In this study, a comprehensive analysis of the health risks from toxic air pollutants (TAPs) in Hong Kong was conducted. The level and decadal trend (2000-2011) of the health risk from the evaluated TAPs were analyzed. In addition, the risk-based prioritization of TAP sources was conducted.

Among the 59 cancer-risk-presenting TAPs, 19 were associated with inhalation cancer risk (ICR) above 10 per million. In particular, diesel particulate matter (DPM) contributed to 47% of the overall cancer risk, much larger than the contributions from other toxic species. Only copper and formaldehyde were found to pose significant non-cancer risks with hazard quotients larger than one. Based on the risk estimates, we classified the 124 evaluated TAPs into four different priority groups (very...[ Read more ]

In this study, a comprehensive analysis of the health risks from toxic air pollutants (TAPs) in Hong Kong was conducted. The level and decadal trend (2000-2011) of the health risk from the evaluated TAPs were analyzed. In addition, the risk-based prioritization of TAP sources was conducted.

Among the 59 cancer-risk-presenting TAPs, 19 were associated with inhalation cancer risk (ICR) above 10 per million. In particular, diesel particulate matter (DPM) contributed to 47% of the overall cancer risk, much larger than the contributions from other toxic species. Only copper and formaldehyde were found to pose significant non-cancer risks with hazard quotients larger than one. Based on the risk estimates, we classified the 124 evaluated TAPs into four different priority groups (very high, high, moderate, and low priority) to highlight the urgent need for their control.

The downward trend on additive ICRs of TAPs was attributed to the significant decreasing of ICR from DPM. For other TAPs, the ICR has been relatively constant before 2007 and began to decrease thereafter. The identified local source driven TAPs continuously contributed approximately 70% of the total ICR posed by non-DPM TAPs. In addition, the defined local source driven TAPs continuously contributed approximately 60%-70% of the total inhalation hazard index (IHI) posed by TAPs at the two stations.

For PM₁₀, vehicle exhaust source was the dominant ICR contributor (57%), whereas trace metals, residual oil combustion, coal combustion/biomass burning, and vehicle exhaust sources contributed approximately 70% of PM₁₀ IHI. For VOCs, industrial emission 2 (petrochemical) & biogenic emission (36%) and industrial emission 1 (25%) sources were the dominant ICR contributors, while industrial emission 1 and consumer and household products contributed approximately 55% of the additive IHI.