One in four green spaces in London breach safety limits for air quality, new analysis has revealed.
The report, published by Imperial College London and the University of Leicester, found 24% of play spaces and 27% of public parks had NO2 limits exceeding safety standards.
The researchers warn this could potentially put thousands of children and vulnerable Londoners at risk.
Dr Daniela Fecht, from the MRC Centre for Environment and Health, said: 'Dangerously high levels of nitrogen dioxide are a genuine concern for people living in the capital, especially for those with children, the elderly and those with poor health.
'We know already that hundreds of primary schools and nurseries are located within, or very close to, areas that exceed legal safety limits for NO2, potentially putting children’s long-term health at risk, but we may think our green spaces are clean.
'Our research shows this is often not the case, with a large number of public and private parks in the capital exceeding legal limits for harmful air pollutants.'