Harmful ozone levels drop in Hong Kong, Macau and Guangdong: experts not convinced they will stay that way
Ozone concentrations were 7 per cent lower last year compared to 2014, though 10 per cent up from a decade ago, and still higher than World Health Organisation air quality guidelines
Concentrations of harmful ozone in the region have dropped to the lowest level since 2010 – but air pollution experts are sceptical that a downward trend can be sustained.
Annual results from the Pear River Delta Regional Air Quality Monitoring Network, released yesterday, recorded annual average ozone concentrations 7 per cent lower last year compared to 2014, though 10 per cent up from a decade ago.
The network, which began operations in 2006, collates data from 23 monitoring stations in Hong Kong, Macau and Guangdong province.
Ozone concentrations measured at Tung Chung, Tsuen Wan and Yuen Long fell but increased slightly at Tap Mun. Higher averages were also recorded in rural areas such as Tianhu in Guangzhou and Jinguowan in Huizhou.
All 23 stations recorded daily eight-hour ozone averages higher than the World Health Organisation’s air quality guidelines.
Video: 2014 report on ozone levels rising to the worst in a decade
Ozone is formed through a reaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the air and under sunlight. It is a main component of photochemical smog and at elevated levels, can cause or aggravate respiratory diseases.
“While the increase in regional ozone pollution appears to be slowing , it’s difficult to determine whether this is a downward trend or just a year-to-year drop,” said Professor Wang Tao, an urban and regional air quality expert at Polytechnic University.
“In recent years, NOx has certainly been falling in China as a result of emissions control and technologies at power plants, but VOCs have still been increasing across the delta region.”
Wang said VOC control needed to be strengthened for a sustained decrease in ozone. “But VOC is not as easy to control as NOx, as it comes from diverse sources such as vehicles, factories and even paints and solvents,” he added.
Clean Air Network chief executive Patrick Fung Kin-wai said ozone remained a major regional pollutant and minor emissions control measures could easily be offset by increases in vehicle traffic and large infrastructure projects like the Hong Kong-Zhuhai-Macau Bridge.
Annual averages of sulphur dioxide, nitrogen dioxide, respirable suspended particulates (PM10) fell 19, 11 and 13 per cent respectively last year from 2006 levels.
Fine suspended particulates (PM2.5), measured for the first time last year, clocked in at 32 micrograms per cubic metre, lower than Hong Kong’s targets but three times higher than the WHO’s.
The Environmental Protection Department cited key measures implemented in Hong Kong in recent years such as tighter emission caps for power plants, phasing out old diesel commercial vehicles and making oceangoing vessels switch to cleaner fuel at berth.
Guangdong cited measures such as cleaner power generation, phasing out polluting industries and introducing desulphurisation and denitrification technologies. Macau said it had banned imports of highly polluting vehicles.