Wildfires are increasing dramatically in size and frequency around the world.1,2 Extreme wildfires emit vast volumes of pollutants, including fine particulate matter (),3 which is associated with effects on cognitive functioning4,5 and other significant health risks.6 During periods of wildfires, air quality is further worsened by harmful gases and organics whose combined impact is not necessarily the same as ambient in other scenarios.7 New research in Environmental Health Perspectives examined both ambient and wildfire-related in the United States in relation to cognitive functioning.8
In the new study, was associated with reduced attention in adults within hours of exposure, an association that was especially pronounced among residents of western states, which are particularly burdened by wildfires. The findings suggest that “neurological impacts from air pollution are a special concern to communities in wildfire-impacted regions because of their recurring exposures to smoke,” says first author Stephanie Cleland, a PhD candidate in environmental sciences and engineering at the University of North Carolina at Chapel Hill. Cleland is also an Oak Ridge Institute for Science and Education research fellow at the U.S. Environmental Protection Agency (EPA).
To assess how wildfire-related might affect people’s ability to focus, the investigators turned to a unique digital resource: the scores racked up by players of an online game called Lost in Migration,9 which was designed to help people measure and improve their attention span.10 Players are shown pictures of five birds oriented in various directions, then must determine if the middle bird is pointing left, right, up, or down. New flocks appear in rapid succession, and players are scored based on their speed and accuracy.
The investigators had access to scores from a cohort of 10,228 players aged 18 years and older in the contiguous United States. Among these were 1,809 players who lived in the western states of Oregon, Washington, California, Montana, Idaho, and Nevada. The researchers limited their analysis to the first 20 games each individual had ever played. The game’s developer, Lumos Labs, also provided anonymized data, including the first three digits of each player’s zip code (ZIP3) at the time they created a game account, as well their age, sex, and education level.
The authors used ground-based monitoring data from the EPA’s Air Quality System database and the PurpleAir network to estimate ambient exposures for each ZIP3 location. Wildfire smoke exposures for western populations were estimated using satellite data gathered by the National Oceanic and Atmospheric Administration. Whereas the EPA and PurpleAir’s data are available in hour and minute intervals, respectively, wildfire smoke data are available on a daily basis only. The satellite observations of smoke were classified by density based on estimated concentration of wildfire-related : light (), medium (), or heavy (). The researchers then calculated the maximum daily density in each ZIP3 to denote smoke exposure.
The analysis showed an association between short-term exposures to and poorer cognitive performance. For example, every increase in maximum hourly ambient 3 hours prior to gameplay was associated with an average drop in scores of 21 points for all contiguous U.S. users and 42 points for just western users. Similarly, heavy wildfire smoke density on the day prior to gameplay was associated with an average 117-point drop in scores. Among western players, same-day exposure was associated with an overall average 887 fewer points over 20 plays (roughly 18 fewer correct answers). Players overall averaged 529 fewer points over 20 plays (approximately 11 fewer correct answers). The associations with poorer performance were more pronounced among males and among players aged either or 70 and older.
Senior author Ana Rappold, who is Clinical Research Branch Chief in the EPA’s Public Health and Integrated Toxicology Division, says residents affected by wildfire smoke often complain of “foggy brain,” difficulty concentrating, and other cognitive problems that epidemiological studies of air pollution typically do not address. Findings from the study, she says, suggest that smoke exposures trigger these effects within hours. However, she adds, wildfires are very stressful events, and it is impossible to decouple any effects of stress from the effects of exposure in an observational study.
Laura McGuinn, an environmental epidemiologist at the Icahn School of Medicine at Mount Sinai in New York, who was not involved in the research, applauds the study. “There’s quite a bit of temporal variation in particulate matter during the day, during which some populations might experience critical windows of vulnerability,” she says. “So subdaily exposure estimates from this research add a lot of innovation to the field.”
Still, pollutant levels—and therefore individual exposures—can also vary widely within the spatial areas denoted by ZIP3 codes, McGuinn points out. The fact that the researchers were unable to account for exposure variations within ZIP3 locations, she says, is a limitation of the study.
Marc Weisskopf, a professor of environmental epidemiology and director of the Harvard Chan–National Institute of Environmental Health Sciences Center for Environmental Health, adds that ZIP3 sign-up locations for some people might also have differed from where they actually played the game. For instance, someone might have signed up in Colorado and then moved to Texas, says Weisskopf, who also was not involved in the research. Better accounting of individual exposures in specific locations, he says, would likely only have strengthened the associations detected in the study. Meanwhile, he says, access to large-scale data sets emerging from online games such as Lost in Migration “leads to incredibly intriguing opportunities for environmental health studies of the brain.”
Charles W. Schmidt, MS, is an award-winning journalist in Portland, Maine, whose work has also appeared in Scientific American, Nature, Science, Discover Magazine, Undark, the Washington Post, and many other publications.
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