As Hong Kong returns to normalcy after the pandemic, air pollution is also making a strong comeback, according to a study by Clean Air Network.

The green group's CEO, Patrick Fung, told RTHK's Hong Kong Today programme that the annual average concentration of ozone in the city reached a record high in 2023, with roadside ozone concentration rising 32 percent.

Many other major pollutants such as nitrogen dioxide, PM10 and PM2.5 also saw double-digit percentage increases, getting close to pre-pandemic levels in 2019.

"The government has been conducting a three-year joint study on the issue of the ozone... it's time for recommendations by the SAR government to tackle the issue... we can't just sit and wait," Fung said.

He added that Southern, Eastern, and Central and Western districts had the highest levels of ozone last year.

Fung said there are a number of health impacts caused by the ozone issue, particularly respiratory diseases, including asthma and allergies.

He added that because we cannot see the ozone, there is a reliance on the indexes provided by scientists and the government.

"I think the government, in the Clean Air Plan 2035, has committed to looking at how to update the AQHI, the Air Quality Health Index, so that both long- and short-term health risks would be addressed, and that includes ozone. So we look forward to hear more."