Hazy and polluted air over the Denver skyline as seen from Speer Boulevard
As traffic rolls along Speer Boulevard in the foreground, the skyline is shrouded as pollution fills the air Wednesday, March 6, 2019, in Denver. (AP Photo/David Zalubowski)

The World Health Organization says areas like Colorado’s Front Range counties need stringent new air pollution limits, firing a daunting challenge at Colorado leaders already scrambling to catch up to less-onerous restrictions imposed by the EPA. 

The new WHO guidelines released Wednesday, developed by hundreds of scientists around the world, including Colorado State University environmental epidemiologist Dr. David Rojas, would put Colorado even further from attaining air pollution limits that Front Range counties have been failing for years.

On ozone, for example, which plagued the Front Range this past hot and smoky summer, WHO says peak season readings should be no more than 60 parts per billion. The Front Range “nonattainment area” for EPA ozone guidelines routinely broke that limit all summer. State planning agencies such as the Regional Air Quality Council are currently drawing up new pollution-restriction policies to get Colorado’s ozone peak averages under EPA limits of 70 parts per billion

For PM2.5 particulate matter, often caused by wildfire smoke and dust on the Front Range, the WHO is recommending that governments cap pollution at 15 micrograms per cubic meter, compared to the EPA’s current 24-hour average level of 35.  

WHO has no direct control over U.S. or state air pollution policy, but the report lends more credence to Colorado scientists and environmental groups who have been calling on the state Air Pollution Control Division to move faster in tackling pollution sources. National Jewish Health researcher Jim Crooks, among many, has been arguing that an ozone cap of 65 would be best for Coloradans’ lung health. 

In the past month, Rojas said, Denver had only four or five days that were below the new WHO guidelines for PM2.5 readings. 

“We are not in a good spot,” he said. 

State air pollution officials noted that ozone is the only monitored pollutant where the Front Range is out of compliance with current EPA guidelines. As for WHO’s admonition to further tighten all pollutant limits to protect health, state health department spokesman Andrew Bare said officials were still reviewing the report. 

“We agree with the importance of minimizing air pollution, including for particulate matter, and we will continue to pursue policies to reduce air pollution and provide Coloradans with clean air to breathe,” Bare said in an emailed statement. 

“The guidelines underscore that ozone at the levels recorded in the Denver Metro/ northern Front Range ozone nonattainment area constitute a public health crisis, and more has to be done sooner to reduce emissions,” said Joro Walker, Western Resource Advocates’ general counsel for air quality, after reading an embargoed copy of the WHO report. 

EPA staff scientists recommended cuts to allowed levels of PM2.5 during the Trump administration, but top agency officials rejected the idea, said Robert Ukeiley, Colorado counsel for the Center for Biological Diversity. Since the Biden administration took over, the EPA announced it would indeed review the standards with an eye toward lowering them. 

“I am hopeful that WHO’s decision to lower its PM2.5 air quality guidelines to significantly below the U.S. standards will influence the EPA,” Ukeiley said. 

Rather than dismiss the WHO guidelines as too radical for practical change, Rojas said, Colorado officials should embrace them as an opportunity. Policies that attack air pollution in Colorado are an automatic two-fer, Rojas explained — the same policy measures that could reduce ozone or PM2.5, like reducing the number of miles driven or cutting oil and gas leaks, also drive down greenhouse gas emissions toward state goals. 

“So many different interventions that are required for climate change will have an impact on air quality,” he said. 

In fact, many conservation groups say, attacking air pollution can be a triple winner, since communities of color and lower-income neighborhoods have been shown to be more vulnerable to both pollution and COVID-19’s devastating respiratory impacts

Since it last revised the air pollution guidelines in 2005, WHO said in its report, there has been a “marked increase” in the evidence showing that health impacts from pollution are greater than previously thought, and occur at lower limits than previously known. High-income countries have improved their air, but still exceed even the 2005 guidelines for many pollutants. 

In low- and middle-income countries, meanwhile, increased urbanization, growth of coal-fired power plants in developing nations, and desertification of land around Africa’s Sahara have all contributed to deterioration of the air. WHO estimates more than 90% of the world’s population lives where PM2.5 concentrations exceed the organization’s 2005 guidelines, and that total will now increase with lowered recommendations.

Front Range counties have worked with state officials and conservation groups for decades to control ozone, PM2.5, sulfur dioxide and other EPA-regulated pollutants. Bans on most home wood burning and boosts to street sweeping help cut back on PM2.5. Equipment regulations on oil and gas production are meant to cut into emissions of methane and volatile organic compounds that contribute to ozone and greenhouse gases. 

The next rounds of regulation needed to bring the Front Range back into EPA attainment could involve requiring cleaner-burning fuel mixes in vehicles, further electrification of cars and home appliances to run on clean energy, and more caps on the highest-polluting industries. Wildfire smoke from distant states or even Canada amped up PM2.5 in the summer, and the state can’t control that, but conservation groups say that means regulators need to crack down harder on local sources that can be tamed. 

“I’d like to incentivize more electric vehicles, but also incentivize public transportation,” Rojas said. 

“The new guidelines should serve as another wake-up call to Colorado state regulators and lawmakers following a summer with record-high ozone action alert days, and heavy particulate matter pollution that has blanketed much of the state for months,” said Walker. 

Michael Booth is The Sun’s environment writer, and co-author of The Sun’s weekly climate and health newsletter The Temperature. He and John Ingold host the weekly Sun-Up podcast on The Temperature topics every Thursday. He is co-author with...