BREATHING in toxic air fumes could increase dementia risk, a study claims.

Scientists found mental decline was greater in people exposed to higher pollution levels.

They fear inhaling poisonous particles and gases could heighten the chances of irreversible damage to the brain.

Previous studies have estimated air pollution causes an estimated 40,000 premature deaths a year in Britain from lung disease and heart attacks.

Now scientists from Beijing University say toxic air also harms the brain. They gathered data from 16,000 households that took part in a three-year health study.

Researchers compared air pollution levels with scores on memory tests and maths questions.

Those exposed to the highest levels of toxic pollutants in the air saw the biggest decline in mental ability.

Men fared worse than women, the study revealed.

The researchers said: “Our findings imply the effect on social welfare could be much larger than previously thought.”