Study: Western wildfires bring 'new peak to air pollution'

The large, intense wildfires that have scorched the Pacific Northwest in recent years are altering the seasonal pattern of air pollution and causing a surge in unhealthy air pollutants in August -- as well as undermining clean air gains and posing potential health risks to millions across the continent, a new study found.

The research, helmed by scientists at the National Center for Atmospheric Research and published this week in Nature Communications, pointed to a sharp increase in carbon monoxide levels during the month of August -- a time when carbon monoxide levels have historically remained low.

While this gas generally is not a significant health concern outdoors, it indicates the presence of more harmful pollutants like aerosols and ground-level ozone.

Normally, carbon monoxide levels in the summer have remained low due to chemical reactions in the atmosphere related to sunlight, the press release on the study said.

The discovery that these levels have instead jumped during the summer as Western wildfires spread underscores the extent of the smoke's impact.

"Wildfire emissions have increased so substantially that they're changing the annual pattern of air quality across North America," said NCAR scientist Rebecca Buchholz, the lead author of the study. "It's quite clear that there is a new peak of air pollution in August that didn't used to exist."

The findings were particularly striking since carbon monoxide levels have otherwise been decreasing -- globally and across North America -- due to improvements in pollution-control technologies, she added.

Findings from the Intergovernmental Panel on Climate Change further underscored the outcome of the study.

"The IPCC reports on climate change show that fire seasons have lengthened by nearly 20 globally since the 1980s and that wildfires could happen 30 more frequently by 2050," Plume Labs Founder Romain Lacombe told AccuWeather, which acquired Plume Labs earlier this year.

"Wildfires are estimated to release 2.2 gigatons of carbon in the air annually," Lacombe said.

In 2016, researchers at Climate Central noted that the annual average wildfire season in the western U.S. was 105 days longer than it was in the 1970s, burned six times as many acres and had three times as many large fires -- those burning over 1,000 acres.

The research team behind the new report used satellite-based observations of atmospheric chemistry and global inventories of fires to track wildfire emissions from 2002 to 2018 alongside computer modeling to analyze the potential impacts of the smoke, focusing on three regions: the Pacific Northwest, the central U.S. and the Northeast.

Not only did they find the increase in carbon monoxide levels across North America during the month of August, but they found that the trend became more pronounced from 2012 to 2018, when the Pacific Northwest fire season became more active, a press release on the study said.

This year's wildfire season is expected to be another active one, with the number of fires and acreage burned already running well above the 10-year average to date, according to AccuWeather Meteorologist Brandon Buckingham.

AccuWeather is expecting an above-normal wildfire season in 2022, with early predictions of 67,000-70,000 fires.

The average number of fires from the 2001-2020 seasons is 68,707 fires.

"The aridification of the West as a result of a multi-decadal drought and climate change will only continue to heighten the wildfire threat in 2022 and years to come," Buckingham said.

"Studies have now revealed that the ongoing drought across the West is the worst that the region has experienced since 800 A.D., found by extensive study via tree ring analysis across the West," Buckingham said.

Human-caused climate change has been responsible for over half of the increase in fuel aridity in the western U.S. since the 1970s, according to a study published by the peer-reviewed journal Proceedings of the National Academy of Sciences of the United States of America, doubling the cumulative area burned in forest fires since 1984.

This season, below-average precipitation east of the Cascades in Washington and across a majority of Oregon during the winter season has further dried out the area's foliage and is expected to lead to a higher-than-average risk for wildfires this season, according to Buckingham.

While the risk of a thunderstorm complex or two during late June to July across the Pacific Northwest could bring bouts of rainfall, it could also bring a higher risk of lightning strikes, which can lead to complex fires. The higher risk for this resides in Oregon, Buckingham said.

The researchers were able to attribute the Western wildfires to the far-reaching spike in air pollutants in August by first ruling out the possibility of it originating from pollution carried overseas, from other regional fire seasons and fossil fuel emissions. Upwind of the Pacific Northwest in the Pacific Ocean, measured carbon monoxide levels were lower in August, ruling out transference from Asia.

As for the other two variables, fire seasons in the Central states and Northeast didn't coincide with the August increase, and the pair of fossil fuel emission inventories that showed emissions from human activities didn't increase in any of the three regions from 2012 to 2018.

"Multiple lines of evidence point to the worsening wildfires in the Pacific Northwest as the cause of degraded air quality," Buchholz said. "It's particularly unfortunate that these fires are undermining the gains that society has made in reducing pollution overall."

Air pollution from wildfire smoke differs from "normal" air pollution generated by human activity, according to Plume Labs.

For one thing, pollution from wildfires is more intense, meaning that a large amount of particulate matter, or PMs, and gases are released within a relatively short period of time. It also carries more volatile organic compounds, or VOCs.

And these hazards are capable of remaining active over long periods of time in the atmosphere as they travel.

Findings from Plume Labs Chief Atmospheric Scientist Dr. Boris Quennehen on the composition of anthropogenic -- man-made -- and forest fire pollution transported from mid-latitudes to the Arctic showed that processes affecting particle size and concentration remain active after several days of traveling in the atmosphere.

Usually, as the smoke moves away from the fire, it's lofted into the higher altitudes of the atmosphere.

There have been plenty of hazy orange sunsets in the Northeast prompted by Western wildfires, but the pollutants at higher altitudes aren't necessarily immediately harmful, as the pollution isn't being breathed in by people at ground level.

In 2021, however, a high pressure pushed the transported smoke in the Northeast down toward the surface, prompting air quality warnings across the region.

While wildfire air pollution doesn't carry the same level of toxic gases due to plastic or mineral oil burning as anthropogenic air pollution, it still poses a threat to a population's health due to the sheer amount of particulates released -- and the NCAR study estimates that the pollutants from the Pacific Northwest wildfires could impact more than 130 million people.

That includes about 34 million people in the Pacific Northwest, 23 million in the central U.S. and 72 million in the Northeast.

The study didn't specifically investigate the health implications of the emissions, but the authors did look at respiratory death rates in Colorado -- where state respiratory death rates were readily available -- and compared the month of August from 2002 to 2011 with August of 2012 to 2018.

They found respiratory deaths during that month in the state increased significantly during the 2012-2018 time frame -- a period during which fires in the Pacific Northwest, but not Colorado, produced more emissions in August.

"It's clear that more research is needed into the health implications of all this smoke," Buchholz said. "We may already be seeing the consequences of these fires on the health of residents who live hundreds or even thousands of miles downwind."

The most common health risks associated with smoke exposure are found within the lungs, Dr. Jonathan Tan from the Philadelphia Children's Hospital told Plume Labs in a 2019 interview.

"In my experience working in hospitals around the world, smoke exposure also increases in the use of emergency department, hospitalizations and need for medications during wildfire disasters," Tan said.

"This has an impact across almost all aspects of patient care," Tan said.

Some populations are also more affected by smoke exposure, and health effects may be exacerbated for someone with a heart or lung or pulmonary disease.

Older adults, pregnant people, children, smokers and people involved in strenuous outdoor work or outdoor sports may also be more affected by smoke exposure.

"With the health of millions of people at stake, the air pollution impact of these more frequent fires is yet another reason we need strong and urgent action on climate," Lacombe said.