Even “zero emission” HK couldn’t meet WHO air quality guidelines: Under-Sec for Environment

A diesel ferry tacks across a hazy harbour: but removing every pollution source in Hong Kong wouldn’t solve the city’s air quality problems.

Hong Kong could not meet the World Health Organization (WHO) 2005 Air Quality Guidelines (AQGs) by 2025 even if the city cut its domestic pollution to zero, according to the government’s Under-Secretary for the Environment Tse Chin-wan.

“Based on the findings of our air quality assessment, even assuming zero emissions in Hong Kong in 2025, the WHO AQG levels still could not be achieved,” Tse said, speaking at a government-led committee charged with setting new ceilings for Hong Kong’s air pollution laws.

Tse’s comments came to light with the recent publication of the minutes of the Air Science and Health Sub-group of the Air Quality Objectives (AQO) Review Working Group which Tse chairs. During a December 2018 meeting, a committee member challenged the assumptions used in the government’s cost-benefit health analysis, and requested the government’s consultant, AECOM Asia Co., run modelling to determine the health and economic impact of actually achieving the WHO’s 2005 AQGs.

AECOM’s representative, Professor Wong Tze Wai, responded it would be impractical to model such a scenario without first considering the technical feasibility for achieving the targets. “It might not be pragmatic to simply assess the ideal scenario,” he said.

At this point, the Under-Secretary for the Environment concurred that indeed the exercise would be futile, admitting that Hong Kong couldn’t meet the AQGs even if the city was effectively shut down to zero emissions.

“Background” pollution to blame

According to Dr. Kenneth Leung, Principal Environmental Protection Officer (Air Science), Environmental Protection Department (EPD), the background annual PM10 contribution from mainland China is estimated at 30µg/m3, well above the WHO AQG of 20µg/m3. Given the mainland’s slow rate of emissions reduction – 17% over ten years for PM10, according to Leung – the situation is unlikely to improve for the 2020-2025 review period assessed by Tse’s committee.

The WHO says PM10 can remain in the atmosphere for days or weeks and thus be subject to long-range transboundary transport in the air. “There is no evidence of a safe level of exposure or a threshold [of PM] below which no adverse health effects occur. The exposure is ubiquitous and involuntary, increasing the significance of this determinant of health,” it said in a report into the health impacts of particulate pollution.

Responding to an enquiry about Tse’s comments, an EPD spokesman said “Air pollution is an environmental challenge that has no boundaries.” The spokesman said the government planned more collaboration with Guangdong government in the future, but failed to offer details of any specific plans, meetings or collaborations between the two governments when asked.

The spokesman also revealed that Hong Kong will not be considering meeting the WHO 2005 AQGs even by 2030 and will still be working towards the WHO Interim Targets for that date. “We plan to start the next review cycle in 2021 for completion by 2023, to review the Interim goals for 2030,” he said. The WHO designed Interim Targets to help developing nations suffering from extreme pollution manage their pollution reduction in a more systematic way. 

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