In October, researchers at the University of Aberdeen published an alarming study.
For the first time, they found air pollution particles in the developing lungs and brains of unborn babies, raising concerns about the impact pollution has on a child’s development in the womb.
Warnings about the damaging effects of pollution are nothing new; the study from Aberdeen is the latest in a long line of papers suggesting that pollution has a negative impact on health.
But does this damage extend beyond our physical health, to negatively affect learning?
Ludovica Gazze is an environmental economist and assistant professor at the University of Warwick, and she says the data to confirm this is already piling up.
For decades, she explains, there has been increasing evidence to show a correlation between pollution levels and school absences.
A study published by the University of Utah in the US in 2020 found that the number of school absences in the Salt Lake City School District usually doubles the day after a “red air day”: when ambient or outdoor air quality levels have reached unhealthy levels.
Pollution is measured in terms of something called particulate matter (PM), which tells you the size of potentially toxic particles in the air.
PM10 particles are larger particles that can irritate your eyes, nose, and throat, while PM2.5 particles are smaller, and potentially more dangerous, as they can travel deeper into your lungs, or even into your blood.
After analysing attendance data, the researchers at Utah found that even a slight increase in PM2.5 levels led to a substantial increase in the number of student absences the following day.
“Children’s health is directly affected by pollution,” Gazze explains. “That means that vulnerable kids miss important time in the classroom. And potentially, at home, they might be incapacitated to study or do homework.”
There is evidence, then, that pollution has an indirect effect on pupils’ learning simply by keeping them out of school. Yet there is also emerging evidence that pollution has a direct impact on cognitive function.
For example, a rapid review, published earlier this year by researchers at the University of Manchester, looked at nine separate studies that investigated the relationship between traffic-related air pollution levels in and around schools, and executive functioning in primary pupils.
Nicola Gartland, a research fellow at the University of Manchester and author on the study, says that while it’s hard to draw firm conclusions, because the studies the team looked at varied in size, context, and measures, “there is relatively good evidence for an effect of particulate matter with a diameter of 2.5 µm or less (PM 2.5) on working memory, attention and academic outcomes”.
The review also highlighted that evidence for the effects of PM10 is limited, but what is available suggests potential wide-ranging negative effects on attention, reasoning, and academic test scores.
More teaching and learning research:
Of course, we know that there are many factors that can affect students’ learning. So, how can the researchers be sure that these negative effects are down to pollution?
“A lot of these studies controlled for things that we would expect to be associated with learning skills and outcomes, like socioeconomic status, sex and age, and parental education level,” explains Gartland. “A lot of them also controlled for pollution at home, to make sure that it wasn’t an exposure that was happening elsewhere.”
Yet, we still need to treat the findings with some caution, she adds: “We don’t yet understand the mechanisms of these effects and more research is needed to explore how pollution interacts with the myriad of influences on cognitive development in childhood.”
Already, the international evidence base is growing. A study published in 2019 by the National Bureau of Economic Research supports the findings from Manchester and goes one step further, to suggest that pollution may have a negative impact on behaviour, as well as on test scores.
Researchers analysed data from schools in Florida between 1996 and 2012 and found that when a child transitions from a school which is “upwind” of a major highway, to one which is “downwind”, and therefore more polluted, test scores decrease by a small amount, while behavioural incidents and absences increase, in comparison to when a child moves to an upwind school.
“Moving schools is a big disruptive event, so we looked at whether there was a specific change for children who moved to a school which is downwind,” explains Jennifer Heissel, who was involved in the study and is now an associate professor at the Graduate School of Business and Naval Postgraduate School in the US.
“On observation, all of the children had similar characteristics, and having statistically dealt with other factors in a variety of ways, we found there were differences, which we attribute to pollution levels,” she concludes.
As well as affecting children throughout their school year, research suggests that cognitive performance during high-stakes exams can be impacted by pollution levels, too.
A paper published in 2016 by Victor Lavy, a professor of economics at the University of Warwick, and others looked at the performance of Israeli students between 2000 and 2002, and concluded that “transitory PM2.5 exposure is associated with a significant decline in student performance”.
The evidence that pollution negatively affects cognition, then, is mounting. But why, exactly, does pollution cause those effects? That is hard to say, says Gazze.
“We do know that our bodies physically react to exposure to pollution. Pollutants, both lead and other toxins, act as an inflammatory agent in the human body and stress hormones spike during an exposure to pollution, which causes humans to go into panic mode,” she explains.
“We are now starting to understand a bit more about how the brain works. The finest particulate matter can cross the blood-brain barrier, and obfuscate or literally fog up some brain processes, and slow down those cognitive processes.”
It’s a starting point, but this needs to be examined further, and urgently. Although particulate pollution levels have been on a downward trend in the UK in recent years, those levels vary depending on where you are in the country, meaning that children living in more polluted areas could be at a disadvantage from their peers in other parts of the country.
Gazze is currently working on a project in the UK with others to find out more about exactly how, and why, pollution affects the brain.
We have a partial answer, then: does pollution affect learning? Yes, it would seem so. Why, and what can we do about it? On those points, research is ongoing to find out.
