Air Pollution Reduces IQ, a Lot

The number and quality of studies showing that air pollution has very substantial effects on health continues to increase. Patrick Collison reviews some of the most recent studies on air pollution and cognition. I’m going to post the whole thing so everything that follows is Patrick’s.


Air pollution is a very big deal. Its adverse effects on numerous health outcomes and general mortality are widely documented. However, our understanding of its cognitive costs is more recent and those costs are almost certainly still significantly under-emphasized. For example, cognitive effects are not mentioned in most EPA materials.

World Bank data indicate that 3.7 billion people, about half the world’s population, are exposed to more than 50 µg/m³ of PM2.5 on an annual basis, 5x the unit of measure for most of the findings below.

  • Substantial declines in short-term cognitive performance after short-term exposure to moderate (median 27.0 µg/m³) PM2.5 pollution: “The results from the MMSE test showed a statistically robust decline in cognitive function after exposure to both the candle burning and outdoor commuting compared to ambient indoor conditions. The similarity in the results between the two experiments suggests that PM exposure is the cause of the short-term cognitive decline observed in both.” […] “The mean average [test scores] for pre and post exposure to the candle burning were 48 ± 16 and 40 ± 17, respectively.” – Shehab & Pope 2019.
  • Chess players make more mistakes on polluted days: “We find that an increase of 10 µg/m³ raises the probability of making an error by 1.5 percentage points, and increases the magnitude of the errors by 9.4%. The impact of pollution is exacerbated by time pressure. When players approach the time control of games, an increase of 10 µg/m³, corresponding to about one standard deviation, increases the probability of making a meaningful error by 3.2 percentage points, and errors being 17.3% larger.” – Künn et al 2019.
  • A 3.26x (albeit with very wide CI) increase in Alzheimer’s incidence for each 10 µg/m³ increase in long-term PM2.5 exposure? “Short- and long-term PM2.5 exposure was associated with increased risks of stroke (short-term odds ratio 1.01 [per µg/m³ increase in PM2.5 concentrations], 95% CI 1.01-1.02; long-term 1.14, 95% CI 1.08-1.21) and mortality (short-term 1.02, 95% CI 1.01-1.04; long-term 1.15, 95% CI 1.07-1.24) of stroke. Long-term PM2.5 exposure was associated with increased risks of dementia (1.16, 95% CI 1.07-1.26), Alzheimer’s disease (3.26, 95% 0.84-12.74), ASD (1.68, 95% CI 1.20-2.34), and Parkinson’s disease (1.34, 95% CI 1.04-1.73).” – Fu et al 2019. Similar effects are seen in Bishop et al 2018: “We find that a 1 µg/m³ increase in decadal PM2.5 increases the probability of a dementia diagnosis by 1.68 percentage points.”
  • A study of 20,000 elderly women concluded that “the effect of a 10 µg/m³ increment in long-term [PM2.5 and PM10] exposure is cognitively equivalent to aging by approximately 2 years”. – Weuve et al 2013.
  • “Utilizing variations in transitory and cumulative air pollution exposures for the same individuals over time in China, we provide evidence that polluted air may impede cognitive ability as people become older, especially for less educated men. Cutting annual mean concentration of particulate matter smaller than 10 µm (PM10) in China to the Environmental Protection Agency’s standard (50 µg/m³) would move people from the median to the 63rd percentile (verbal test scores) and the 58th percentile (math test scores), respectively.” – Zhang et al 2018.
  • “Exposure to CO2 and VOCs at levels found in conventional office buildings was associated with lower cognitive scores than those associated with levels of these compounds found in a Green building.” – Allen et al 2016. The effect seems to kick in at around 1,000 ppm of CO2.

Alex again. Here’s one more. Heissel et al. (2019):

“We compare within-student achievement for students transitioning between schools near highways, where one school has had greater levels of pollution because it is downwind of a highway. Students who move from an elementary/middle school that feeds into a “downwind” middle/high school in the same zip code experience decreases in test scores, more behavioral incidents, and more absences, relative to when they transition to an upwind school”

Relatively poor countries with extensive air pollution–such as India–are not simply choosing to trade higher GDP for worse health; air pollution is so bad that countries with even moderate air pollution are getting lower GDP and worse heath.

Addendum: Patrick has added a few more.


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