Abstract
Heavy metals in size-segregated particulate matter (PM) were investigated in a Chinese megacity, and an advanced model was developed to&#160;quantify&#160;source-specific risks focusing on size-segregated respiratory exposure.&#160;Incremental lifetime cancer risk (ILCR) and non-cancer risk (hazard quotient: HQ) based on deposition concentrations of heavy metals displayed a peak at 4.7&#8211;5.8 &#181;m. The percentage contributions to cancer risk were&#160;as follows: industrial emission (IE, 34%) > secondary and transport (ST, 29%) > resuspended dust (RD, 21%) > coal combustion (CC, 11%) > traffic emission (TE, 4%) during spring and summer (SS),&#160;and CC (31%) > ST (26%) > IE (21%) > RD (11%) &#8776;&#160;TE (11%) during autumn and winter (AW). RD (41% of HQ during SS, 28% during AW) and IE (45% of HQ during SS, 35% during AW) dominated non-cancer risk. ILCR and HQ of CC were high at sizes 1.1&#8211;2.1 &#181;m and 0.43&#8211;0.65 &#181;m; those of RD were high at sizes >3.3 &#181;m; and those of IE were bimodal at fine (<2.1 &#181;m) and coarse (>2.1 &#181;m) sizes, respectively.&#160;Cancer risk was more susceptible to small particles than non-cancer risk, partly because higher ILCR was from CC, but higher HQ was attributed by RD.
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