**2.4. Aerosols and effect on quality of life**

The effects of aerosols on the atmosphere, climate and public health are among the central topics in current environmental research. Urban areas have always been known to be a major source of particulate pollution (Finlayson-Pitss, 2000) which is expected to continue to increase due to world population growth and increasing industrialization and energy use, especially in developing countries (Fenger, 1999). The most obvious effects are the contributions to unsightly smogs and visible deterioration of the building materials (Grossi, 2002). In addition, the fact that urban particulate pollution impact directly on human health has been known for centuries (Brimblecombe, 1987) and has been the subject of much research (Adam et al., 1999).

In an attempt to reduce the health burden of atmospheric particulate pollution, regulatory authorities have attempted to place controls on the emission and the magnitude of pollution episodes within conurbations. The monitoring of particulate air pollution has traditionally focused on particles of less than 10 μm in aerodynamic diameter (the PM10 standard), as these are more likely to pass the throat when inhaled (DEFRA, 2005; Larrsen, 1999) but it has become apparent that the smaller particles are more significant, as these particles will penetrate deeper into the lungs and potentially cause more physiological distress or damage. This has lead to the use of the PM2.5 standard in countries such Malaysia, where the total mass of particulate matter less than 2.5 μm in diameter is monitored (MOSTI, 2000).
