Highest figures of hazardous ozone in two decades recorded in HK in 2018, despite overall improved air quality

12-Jan-2019 Intellasia | South China Morning Post | 6:00 AM Print This Post

Hong Kong saw its highest average annual concentrations of hazardous ozone in nearly two decades last year, officials have said.

People in Yuen Long, Tuen Mun and Tung Chung were breathing the unhealthiest air, according to air quality data released by the Environmental Protection Department on Friday.

This could be the result of weather conditions such as more sun, less cloud cover and rain, and slightly warmer temperatures.

These conditions have made it more favourable for ozone to form through a reaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the air and under sunlight, which can cause or aggravate respiratory diseases at elevated levels.

Ozone is one of the most harmful types of air pollution, and can cause respiratory diseases.

“The rise in our roadside and urban ozone in recent years could be attributed to high regional background ozone and a fall in local NOx emissions from vehicles, which results in less nitric oxide to react with and remove ozone,” Dave Ho Tak-yin, assistant director of Environmental Protection, explained on Friday.

“So even if we reduce the amount of NOx emissions, it doesn’t necessarily mean that the ozone level will be lowered.”

He said that a sustained regional effort to reduce NOx and VOCs would in the long run help bring down the overall ozone level and its excesses in Hong Kong.

Clocking in at 52 micrograms per cubic metre, the ozone figure was slightly up on 2017′s record high of 51 micrograms.

The record-high level of ozone is not the only problem.

Dominant nitrogen dioxide (NO2) which emanates from motor vehicles, especially diesel-powered ones was down on 2017, but still above the level of the government’s target.

Roadside concentrations of NO2 fell 4.8 per cent to 82, still more than double the annual air quality objective target of just 40.

On the bright side, the department said the overall air quality in the city improved last year.

In 2018, hourly health risk levels graded high or above were recorded at general stations on 2.1 per cent of the days of the year; down from 3 per cent in 2017.

Principal environmental protection officer Kenneth Leung Kai-ming ruled out the possibility that smog might have drifted from northern China, or that the pollution could have been caused by building work on major infrastructure in the region, including the Hong Kong-Zhuhai-Macau Bridge.

Data from the department showed that from 2013 to 2018 the concentrations of major pollutants including particulate matter (PM2.5 and PM10), nitrogen dioxide, and sulphur dioxide in ambient air have reduced by 28 per cent to 54 per cent.

The concentrations of the same pollutants at roadsides have fallen to 36 per cent, a 32 per cent dip from five years ago.

The government also announced that, to further improve the city’s air quality, it plans to review its emission reduction targets, transport planning and management, use of clean fuel and use of renewable energy.

The measures are likely to produce results by 2025, the department promised.



Category: Hong Kong

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