Does pollution make you less smart?

Would you believe that breathing dirty air isn’t just a physical hazard – it also seems to make people less intelligent?

This is the surprising conclusion from an international team of researchers after examining 20,000 people in China.

The subjects were of different ages, but they all took a set of language and arithmetic tests – first in 2010, then tests of equivalent difficulty in 2014.

The team compared two sets of scores taken by each examinee and then matched them with air-quality data where he or she lived.

The results suggest the impact of dirty air on intelligence is “huge”.

Across all participants, increases in pollution were associated with significant falls in test scores – a

1mg rise in pollution being equivalent to losing more than a month of education.

The effect was most marked among men, the elderly and those with low education levels (who are more likely to work outdoors).

“Cognitive decline imposes a huge burden on the society,” said researcher Xiaobo Zhang of Peking University in Beijing.

“Although the air quality is getting better, there are bigger problems down the road.”