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Colorado's Air Is Unhealthy Right Now. Check The Air Quality Index Before Venturing Outside

A hazy Denver skyline is just one impact of poor air quality.
Dennis Schroeder
A hazy Denver skyline is just one impact of poor air quality.

In recent weeks, Colorado’s air quality has rapidly deteriorated. Smog, a portion of which is composed of smoke from wildfires within and outside the state, has obscured our view of the mountains from the Front Range. And this week the state failed to meet an Environmental Protection Agency deadline for reducing ozone pollution.

Both ozone and smoke are bad for our health, but monitoring air quality can help regulators and the public make better decisions. That is, if the readings are precise enough.

An ozone breeding ground

Ozone is a secondary pollutant, so it isn’t emitted like some other gases, like carbon dioxide. It forms when exhaust materials released by cars and oil and gas production enter the air and chemically react in the presence of sunlight.

Although a layer of ozone in the upper atmosphere protects Earth, ground-level ozone is harmful. It’s also clear, so it can be difficult to evaluate air conditions by eye. And Boulder County Public Health air quality program coordinator Bill Hayes says Colorado is uniquely situated for high ozone levels.

“At higher elevation, we get greater solar irradiance than they do at sea level. So more energy to drive the reaction,” he said. “And then because of our topography, those ozone precursors often get trapped up against the foothills, up against the mountains.”

In 2008, the Environmental Protection Agency set a national ozone standard at 75 parts per billion. The deadline to reach that goal was July 20, and parts of Colorado still haven't made the cut. But that’s not the end of the story: the EPA lowered the standard even further in 2015, from 75 to 70 parts per billion.

“There is no safe level for ground-level ozone,” said Hayes. “So we actually expect that 70 parts per billion to keep being lowered to really make it a health-based standard.”

Odorless smoke is still harmful smoke

Like ozone, smoke poses numerous health risks because of tiny particles that can enter the lungs. It’s especially bad for people with respiratory conditions like asthma and COPD. High air pollution levels have also been linked to COVID-19 deaths, cardiovascular diseases and neurodegenerative diseases such as Alzheimer’s.

Emily Fischer, an atmospheric science professor at Colorado State University, said those health risks exist even if you can’t smell the smoke.

“Wildfire smoke, once it’s more than a day old, the compounds that you smell are gone,” she said. “So your nose is no longer a good tool for assessing whether we are being impacted by smoke here in the Front Range.”

That’s why Fischer says everyone should check the air quality index, or AQI, before going outside, just like they would check the weather.

“We have two pollutants of concern here that you can check data daily: ozone and fine particulate matter,” she said. “I make decisions for my family living on the Front Range, especially my kids, their outdoor activities, based on that data.”

Air Quality Index (AQI) values and their meanings.
U.S. Environmental Protection Agency
Air Quality Index (AQI) values and their meanings.

For Fischer, an AQI in the orange to light red region means no afternoon exercise and limited outside time for her children. When both ozone and particulate matter levels are high, she said she’s even more conservative.

“That’s a lot to be breathing in,” said Fischer. “And we just don’t understand the health effects of mixtures very well.”

Measuring air quality is expensive, difficult for small communities

Obtaining a precise AQI measurement can be hard to do in smaller communities. Ben Crawford, an environmental science professor at the University of Colorado Denver, said Colorado determines AQI with specific regulatory stations.

“They look like trailers, and they’re full of instruments to measure air pollution,” he said. “Each one of these instruments can cost tens of thousands of dollars, and each one of these trailers to measure a whole bunch of different air pollution measurements can cost hundreds of thousands of dollars.”

That’s why there aren’t many in the state. The stations that do exist only cover areas with long-term pollution issues, like cities.

“But when we have these big events like a wildfire, we suddenly can have air pollution and poor air quality in areas where normally things are pretty good,” said Crawford.

Without nearby expensive regulatory stations, small communities need to find other ways to determine the AQI. Otherwise, residents won’t have the necessary information to make decisions about their own health.

To address that need, Crawford and his team created a low-cost sensor network to monitor air pollution. While cheaper, the sensors are also less accurate. They also need to be calibrated to work correctly. The scientists tested them on the air pollution from a volcanic eruption in Hawaii.

“These low-cost sensors, they work,” Crawford said. “And they can be part of a solution to monitor air quality, especially during these kinds of extreme events.”

Because of its location in the middle of the ocean, Hawaii was an almost pristine test environment. Crawford said they’ll need to adapt the sensors for ozone and wildfire smoke.

“Here in Colorado, in the mountains, it’s going to be more complex,” he said. “It’s more chemically complex, it’s more meteorologically complex, and fire behavior can be much more complex as well.”

As ozone levels remain high and wildfires grow in intensity, measuring and predicting air quality inside and outside of cities will become even more important. Crawford said the more tools we can develop now to help people make healthy decisions, the better.

I am the 2021 American Association for the Advancement of Science Mass Media Fellow at KUNC. My goal is to tell the true stories of science — and make them understandable and fascinating for all.
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