Hong Kong's air quality will suffer if bureaucrat once again heads environment department

We refer to the report, "Appoint a professional to head Hong Kong's environment department rather than a bureaucrat, say advisers" (September 19).

We strongly support calls for the new head of the Environmental Protection Department to be someone with professional expertise when the incumbent retires.

Environmental management requires trade-offs and compromises. Nonetheless, scientific evidence tends to be complex and involve uncertainties, while in the short term, political and economic costs may appear simple and compelling. Under such circumstances, as Melonie Chau Yuet-cheung of Friends of the Earth noted, "scientific evidence often takes a back seat". This is more likely when the person making the final decisions lacks the required scientific background.

For example, the department is considering cutting back its chemical "speciation" network for PM2.5, arguably the pollutant contributing the greatest environmental health risks in Hong Kong. There are many sources of PM2.5, including marine shipping, power plants, vehicles, off-road diesel engines, commercial cooking and outflow from the mainland. We must compare chemical characteristics from different sites to determine the contributions of different sources to the measured PM2.5 concentrations. Cutting back this network will severely limit our ability to determine where the pollutants came from or design effective control strategies against them.

The science is well understood by professionals. One of the first steps the mainland took when it started to take air quality seriously in 2013 was to enhance its PM2.5 speciation capability. In Hong Kong, thanks to more forward-looking professionals in the department, it has been gathering such information for over a decade. This data was critical for the science behind the Clean Air Plan in 2013 and the subsequent HK$11.3 billion vehicle control programmes. It is incomprehensible that when governments elsewhere are trying to better understand the sources of PM2.5, the department is considering cutting that back.

In recent years, we have noticed changes in the department's top-level decision-making. The hard-earned scientific and professional culture that used to make it a professional department, respected by colleagues and academics globally, has become noticeably weaker.

We urge the government to return to a professional-led department and reverse this move away from science-based assessment and decision-making. This is essential if the department is to keep its reputation as a respected organisation that we trust to get the science right when developing policy recommendations and programmes.

Alexis Lau, professor, and Bill Barron, adjunct associate professor, division of environment, Hong Kong University of Science and Technology