Smoke from distant wildfires in 2015 may have led to an increase in asthma-related doctor visits in Colorado, recent research shows. This finding could influence how communities are warned about smoke hazards.
Severe wildfires, like the recent Camp fire in Paradise, Calif., have been increasing across the West, devastating nearby communities. New data presented on 13 December at AGU’s Fall Meeting 2018 in Washington, D. C., highlight the impact that even distant wildfire smoke could have on our respiratory health.
“Wildfire smoke is different than what you breathe out on the street,” said Katelyn O’Dell, a graduate student from Colorado State University in Fort Collins who presented the findings. Ambient air pollution from cars and factories has already been linked to a number of health problems, including acute respiratory infections, heart disease, and lung cancer. Some of this pollution is soot that you can see, but air particles that are less than 2.5 micrometers in diameter—think 30 times smaller than the width of a human hair—are especially harmful to our health because they can invade deep into our lungs and cross into our bloodstream. And particles from smoke tend to fall into this category.
Carbon dioxide, water vapor, carbon monoxide, and thousands of other compounds are blended together in smoke, but it remains unclear what the health consequences are. Thus, understanding how wildfire season affects the respiratory system would be valuable.
“Wildfires come through and increase [exposure] dramatically for a couple days,” O’Dell said. “So you can imagine being exposed to a lot of it just for a few days might have a different health impact than being exposed to a mild amount of particles for your whole life.”
O’Dell and her colleagues looked at three different fire seasons: Washington and Colorado in 2012, Oregon in 2013, and Colorado in 2015. The researchers combined air quality measurements, a forecasting model, and satellite data to monitor where smoke most heavily affected air quality in these states during wildfires.
The researchers compared the number of doctor visits related to respiratory problems, inhaler prescription refills, and reported respiratory problems on days when smoke was in the air with these numbers on days without smoke. They found a link between these numbers and the concentration of heavy smoke particulates.
The team found evidence that wildfire smoke increased asthma cases in both Washington and Oregon in 2012 and 2013, respectively. A 10 microgram per cubic meter increase in smoke was associated with a 9.5% increase in the rate of asthma admissions in hospitals and urgent care clinics.
“Ten micrograms per cubic meter [of smoke] is on the edge of whether or not you can see it,” said O’Dell. “Even I have looked outside, and it looks hazy in the summer, and I think ‘oh it’s foggy.’ But then I’ll go look it up because that’s what I do.” According to O’Dell, smoke levels around 20 or 30 micrograms per cubic meter are more visible.
Distant Wildfires, Local Impacts
Colorado served as a special case for O’Dell and her colleagues. Local fires plagued the state in 2012, including one near O’Dell’s department at Colorado State University in Fort Collins. A few years later, they were hit by smoke from distant fires in the Pacific Northwest.
When the team analyzed the risk statistics for respiratory disease in both of these seasons, they found a surprising decrease in asthma risk from local fires. But they still saw an asthma risk increase from far-away fires in 2015, similar to what they’d seen in Washington and Oregon.
“Potentially, people know when there are local fires; ‘I can see the fire and the smoke, so I’m going to stay inside,’” O’Dell said. “Whereas in 2015, smoke is coming from further away, so you might not even notice.”
The reason for this unexpected result is still an active area of research, but the team faces challenges. Fort Collins is mountainous, which makes it difficult for satellites and models to estimate smoke from fires in the area, according to O’Dell. Wildfire smoke from far away, however, is more diffuse and easier to track.
Fiona Lo, an atmospheric science graduate student at the University of Washington in Seattle who was not involved in the study, said that the results are intriguing and have a lot of potential. She noted, however, that more research needs to be done to confirm the findings for them to be convincing.
The next steps for O’Dell involve communicating fire risk to the public. The research team has already set up a beta version of a website that could act as a “daily smoke forecast.” It estimates asthma risk during prescribed burns and wildfires on the basis of the data they have collected so far.
“People should be aware that even if you can’t see the smoke, it can have effects on your health,” said O’Dell. “Not everyone is going to be like me and look up what the concentration is before going on my run.”
Garcia de Jesus, E. I. (2019), Invisible wildfire smoke has visible health impacts, Eos, 100, https://doi.org/10.1029/2019EO113561. Published on 11 January 2019.
Text © 2019. The authors. CC BY-NC-ND 3.0
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