Ozone, summer's No 1 enemy, on rise

Warm days come with a downside, as masks can't stop pollutant at ground level in Beijing

Excessive ozone gas has become the prime pollution problem in Beijing in recent days, replacing the notorious PM2.5, and it's likely to linger for a couple of days, the capital's environmental monitoring authority said on Monday.

Because of the sunshine, many residents may not have noticed that ozone reached an alarming 242 micrograms per cubic meter at 2 pm on Sunday, according to the Beijing Environmental Monitoring Center.