| With the accelerating pace of urbanization and industrialization in China, a huge number of migrant workers work in high-polluted industries and live in contaminated environment. Therefore, they are facing high health risk of occupational exposure and daily life exposure. However, the quantitative research in this aspect is very little. The city of Taizhou in eastern China is one of the world's biggest e-waste recycling centres. The local environment is seriously polluted by polychlorinated biphenyls (PCBs) et al. The previous studies focused on the dietary exposure, but the local foodstuff and drinking water come from unpolluted area. In this study, a village of Taizhou where migrant workers gather was surveyed. The corresponding exposure factors of migrant workers and local residents were investigated; the ambient air, indoor air/dust, and domestic water were sampled and analysed the PCB concentrations and the characteristic of congener composition of them; assessed the health risk of the two groups by the methods of US EPA (1989), and provided the guidance for them to avoid the environmental risk. The main results are as followings:(1) The method of combining questionnaire and enquiry was used to investigate the daily activity patterns and the time spent in different sites of the two groups (50 households, respectively), and exposure factors of the two groups were obtained. The results showed that the migrant workers do some heavy labour like dismantling, while the local residents almost do not do the dismantling work. The time local residents spent indoors is more than that of migrant workers.(2) The ambient air, indoor air/dust, groundwater and tap water were sampled and analysed, the results were as follwings:the concentrations of PCBs in the ambient air in industry park of e-waste dismantling (103.58 ng/m3) were much higher than those in residential area (26.76 ng/m3). The PCB concentration in the air and dust in dismantling workshops is 95.71 ng/m3 and 14765.8 ng/g, respectively. The PCB concentrations in indoor air in migrant workers'houses (61.98 ng/m3) were higher than those in local residents'houses (43.10 ng/m3) (p>0.05); The PCB concentrations in indoor dust of migrant workers'houses (63799.3ng/g) were significantly higher than those of local residents'houses (1954.2 ng/g) (p<0.05). The concentration of PCBs in groundwater was 0.1304?g/L, which exceeded the guideline value for PCBs in centralized drinking water-surface water (0.02?g/L). The PCBs in tap water were not detected.(3) The characteristic of PCBs congener composition in different environment media is not all the same. The PCBs in air showed that Tri-CB and Tetra-CB are the main congeners, especially the proportion of them is about 80.1-86.4% in gas-phase. As for dust and groundwater, the low-chlorinated CB level is approximately same with high-chlorinated CB level, and the proportion of high-chlorinated CB increased compared with air.(4) The methods of US EPA (1989) were used to assess health risk of PCBs exposure, while some adjustment of the relevant model parameters was made according to actual situation.The total cancer risk and hazard quotient of migrant workers via exposure to PCBs in air, dust and groundwater was 2.52×10-5 and 1.90, far beyond the acceptable risk level. The total cancer risk and hazard quotient of local residents via exposure to PCBs in air and dust was 5.82×10-6 (beyond the acceptable risk level) and 0.44, respectively. The health risk of migrant workers was 4.3 times higher than that of local residents, which indicated that the population with lower economic status always trend to undertake higher environment risk. The migrant workers are becoming the environmentally vulnerable groups in China.The highest health risk resulted from occupational exposure for migrant workers, and the contribution rate was 74.6%; indoor exposure in the main source of health risk of the local residents and the contribution rate was 68.1%. Inhalation exposure is the leading exposure pathway for migrant workers and local residents, and the rate of contribution was 82.4% and 92.8%, respectively, and that of dermal exposure was 17.6% and 7.2%.(5) For local residents, the indoor exposure and the inhalation exposure pathway are the main causes for health risk, but it is difficult to avoid them. So, cutting off the pollution sources and carrying out environment remediation are the important measures to reduce the health risk; For the migrant workers, to decrease the occupational exposure risk, they should enhance the safety protection; to reduce the daily life exposure, except for the above measures, they should modify some lifestyles, such as stopping dismantling activity near their houses and stopping using groundwater. |
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