air pollution
© Cathal McNaughton / Reuters
A new study found chronic exposure to air pollution can take a "huge" toll on one's intelligence. The average impact of breathing in toxic air is the loss of a whole year of education, the study found.

The risks posed by unsafe air to people's physical health are already well documented, as the World Health Organization claims 4.6 million people died in 2016 because of it. But pollution may also have a considerable effect on your intelligence.

The study carried out by researchers from Beijing's Peking University and Yale University in the US analyzed verbal and math test results of 20,000 people of all ages above 10 between 2010 and 2014, comparing them to records of nitrogen dioxide and sulphur dioxide pollution.

It found that the longer people are exposed to pollution, the more impeded their cognitive ability is, and that language becomes more of a struggle than math. It also found men to be more affected than women, especially if from a lower educational background.

"Polluted air can cause everyone to reduce their level of education by one year, which is huge," said Xi Chen at Yale School of Public Health in the US, a member of the research team.

But the study found that those aged over 64 were the ones whose cognitive abilities were hit the most by air pollution.

For the latter, as well as men and those with lower education levels, the cognitive loss "may be a few years of education," Chen said.

As those in their senior years make some of the most important financial decisions regarding retirement and pensions, Rebecca Daniels, from the UK public health charity Medact, said the results are "extremely worrying."

"This is very worrisome as we all know that people often have to make important financial decisions in old age, such as when we should retire, which health insurance plan is better."

The study was carried out in China but the researchers claim it has global relevance given 95 percent of the world's population is living in unsafe air, according to a report by the Health Effects Institute in April this year.