Smog set to stay for years as ozone rises

Environmentalist criticises government for blaming Guangdong and dry weather for increase in pollutant when cap on vehicle emissions will work

The city’s notorious smog will plague Hong Kong for years to come as the biggest pollutant contributing to it – ozone – is still on the rise.

The concentration level of ozone hit a record high of 0.058 milligram per cubic metre on average last year, according to research by the regional air quality monitoring network, a 10 per cent year-on-year increase and a 21 per cent rise since the network began its monitoring in 2006.

While the Environmental Protection Department was keen to take credit for reducing other pollutants, it blamed dry weather and rapid development in Guangdong province for the unprecedented ozone levels.

But a leading environmentalist criticised the government for shifting the blame and urged it to adopt more drastic measures to reduce ozone – a main component of photochemical smog and a pollutant that can trigger asthma. Ozone is formed through a photochemical reaction between nitrogen oxide and volatile organic compounds under sunlight.

Ozone is the only one of four pollutants monitored by the network that is on the increase. It also measures sulphur dioxide and nitrogen dioxide, which fell 4 per cent and 7 per cent respectively last year compared with 2010. The fourth, respirable suspended particulates, remained at the same level.

Since 2006, the pollutants have been reduced by 49 per cent, 13 per cent and 14 per cent, respectively.

“The reduction is encouraging. It shows measures taken by both sides to improve air quality are working,” the department’s deputy director, Andrew Lai Chi-wah, said. But Lai blamed the accumulation of ozone on dry weather and the influence of Guangdong. “We had less rain and very high temperatures last year. We also saw a 10 per cent GDP growth in Guangdong,” he said, adding that the problem was difficult for Hong Kong to solve alone.

Dave Ho Tak-yin, a principal environmental protection officer, said the Observatory recorded 38 per cent less rainfall and 16 per cent more sunlight last year.

Ho said the problem could not be resolved quickly due to air pollution in the Pearl River Delta, adding: “The ozone spreads to Hong Kong with the monsoon.”

But Man Chi-sum, the chief executive of the environmental group Green Power, said traffic, not the weather, was the key factor in ozone levels. “Weather can be influential but it is not the most critical factor,” he said. “Hong Kong has much room to reduce ozone by cutting the level of nitrogen oxides.”

Man urged the incoming administration to impose a cap on the emissions of bus fleets, like it did for power plants, as diesel vehicles were a major source of nitrogen oxide. Other measures suggested in the past, such as electronic road pricing and setting up low-emission zones, should also be reconsidered, he said.

olga.wong@scmp.com