 57%.

“What pushed us over the finish line was changes from the COVID pandemic,” Boylan said.

Two of the metropolitan area’s biggest sources of NOx are vehicle traffic and the Hartsfield-Jackson Atlanta International Airport, the world’s busiest.

When the pandemic hit, pollution from both dropped and when activity returned it was not at prepandemic levels. “We were anxious to see how we would fare in 2021 and 2022,” Boylan said. “We’ve  stayed below the standard.”

“We started out with a bad problem and there were a lot of things we were forced to do and then we took some initiatives on our own,” he said.

Wildfire smoke is not a controllable factor

Detroit also came back into compliance this year, but not without controversy over an issue that may also become a big factor for Denver — wildfire smoke.

The Michigan Department of Environment, Great Lakes, and Energy sought and the EPA granted a waiver to toss out two daily high readings in June 2022 at one of its ozone monitors due to wildfire smoke from Canada.

Vehicles commute on U.S. 24 outside Hartsel amid the low visibility due to the plumes of smoke in the sky on May 23. The smoke was drifting into Colorado and other states from massive wildfires in Canada. (Hugh Carey, The Colorado Sun)

The way compliance is calculated is a three-year average of the fourth-highest reading at monitors. Tossing out those two readings meant they were replaced with lower readings.

The Great Lakes Environmental Law Center challenged the state’s requests for “an exceptional event.”

“We don’t believe that the ozone data at the monitor was impacted by wildfire smoke on those two days,” said Nick Leonard, the law center’s executive director. “Regardless of whether there was smoke there or not, this monitor is located in a predominantly Black community with above-average asthma rates.”

“If they didn’t get this waiver they would have taken additional steps to reduce pollution, particularly in this vulnerable community,” Leonard said.

Wildfire smoke, however, is seen by air quality regulators as a new and confounding element in meeting ozone compliance.

It is something they cannot control and may actually mask the progress they are making.

“It is super complicated to assess the impact of regional smoke, and to gain an exceptional event,” Silverstein said. “It is going to be very important to make those determinations in the coming years.”

“The entire West is working collaboratively to come up with a model to assess wildfire smoke,” he said.

Of course, getting a waiver may improve the ozone average, but it doesn’t make the air cleaner. “There can be a disconnect from the legal requirements and what people are experiencing,” said Benjamin, the California air quality manager.

Challenging a request for a wildfire smoke event may also be difficult for clean air advocates because the filings are very technical, Leonard said.

The 2008 ozone standard is still on the books so the Front Range has to meet it as well as the 2015 standard.

The deadline for meeting the 2008 75 ppb standard is this year. “We all know there is no way we will get there,” Silverstein said. “We expect the EPA to downgrade us to severe and that will push attainment to 2027.” (Chicago reached attainment for the 2008 standard this year, but still has to meet the 2015 level.)

This will mean that the target date for both the 2008 and 2015 standards will be 2027.

Silverstein said that new rules tightening emissions on oil and gas operations, small stationary engines and lawn and garden equipment are coming and rules already adopted will continue to whittle away at emissions.

The Center for Biological Diversity’s Ukeiley remains skeptical, saying that tightly written permits and even tighter enforcement are needed.

So it remains to be seen whether the Front Range is an Atlanta or a Sheboygan. There are, of course, some confounding vagaries when it comes to ozone pollution.

Some 29 miles north of Sheboygan is Manitowoc. This year Manitowoc County was redesignated as in compliance with the federal ozone standards. What magic was worked in Manitowoc County that eluded Sheboygan?

“There are no meaningful differences between Sheboygan and Manitowoc when it comes to the causes of the ozone measured in those areas or how much control they have over it,” Wisconsin’s Czarnecki said.

Special to The Colorado Sun
Twitter: @bymarkjaffe