Author: Antonio Da Roza

Date: 12/8/10

Particulate matter as a primary pollutant

Combustion sources, in particular diesel vehicle exhaust and emissions from power plants, are the major local sources of particulate matter (PM). To a lesser extent, crustal dust and marine aerosols are also sources of PM. PM with particle sizes less than 10 microns are known as respirable suspended particulates (RSP) or PM10. Regional sources also contribute to local PM levels. [1]

Particulate matter and electricity generation

Public electricity generation is one of the major sources of RSP emissions which contributed to 28% of total emissions in 2007. In 1994, nuclear electricity from Daya Bay was imported which decreased emissions of RSP. Since 1995, the use of natural gas for power generation was introduced which resulted in a downward emissions trend as well. In 2003 and 2004, the RSP emissions increased due to the increased power generation from coal-fired units. [2]

Since 2005, emission caps had been set which helped reduce RSP emissions. Emissions in 2007 decreased by 14% from 2006. [2]

Particulate matter and road transport

Road transport is one of the major sources of RSP emissions which contributed to 30% of total emissions in 2007. A series of control measures were implemented to help reduce RSP emissions in recent years, including the progressive tightening of vehicle emission standards from Euro I to Euro IV from 1995 to 2006, the incentive scheme to replace diesel taxis with LPG in 2000, the incentive scheme to replace diesel minibuses with LPG/ electric in 2002 and the incentive scheme to install particulate filter at pre-Euro diesel vehicles from 2002 to 2005. In 2007, the schemes encouraging owners to phase-out their pre-Euro and Euro I commercial vehicles earlier also helped reduce their emissions. [2]

Particulate matter as a secondary pollutant

Particulates (PM) can be formed by atmospheric oxidation of SO2 and NOx. [1]


  1. 1.0 1.1 ‘Air Quality Objectives Review Public Consultation’, Environmental Protection Department Hong Kong, July 2009 - last accessed 5/8/10
  2. 2.0 2.1 2.2 ‘Air pollutant emission inventory’, EPD website – last accessed 12/8/10