Exposure to toxic air pollution significantly reduces intelligence, according to new research.
The China-based study, entitled 'The impact of exposure to air pollution on cognitive performance', has found that high pollution levels can lead to significant drops in test scores in language and arithmetic.
The average impact was equivalent to having lost a year of the person's time in school.
The damage in intelligence was worst for those over 64 years old, with serious consequences noted by the research team.
While the data was based on China, the international scientific community has reacted to the findings with interest, questioning whether the same was true in the western hemisphere.
Pollution in Malta continues to be among the worst in Europe, with the island having the fourth highest levels of particles in the air compared to all member states.
According to the European Environment Agency, the concentration of fine particulate matter on a day-to-day basis stood at 50 micrograms per cubic metre in 2015, right on the EU daily limit value.
Bulgaria, Poland and Greece were the only countries to fare worse than Malta.
Published in the scientific journal Proceedings of the National Academy of Sciences, the new Chinese research was based on State language and arithmetic tests conducted on 20,000 people across China over a period of four years.
Comparing test results with records of nitrogen dioxide and sulphur dioxide pollution, the researchers found that the longer people were exposed to dirty air, the greater the damage to intelligence.
Language ability was impaired at a higher level than mathematical accuracy and men were found to suffer harmed than women.
The scientists accounted for the gradual decline in cognitive ability which normally occurs as people age.
Air pollution, the research found, could also have a short-term impact on intelligence as well, meaning you could actually be less intelligent on a pollution-heavy day.