“We are not suggesting that the Covid epidemic has played no role in improving our air quality, but we can see that we were on the right track for the past 10 years,” Siu said as the department presented its 2022 air quality report.

“Even as economic activities started rising in the latter half of 2022, air quality for the whole year did not get worse.”

According to the report, annual average concentrations of major air pollutants fell in 2022. Roadside PM10 was 29 micrograms per cubic metre, down from 33 in 2021, 31 in 2020, and 38 in 2019. The concentration of roadside PM2.5 was 18 micrograms per cubic metre, down from 20 in 2021, 19 in 2020, and 25 in 2019.

The concentration of nitrogen dioxide dropped to 64 micrograms per cubic metre from 70 in 2021 and 2020 and 80 in 2019.

Kenneth Leung Kai-ming, the principal assistant secretary for environment and ecology, added that the government’s efforts in promoting the use of electric cars could help offset the impact of increased traffic on air quality.

“The government is making efforts to promote the use of electric cars as part of the Clean Air Plan for 2035,” Leung said. “In 2021, the sale of e-cars in Hong Kong was about 9,700, and the number jumped to about 19,700 in 2022. So, the result is, even when traffic flow increases, air pollution can still be reduced when more of our cars are using clean energy.”

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Officials maintained the air quality in the Pearl River Delta region had also reached the cleanest levels since the mid-2000s.

According to the report, the concentration of sulphur dioxide in the region had dropped 86 per cent since 2006, while that of PM10 fell by 55 per cent.

But officials admitted ozone, a greenhouse gas, remained an issue. Ground-level ozone is formed when volatile organic compounds and nitrogen oxides react with ultraviolet light. The key source of these pollutants is vehicle emissions. Ground-level ozone is highest in the afternoon when the sunlight is the strongest.

In 2022, roadside ozone concentration hit 34 micrograms per cubic metre, a 10-year high, up from 31 in 2021.

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Siu maintained it was a “regional” issue and had to be tackled by cooperating with Guangdong and Macau authorities.

According to the department, the governments of the three places were conducting a three-year joint study to understand the origin of ozone formation. The findings would help with devising improvement measures, the department said.

The Hong Kong government plans to set up a supersite for Greater Bay Area air quality and meteorology monitoring.

The Clean Air Network, however, criticised the government for being all talk and no action. On the HK$261 million (US$33.2 million) monitoring supersite, the group said it came too late as it would not be fully operational until 2027 at the earliest.

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The green group cited a study by the University of Hong Kong’s school of public health that unsafe pollution levels in 2022 had caused 3,516 premature deaths and an economic loss of HK$41.9 billion.

Campaign manager Betty Lau Hin also warned air pollution could take a turn for the worse after society returned to normal.

“The government might be too idealistic to think that more e-cars can solve the problem,” said Lau, who suggested a comprehensive approach to the issue that should include more pedestrian and bicycle-friendly policies.