The Health Effects of Hazy Air


Thanks to wildfires popping up all over the Northwest US (and Canada), Montanans have been dealing with a recent spate of smoky air. Here in Bozeman, we had days in which the peak Air Quality Index (AQI) exceeded 100 (signifying “unhealthy for sensitive groups”) for roughly a week straight, an unusually bad stretch for the area. Air quality fluctuates widely from year to year and even week to week, but as wildfire frequency is likely to continue to increase due to climate change, we can expect occasional stretches of bad air to become more commonplace as well. Back in 2017 I wrote a post about research on the health impacts of wildfires and poor air quality. But there have been several interesting studies on this topic since, so I thought now would be a good time for an update.

A number of papers have documented the effects of poor air quality on cognitive function. Past studies have shown that air pollution negatively impacts children’s test scores, but less work has been done for adults, who don’t typically take standardized tests. But a couple of recent papers have overcome this limitation in clever ways. A 2018 study (link) analyzes how the performance of Major League Baseball umpires is affected by air quality. MLB umpires work in a unique setting, where every decision they make regarding balls and strikes can be objectively evaluated with technology that determines whether the ball passed through the strike zone. Umpiring accurately over the course of a game takes a high level of concentration and skill, so if air pollution does impact cognitive ability in real time it should be detectable in umpire performance. The paper does find that higher pollution results in more incorrect calls, though the effect is arguably small. The paper states that “a 3% reduction in productive output is associated with a change in CO concentrations equivalent to moving from the 25th to the 95th percentile of the CO distribution in many of the largest US cities.”

Another study (link) uses a similar methodology to evaluate speech patterns from politicians. It uses standardized textual analysis that evaluates the quality and complexity of speech from nearly 120,000 speeches made in the Canadian House of Commons from 2006-2011. The authors find that exposure to elevated levels of PM2.5 (particulate matter that is 2.5 micrometers in diameter or smaller) causes an average 2.3% reduction in speech quality—again a modest but meaningful effect.

So it might be good to note that on smoky days you might be a touch less sharp than usual, but there are more serious long-term cognitive concerns as well. A working paper finds that higher average PM2.5 concentrations is associated with increased probability of a dementia diagnosis. Fortunately for Montanans, even with the wildfire smoke our average air quality is much better than for the vast majority of Americans who live in areas with higher population density, so these kinds of cumulative long-run health effects will be less severe.

But for long-term health effects in general, the more we study air pollution, the worse it gets. A summary of this research was presented to Congress last year by Drew Shindell of Duke University. Air pollution already causes an alarming 250,000 premature deaths in the US every year, along with all kinds of non-mortal but still serious health effects. By this analysis, making the significant investments needed to decarbonize the economy would be a net benefit for the health benefits of reduced air pollution alone. In other words, it would be worth it even if climate change did not exist.


About Author

Brock Smith is an Assistant Professor in the Department of Agricultural Economics and Economics at Montana State University. He received a PhD from UC-Davis in 2013 and spent three years as a Research Fellow at the Oxford Centre for Analysis of Resource Rich Economies. He mainly studies effects of oil and natural gas shocks in both an international and domestic US setting.

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