Air quality deteriorated last year, with overall levels of nitrogen dioxide, prevalent at roadsides, hitting the second-worst level recorded in the city's history, a concern group report has found.
The figures once again prove roadside emissions from local vehicles could contribute more to bad air than external pollution from widely blamed sources such as coal-fired plants in the Pearl River Delta.
Overall levels of average nitrogen dioxide concentrations recorded at the city's three roadside monitoring stations hit 121 micrograms per cubic metre in 2013, up from 119 in 2012 and the record 123 in 2011, according to the Clean Air Network (HKCAN). Since 2006, overall roadside nitrogen dioxide emissions rose about 24 per cent.
And last year's spike in nitrogen dioxide concentrations was largely driven by readings at the roadside station in Central, which hit a record high of 126 micrograms per cubic metre, the report found. The other two roadside stations - Causeway Bay and Mong Kok - recorded equally alarming figures of 121 and 116, respectively.
Both the World Health Organisation and the city's new Air Quality Health Objectives stipulate 40 micrograms per cubic metre as the acceptable level of average nitrogen dioxide concentration each year.
The three roadside monitoring stations also exceeded WHO levels of particulate matters (PM10) and fine particulate matters (PM2.5) - tiny specks of pollutants small enough to penetrate the lungs and cause cancer. Monitoring stations at Kwai Chung and Tsuen Wan recorded the highest level of sulphur dioxide among all stations.
HKCAN chief executive Kwong Sum-yin urged the government to highlight the link between traffic issues and pollution in the upcoming policy address and to "look into the problem from a comprehensive transport management perspective".
"It's time for the Transport and Housing Bureau to act," Kwong said. She recommended regular progress reports on the HK$11.4 billion initiative to replace old commercial diesel vehicles, which was approved by the Legislative Council financial committee yesterday.