Is air pollution making us dumb?

As per new research conducted in China, air pollution leads to a significant reduction in our cognitive abilities, thereby indicating that the damage is not only restricted to our hearts and lungs. Exposure over longer periods of time correlated with larger drops in performance, and the effects were most pronounced for men and older people. " This decline in verbal scores was especially notable in older, less educated men, which researchers say could have effects on the economy as well".

'If we calculate [the loss] for those, it may be a few years of education'.

Smoke rises above the skyline of Beijing on a gorgeous polluted day in 2017.

Over the course of four years, scientists analysed the maths and verbal skills of around 20,000 people in China.

Researchers used measurements of sulphur dioxide, nitrogen dioxide and particulates smaller than 10 micrometres in diameter in areas where their cohort lived in their comparisons - ozone, carbon monoxide along with larger particulates were not included in the study.

The study estimated that reducing fine particulate matter concentrations to the US Environmental Protection Agency (EPA) standard of 50 microgrammes per cubic metre would increase verbal and math scores.

They found the more exposed people were to polluted air, the greater their cognitive decline was over time. Language ability suffered more than mathematical ability and men were more harmed than women.

The researchers tested the same subjects in 2010 and 2014, and the math and verbal tests were meant to show "different dimensions, representative of the functioning of the brain", Chen said.

"For older persons (in our study those age 55-65 or 65+) the effects can be very hard to mitigate given the long term cumulative exposure", Mr Xi says.

They were given 24 standardised maths questions and 34 word-recognition questions.

However, while establishing a link between pollution and lower test scores, the study did not prove cause and effect. "This can just show a correlation between high pollution levels and lower scores", Dr Vinay Goyal, professor of neurology at All India Institute of Medical Sciences (AIIMS), said.

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

While physical health has always been thought the most common casualty of air pollution, the study is the first to link poor air quality to cognition and an increase the risk of Alzheimer's disease, the most common form of dementia.

The scientists also accounted for the cognitive decline that naturally occurs as people age, as well as the general uncooperativeness and impatience that occurred on test days when pollution was particularly high.