Hong Kong’s air quality saw general improvements in 2018, with levels of most air pollutants keeping within their target limits, except for ozone and nitrogen dioxide.
According to statistics released by the Environmental Protection Department on Friday, levels of ozone rose for the third straight year. The concentration reached 52 microgrammes per cubic metre, the highest level on record since 1999.
Ozone levels surpassed the Air Quality Objectives (AQO) at eight out of 13 monitoring stations last year, said Environmental Protection Department’s Assistant Director Dave Ho.
“The short-term situation of ozone exceeding limits is a rather serious problem, and we need to work with Guangdong Province authorities,” Ho said, noting that some ozone originated from neighbouring areas.
Nitrogen dioxide levels were also recorded to be twice the AQO limit last year, despite the numbers going on a downward trend.
“Roadside concentration of nitrogen dioxide is relatively high, despite going down 30 per cent in the last five years,” Ho added.
Aside from nitrogen dioxide, three major types of air pollutants – namely sulphur dioxide, fine particulates and respirable particulates- were found to be within their AQO limits last year.
The three types of pollutants also recorded a slight dip in concentration.
Air Quality Health Index
The Air Quality Health Index (AQHI) in 2018 also recorded minor improvements. Ho said that the AQHI recorded levels of “high”, “very high” or “serious” for 2.1 per cent of the year, which was less than the three per cent in 2017.
Roadside monitoring stations saw the same figure fall from 4.3 per cent in 2017 to 2.8 per cent last year.
Tung Chung, Yuen Long and Tuen Mun suffered the worst air pollution, with the EPD attributing the cause to their proximity to the Pearl River Delta.
The Environmental Bureau released a clean air plan for Hong Kong in 2013, with target figures to hit by 2020.
Ho on Friday said there was no need to tighten the reduction target for ozone, and that his department will continue to tackle vehicle emissions and other sources of pollutants.
Concern group the Clean Air Network said in response that the government should take responsibility for the high ozone levels.
“Ozone is the by-product of nitrogen oxides and volatile organic compounds. The main reason for ozone levels reaching a 19-year high is that the Environmental Protection Department could not control the high levels of nitrogen oxides,” the group said in a statement on Friday.
“The reason why ozone levels have repeatedly broken records is that the Hong Kong government did not halt the increase in road vehicles, and did not tackle the high levels of roadside air pollution.”