Lower concentrations of harmful pollutants were recorded last year but roadside-dominant nitrogen dioxide remains a headache for the city
Lower concentrations of harmful pollutants were recorded last year, including the tiny particulates that can penetrate deep into the lungs – but roadside- dominant nitrogen dioxide remains a headache for the city, with most figures failing annual air quality targets.
And while ambient concentrations of hazardous ozone fell for the second consecutive year, they are proving stubbornly hard to cut having increased 15 per cent since 1999.
The preliminary air quality data for 2016 was released by the Environmental Protection Department yesterday.
At roadsides, concentrations of respirable suspended particulates (PM10) dropped by 15 per cent, fine suspended particulates (PM2.5) by 12 per cent, and sulphur dioxide
(SO2) by 10 per cent.
Similar drops were recorded at general stations. Fewer hours and days of high health risk air were recorded at both ambient and roadside stations last year.
But although roadside concentrations of nitrogen dioxide (NO2) – a product of fuel combustion – fell by 17 per cent, the average annual concentration of 82 micrograms per cubic metre of air was still more than double the annual air quality objective target of just 40.
All three roadside monitoring stations also fell short of the air quality objectives for acceptable annual NO2 levels last year.
“Roadside NO2 remains a very big challenge as reduction technologies available now are not that sophisticated,” assistant director of air policy Mok Wai-chuen said.
At roadsides, concentrations of respirable suspended particulates (PM10) dropped by 15 per cent, fine suspended particulates (PM2.5) by 12 per cent, and sulphur dioxide
(SO2) by 10 per cent.
Similar drops were recorded at general stations. Fewer hours and days of high health risk air were recorded at both ambient and roadside stations last year.
But although roadside concentrations of nitrogen dioxide (NO2) – a product of fuel combustion – fell by 17 per cent, the average annual concentration of 82 micrograms per cubic metre of air was still more than double the annual air quality objective target of just 40.
All three roadside monitoring stations also fell short of the air quality objectives for acceptable annual NO2 levels last year.
“Roadside NO2 remains a very big challenge as reduction technologies available now are not that sophisticated,” assistant director of air policy Mok Wai-chuen said.
He believed improvements in particulate pollution were a result of policy measures such as an ongoing scheme to phase out old diesel commercial vehicles progressively and new laws requiring ships at berth to switch to low- sulphur fuel.
“This proves our policies to tackle particulate matter have been effective,” he said, adding that other measures such as tightening emission controls are being looked at.
Mok claimed the most severely polluted days were a result of ozone, a regional problem, either from pollution blowing in from the Pearl River Delta or meteorological
conditions such as tropical cyclones.
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 – which gives a dusk sky a lurid, orange tint – and at elevated levels, can cause or aggravate respiratory diseases.
Asked if the toxic smog plaguing northern China could have drifted south, he said “it could not be ruled out” but “was of low possibility”.
The Clean Air Network’s Loong Tsz-wai said Mok’s meteorological explanations diverted attention from the most pressing issue, which was roadside pollution and the
“uncontrolled growth” of road vehicles.
“Most of our exposure to bad air is at roadside,” he said. “NO2 concentrations may be going down but the effectiveness of exhaust pipe policies could be easily offset over the years if the number of private cars is not curbed.”
Wang Tao, chair professor of atmospheric environment at Polytechnic University, said the increase in regional ozone had indeed slowed since 2013, but not fallen. More control of precursors, such as VOC and NOX, were needed on both sides of the border, he said.
Source URL: http://www.scmp.com/news/hong-kong/healthenvironment/article/2059691/hong-kong-enjoys-breath-fresh-air-its-not-enough