Vog from Hawaii’s volcanoes might be hurting students’ ability to think and reason, as indicated by lower test scores, according to a new study by researchers from the University of Hawaii and University College London.

The study of Hawaii public school student performance from 2015 to 2018 found that poor air quality due to vog, or volcanic smog, from the volcano Kilauea on Hawaii island correlated with a small but “statistically significant” decline in average test scores.

And those students who were economically disadvantaged, and those living in areas with a higher baseline level of particulates in the air over time, such as south Hawaii island, saw test scores drop the most, the study found.

A key takeaway is that “the pollution affects the amount that is learned by poorer kids by a much larger factor than for better-off kids. And we show that the effects for these kids are pretty enormous,” said UH economics professor Timothy Halliday, part of the team of researchers from the UH Manoa Department of Economics, the UH Economic Research Organization and University College London.

“So basically, the pollution is effectively exacerbating preexisting (socioeconomic) inequalities by a pretty large margin,” Halliday said.

Vog — a mixture of ash, plus sulfur dioxide and other gases — is popularly known mainly as a trigger for physical problems, such as breathing difficulties, headaches, sore throat, and watery or itchy eyes.

But a small but growing body of research is pointing also to detrimental effects of air pollution on cognition. A 2020 study found links between traffic pollution on student test scores and other shorter-term outcomes in Florida, for instance, and a 2021 study showed higher concen­trations of particulates in the air resulted in lower scores on college entry examinations in Brazil.

The biological processes in which air pollution may affect the brain are not well understood, Halliday said, but theories include that pollution triggers inflammation responses in the body.

The Hawaii study looked at test scores from 2015 to 2018 on the Smarter Balanced Assessment, a mandatory test of math and English literacy skills that is given by the state Department of Education to students in grades 3 through 8 and grade 11.

Data from more than 150,000 students across 260 schools was examined. Half the students in the sample were considered economically disadvantaged, and roughly 6% received English language services.

The Hawaii study also charted levels of two pollutants, particulate matter and sulfur dioxide, from air quality data from the state Department of Health.

Vog across the state has been a frequent effect of eruptions at Kilauea, including the 35-year eruption at the cinder-and-spatter cone Pu‘u‘o‘o, and a dramatic new eruption of Kilauea in 2018. Concerns about vog have been renewed also with this year’s eruption of nearby Mauna Loa.

The study authors looked at particulates classified as “PM2.5,” which are fine inhalable particles with diameters that are generally 2.5 micrometers and smaller, and sulfur dioxide, a toxic gas produced by volcanic activity. Using wind variation and pollution measurements from Health Department monitoring stations, the authors predicted levels of air pollution at a given school.

The researchers found that students at schools with an average of 9 micrograms per cubic meter of PM2.5 or higher had roughly seven times the decline in test scores of those with less than 9 micrograms per cubic meter of PM2.5.

Therefore, there was a 1% decline in test scores for every standard deviation increase of 1.84 micrograms per cubic meter in PM2.5. The effect was worse in areas with more air pollution.

The study also found that the effects of poor air quality fell more heavily on poor pupils, defined as those who qualify for federal programs such as free and reduced-price lunch. The effects of PM2.5 were larger by a factor of 10, and the effects of sulfur dioxide were larger by a factor of six. This was true among students within the same schools.

“This finding has great implications for environmental justice,” Rachel Inafuku, a researcher at the UH Economic Research Organization and co-lead author of the study, wrote in a blog. “Students who are more financially stable face less obstacles in accumulating human capital when air quality is poor, suggesting that pollution contributes to the inequality gaps that we observe here in Hawaii and in the U.S.”

Halliday said he hopes the study will spur the state to study school air quality more closely, and to look at steps to raise public awareness of vog levels so that people can choose whether to take protective measures. He said he expects the study will spur parents who live in areas with frequent vog, or who have children who are sensitive to pollutants, to consider air conditioning or air filtration.

Tammi Chun, a deputy superintendent at the Hawaii DOE, said the study “addresses a complex issue” and noted that it is still under peer review.

“Our public schools take precautionary measures to ensure a safe school environment when there are vog conditions,” Chun added. “For more than a decade, Hawaii Island schools have been utilizing sulfur dioxide monitors to monitor vog conditions, and school staff are trained on how to respond to elevated levels in classrooms.”

During the 2018 Kilauea event, the DOE worked with Big Island schools to distribute air purifiers and to establish at all schools “safe rooms,” or designated areas on campus with proper filtration if sulfur dioxide levels reach elevated threshold, Chun said. Similar precautions were in place during the recent Mauna Loa eruption.