Air pollution is a very serious threat to human health. Each year, hundreds of thousands of premature deaths are linked to this global problem. Various illnesses result as well. Another problem, but one that typically receives less attention, is cognitive decline. A number of research studies have come out in recent years documenting this link. It’s very obvious, if not extremely so, that intelligence is central to human functioning at all levels of human societies.
Without it, we wouldn’t last long. So, when we also begin to figure out that not only does air pollution cause a vast amount of damage to our physical well-being, it also harms our mental capacity, this very deleterious impact should be taken quite seriously.
NYU Assistant Professor of Economics Michael Gilraine studied what happened when a number of schools in the Los Angeles area had air filters installed as a safety measure after a very large natural gas leak occurred. The 2015 Aliso Canyon gas leak had many parents and school administrators concerned about how the potential exposure might impact children in schools. A number of schools had air filters installed to prevent this exposure. Gilraine’s research uncovered an unexpected benefit, however. He answered some questions about his research for CleanTechnica.
How many schools received the air filters?
A. A total of 18.
What kind of air filters were used and how much did they cost?
A. Costs were around $700 per filter and it seems 1,756 filters were delivered. I spent a decent amount of time trying to get the exact plug-in air filter they used. Unfortunately, SoCalGas was the entity that purchased the air filters and so LAUSD had no documentation on it and SoCalGas was unwilling to share due to the ongoing litigation. I also emailed several principals, who confirmed they received the filters, but were unsure on the exact model (one said they had the filters still in storage, so if I flew out to LA I could likely figure it out…).
I can definitely tell you that the plug-in air purifiers came from the following list of filters that the California Air Resource Board approved for the leak. Indeed, according to a press release from BlueAir, SoCalGas purchased 210 of the Blue Air filters on that list in early January 2015, making me think that they likely put those filters in the schools (in fact, that number is the exact same as the number of air filters delivered to Granada Hills High School) but I cannot confirm that is the exact model used as SoCalGas could have ordered filters from multiple companies. The key (according to an someone who knows air filters who I talked to) is that they appeared to have purchased filters with a reasonably deep carbon layer in addition to its HEPA particle filter.
How old were the students in those schools at the time?
What, in a lay person’s view, does this figure mean.. can it be converted to a percentage increase?
“…air filter exposure led to a 0.20 standard deviation increase in mathematics and English scores.”
A. The 0.20 standard deviation test score increase is around the same found in a (quite well-known) RCT run in the late-1980s called Project STAR that reduced class sizes from (around) 22 to 15 students.
How did you establish a correlation between air filter installation and increased academic scores?
A. Since air filters were just installed in schools within five miles of the gas leak, the basic idea is to compare test score growth in the year the air filters were installed for schools just within five miles of the leak (and thus receive air filters) and those just outside (who do not).
Were the air filters installed in individual classrooms or at the level of the central HVAC system?
What pollutants were removed from the schools’ indoor air?
A. A bit unclear as I do not have detailed pollution measures within the schools (they did test the air within schools, but this testing mostly focused on methane). These air filters are supposed to eliminate particulate pollution (e.g. dust, pollen) and VOCs (e.g. methane).
Was any gas from the leaks detected in the schools?
A. There is no strong evidence of abnormally high methane levels according to air quality testing done in the schools. The LAUSD did evacuate two schools very near the leak (<2 miles), however, and these schools did seem to have relatively high methane levels (these students were relocated to schools about 7 miles from the leak). These schools were not included in the analysis (indeed, they did not receive filters).
Were any measurements taken related to physical health, like noting a reduction in respiratory illness or asthma, as well?
Do you think schools with polluted indoor air are potentially experiencing student cognitive issues due to the exposure?