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308 points tangjurine | 3 comments | | HN request time: 0.711s | source
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Aurornis ◴[] No.43529859[source]
I'm all for installing air filters in classrooms for a number of reasons, but I also think the extreme results from this study aren't going to hold up to further research.

From the paper:

> To do so, I leverage a unique setting arising from the largest gas leak in United States history, whereby the offending gas company installed air filters in every classroom, office and common area for all schools within five miles of the leak (but not beyond). This variation allows me to compare student achievement in schools receiving air filters relative to those that did not using a spatial regression discontinuity design.

In other words, the paper looked at test scores at different schools in different areas on different years and assumed that the only change was the air filters. Anyone who has worked with school kids knows that the variations between classes from year to year can be extreme, as can differences produced by different teachers or even school policies.

Again, I think air filtration is great indoors, but expecting test scores to improve dramatically like this is not realistic. This feels like another extremely exaggerated health claim, like past claims made about fish oil supplements. Fish oil was briefly thought to have extreme positive health benefits from a number of very small studies like this, but as sample sizes became larger and studies became higher quality, most of the beneficial effects disappeared.

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1. evil-olive ◴[] No.43530415[source]
> but I also think the extreme results from this study aren't going to hold up to further research.

there already is further research. and the results do seem to be holding up.

the study you're quoting from is the one linked in the 2nd paragraph of the article. this is from the 3rd paragraph:

> But it’s consistent with a growing literature on the cognitive impact of air pollution, which finds that everyone from chess players to baseball umpires to workers in a pear-packing factory suffer deteriorations in performance when the air is more polluted.

that paragraph links to an earlier Vox article [0] which goes into more detail, and well as linking to all of the various studies:

> A wide range of studies about the impact of pollution on cognitive functioning have been published in recent years, showing impacts across a strikingly wide range of endeavors. Stripe CEO Patrick Collison has taken an interest in this subject and compiled much of the key research on his personal blog. Among the findings he’s highlighted include:

> - Exposure to fine particulates over the long term leads to increased incidences of dementia and Alzheimer’s disease in the elderly (a second study confirms this).

> - A study of 20,000 older women found that 10 micrograms of additional long-term particulate exposure is equivalent, across the board, to about two additional years of aging.

> - The impacts are not limited to the elderly, however, nor are they exclusively long-term. A range of specialized professionals also seem to suffer short-term impairment due to air pollution. Skilled chess players, for example, make more mistakes on more polluted days. Baseball umpires are also more likely to make erroneous calls on days with poor air quality. Politicians’ statements become less verbally complex on high-pollution days, too.

> - Ordinary office workers also exhibit these impacts, showing higher scores on cognitive tests when working in low-pollution ( or “green”) office environments. Individual stock traders become less productive on high-pollution days.

> - The same also appears to be true for blue collar work. A study of a pear-packing factory found that higher levels of outdoor particulate pollution “leads to a statistically and economically significant decrease in packing speeds inside the factory, with effects arising at levels well below current air quality standards.”

> - Last but by no means least, the cognitive impacts appear to be present in children, with a Georgia study that looked at retrofits of school buses showing large increases in English test scores and smaller ones in math driven by reduced exposure to diesel emissions.

0: https://www.vox.com/future-perfect/2019/12/11/20996968/air-p...

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2. Aurornis ◴[] No.43531074[source]
> there already is further research. and the results do seem to be holding up.

You’re conflating different results.

The results of the headline study are dramatic in ways that aren’t holding up. The test score increase happened after a single year of putting air filters in class rooms. That’s minimal exposure to purified air for a fraction of the day, 5 days a week, for less than a year of classes.

The other studies are much longe term and look at things like decades of exposure at city scale.

Do you see the difference? The study tried to claim that purifying air immediately improved test scores by dramatic amounts.

There are other serious limitations in the study, like the fact that they can’t even identify which air purifiers were installed or how effective they were. There’s a footnote that says many weren’t even used. There’s a section on air quality monitoring that says they didn’t even detect the VOCs they were trying to filter before they started filtering.

This is the type of study that people implicitly believe because it makes logical sense, but when you read the details you realize that there isn’t much substance in it.

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3. fc417fc802 ◴[] No.43533312[source]
> The other studies are much longe term and look at things like decades of exposure at city scale.

Are they? Several towards the end of the list are specifically about short term day-to-day effects across a range of situations.

> There’s a footnote that says many weren’t even used.

Quite damning if true.

> they didn’t even detect the VOCs they were trying to filter before they started filtering

That is confusing the reasoning that led to the company footing the bill versus what was being looked at here. The lack of VOCs is actually in the author's favor as it eliminates "exposure to atypical VOCs" as an otherwise fairly severe confounding factor.