Measures to reduce roadside pollution

This was revealed by the Environmental Protection Department which said this could bring down nitrogen dioxide by over 90 percent.

Most taxis and minibuses run on liquefied petroleum gas, or LPG, instead of regular petrol, as they are more environmentally friendly.

But that’s only if the vehicles are fitted with a device called a catalytic converter, which converts toxic exhaust emissions into non-toxic substances.

An assistant director of the Environment department, Mok Wai-chuen, said currently 80 percent of the taxis and 45 percent of light buses using LPG have defective catalytic converters and are emitting pollutants excessively.

The two types of vehicles are said to account for nearly 40 percent of nitrogen oxides and 55 percent of hydrocarbons at busy roads in the urban areas.

Both pollutants are major causes of very high levels of roadside Air Pollution Index readings.

Mr Mok said although the levels of sulphur dioxide and suspended particulates at roadside air quality monitoring stations have decreased since 1999, the level of nitrogen dioxide went up by 20 percent.

Other improvement measures announced by the administration include screening out vehicles in 2013 which emit excessive smoke.

The government said it would consult stakeholders over the next two months before implementing the measures.