Recently, hazardous air pollutants (HAPs) have been a serious issue in Korea, mainly because of the public’s increasing awareness of the importance of environmental health. HAPs are different from other conventional air pollutants such as SO
2
,NO
x
, CO, and O
in terms of their carcinogenic properties and non-threshold nature of toxicity. It is well known that long-term exposure to HAPs even at low levels may still have significant negative effects on human health (WHO, 2000). Various classes of organic or inorganic chemicals belong to the HAP category, including volatile organic compounds (VOCs) such as benzene and 1,3-butadiene, polycyclic aromatic hydrocarbons (PAHs), dioxins, pesticides, and some heavy
3