The CEO of the environmental group Clean Air Network on Friday sounded a note of caution over official data showing a dramatic fall in air pollutants in the past decade, saying pollution remained a problem in some densely packed areas of Hong Kong.

Patrick Fung told RTHK's Hong Kong Today programme that the improvements over the past 10 years were down to efforts by scientists, the community and the previous two governments, but more work was needed to maintain them.

The Environmental Protection Department released data on Thursday showing that the average general concentration levels of major air pollutants – nitrogen dioxide, fine suspended particulates (PM 2.5), respirable suspended particulates (PM 10), and sulphur dioxide – dropped by 43 to 62 percent between 2013 and 2022.

The average roadside concentration levels of major air pollutants, meanwhile, fell by up to 64 percent during the same period.

But Fung said: "Questions should be made on what the current administration of government aim to do in order to sustain the improvement, but there are also other worries.

"The EPD also admitted that, in certain districts such as Kwun Tong, Sham Shui Po, Kwai Chung, the air pollution level was still high," he told RTHK's Vicky Wong. "And these are areas with high population density.

"Also the regional ozone is still a big threat, unresolved and as far as we know, there is no regional pollution target set for 2025 and 2030, and there is no action plan agreed among the [Greater Bay Area] cities, so these are areas we should work harder."

Announcing the figures on Thursday, EPD officials acknowledged that reduced traffic during the Covid pandemic had helped reduce the level of pollutants, though they were confident that improvements would continue thanks to stringent emission-reduction measures and the increasing prevalence of electric vehicles.

While all pollutant levels met local air quality standards last year, only one of them, sulphur dioxide, met goals set by the World Health Organisation.

The principal assistant secretary for environment and ecology, Kenneth Leung, said the reduction of other pollutants – such as nitrogen oxides – would take time, adding that cooperation from mainland authorities was required to cut concentration levels of suspended particulates and ozone.