Chinese scientists discover that trees are producing ozone smog in Beijing

Beijing’s hundreds of thousands of weeping willows and poplars have been a welcome source of shelter from the fierce summer sun for more than four decades – but they may also be an unexpected source of pollution, according to new research. Scientists warned that this urban greenery may be “choking” the Chinese capital’s 20 million residents by increasing the levels of ozone in the city’s air. Smog caused by the ozone released by car exhaust has been recognised as a public health problem since...