STUDENTS exposed to high levels air pollution before taking exams get worse grades according to recent studies.
Two separate studies looked at school kids taking their exams and cross-referenced it with studies of pollution levels in study halls by experts at London School of Economics.
The experts found air quality has as big an impact on results as class size and that high levels of pollutants can lower exam scores by more than three percent.
The researchers studied 2,400 students taking more than 10,000 exam papers.
Dirtier air, or areas with high concentrations of a substance known as PM10, caused performance to drop by around two percent.
The World Health Organisation (WHO) has set advisable limits on matter such as PM10.
The WHO limit for PM10 is 50 micrograms per cubic metre, and the study revealed that some exam halls had pollution levels as high as 75 micrograms.
This was found to be potent enough to reduce a student's score by 3.4 percent.
Another study which took place in Israel looked at around 400,000 exams taken by teenagers there. It revealed that high levels of PM2.5, which is like a finer form of pollution compared with PM10, was linked to poor results.
Sefi Roth, of the London School of Economics had a hand in both studies and told The Times that students should consider their exposure to pollution on the day of an exam.
"They can limit their outdoor activity on polluted days or take less polluted routes when they go to school," said Roth.
A link between pollution and cognitive performance "would imply that a narrow focus on traditional health outcomes, such as hospitalisation and increased mortality, may understate the true cost of pollution as mental acuity is essential to worker productivity in many professions," he added.