Clearing the air in class may help students think more clearly, too, according to a New York University study.
Los Angeles schools that installed air filters in every classroom and common area following a nearby gas leak saw significant boosts to reading and math achievement—even though the outdoor pollution didn’t prove to be a problem.
The findings suggest improving air quality may also help bolster school improvement efforts for disadvantaged students who often live in more polluted areas and attend class in older buildings.
In fact, “given the large test-score increases they generate, installing air filters substantially outperforms other education reforms such as class-size reduction on a cost-benefit basis,” said Michael Gilraine, study author and assistant professor of economics at New York University.
Schools are not required to track their indoor air quality, but the Environmental Protection Agency estimates nearly half of campus buildings contain unhealthy levels of dust, mold, chemicals, carpet fibers, and other pollutants. Moreover, efforts to make older buildings more energy efficient can lead to build-up of carbon dioxide if outside air does not circulate regularly.
“You can actually have pretty good indoor air quality and pretty poor outdoor air quality or vice versa,” Gilraine said.
Gilraine used the 2015 Aliso Canyon gas leak, the largest in U.S. history, to explore the effects of air quality on students’ math and reading scores. Over a period of nearly four months, the Southern California Gas Company struggled to contain an inadvertent leak that emitted methane gas and other chemicals into a wealthy Los Angeles neighborhood. The amount released was estimated to equal the yearly emissions of 572,000 cars.
Two schools within two miles of the factory tested as having high levels of methane; they were evacuated and students were relocated to other campuses. But the company also installed significant air quality improvements at 18 other elementary schools located 3 ½ to five miles from the leak—a distance chosen somewhat randomly, based on the furthest distance from which the company had received gas odor complaints. These air improvements included more than 1,700 plug-in air filters, in every classroom, office, and common area, and active-carbon filters in every heating and air conditioning system in each of the schools.
Schools’ air quality was tested repeatedly before and after the filters were installed. It focused on both methane and volatile organic compounds like benzene, toluene, and xylene. Gilraine analyzed both the air quality and the math and reading test scores for students at the 18 schools, as well as a control group of elementary schools just outside the filter zone. Overall, none of the schools showed much contamination from the gas leak; in fact, the outside pollutant concentration in that part of Los Angeles during the four months of the leak was 9.1 grams of fine particles per cubic meter, lower than the average fine-particle concentration of 9.5 in New York City, 9.6 in Chicago, or 10.6 in Houston during the same time, based on EPA sensors. “Fine particles"—defined as having diameters of 2.5 micrometers or less, or about 20 times smaller than the diameter of a human hair—have been shown to penetrate and lodge deep in the tiny air sacs of the lungs, and have been linked to both respiratory damage and concentration problems.
But while little outside air pollution seemed to make it into the schools, the filters did seem to make a difference clearing schools’ indoor contaminants, Gilraine found.
After installing the filters, the indoor volatile compound levels dropped 60 percent to 100 percent in schools. And by the end of the 2015-16 school year, in schools that received the new air filters, students improved by .18 of a standard deviation in reading and .2 of a standard deviation in math, compared to students’ performance in the schools that did not receive air filters. To put that in perspective, those gains are about equal to the learning benefits from reducing class sizes or providing intensive tutoring. Students sustained those math and reading gains the next year, particularly if they attended the same school or another that had installed new filters in the following year.
Prior studies have found that better air quality can lead to fewer teacher and student absences, particularly for those with chronic asthma or other respiratory illnesses. While schools with the new air filters installed did have lower student absenteeism, Gilraine said attendance alone didn’t seem to be driving the gains in math and reading achievement.
Rather, he said, “you can get a lot just from being able to think clearly while you take a test. And then you also might be learning a bit better because you’re thinking clearer” in class from day to day, he said.
Separate longitudinal studies have found rising average temperatures likewise can increase indoor air pollution and reduce student achievement, particularly if students take tests on hot days. But the current study, which tracked air filter use over four months, found benefits two to five times larger than the benefits found for air quality improvements limited to a specific day when students took a test.
Gilraine estimated the air quality improvements cost about $1,000 annually per classroom, including installation, electricity, and regularly replacing filters.
Those cost benefits could be even greater in high-poverty areas, where students often live in older homes and neighborhoods with higher pollution, and attend school in older buildings. The Los Angeles study suggests that school and district leaders should start to think about improving their school climate more literally, he said.
“We’ve had a decade or more of research into the effects of lead. There’s been much less research on the effects of air quality, especially on cognition. ... We’re still in early days,” he said. “I think the main takeaway here is, indoor air pollution is a natural place to start focusing more attention, because most of students’ day is spent indoors.”
A version of this article appeared in the February 12, 2020 edition of Education Week as Air Filters: a Possible New Tool to Boost Learning