The Environmental Protection Department on Thursday said it expects Hong Kong’s air quality to continue improving, despite an expected increase in traffic following the full reopening of the border.

Government data showed 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.

Stephen Siu, an assistant director of the department, said the improvement was due in part to reduced activities during the Covid outbreak.

"But actually we do not foresee that Covid-19 will affect the long-term improvement trend of [air] quality in Hong Kong,” he said.

Even though the full border reopening is expected to bring about heavier traffic, Siu said he still believes the local air quality will continue improve, thanks to the introduction of 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 – takes time.

He added that it requires the cooperation of mainland authorities to cut concentration levels of suspended particulates and ozone.