Pollution And Risk Assessment Of Polychlorinated Biphenyls In Paddy Fields Of Abandoned E-Waste Dismantling Sites

The rudimentary recycling of electronic waste(e-waste)has been banned in China since the heavy environmental pollution it caused,leaving many abandoned e-waste sites.Traditional agricultural activities such as rice planting are still practiced at such sites;knowledge is limited on the ecological and health risks of e-waste derived contaminants.Polychlorinated biphenyls(PCBs)are one group of the most important pollutants in the local environment of abandoned e-waste sites.In the present study,we detected the levels of PCBs in the soil,apple snails and rice grains collected from paddy fields of abandoned e-waste sites in South China.We examined the bioaccumulation characteristics of PCBs in apple snails and assessed the dietary exposure to PCBs of the local residents through rice consumption.Furthermore,we evaluated the temporal trends of PCB levels in the apple snails and rice grains following the stricter environmental regulations.The mean ?PCBs concentrations in apple snails(53 ng/g dry weight)was nearly9-fold higher than that detected in the reference samples.The result suggests that the abandoned e-waste recycling site is still heavily polluted by PCBs,despite of the fact that crude e-waste recycling processes have been prohibited.Both concentrations and profiles of PCBs in apple snails resembled those in paddy soils,suggesting that apple snails can be used as an ideal bioindicator for PCBs.Field determined biota-soil accumulation factors(BSAFs)for PCBs ranged from 0.31 to 1.9,with most of the values being 1–2;indicating that theoretical BSAFs could be used to predict the bioaccumulation of PCBs in the snails with a reasonable degree of certainty.The mean concentrations of ?PCBs in rice grains from 4 abandoned e-waste sites varied from 2.98 to 30.8 ng/g;which were one to two orders of magnitude higher than those examined at a control site.The average estimated daily intakes(EDIs)of ?PCBs via rice consumption under a median exposure scenario ranged from 18.0 to 184 ng/kg bw/d for adults and from 34.1 to 350 ng/kg bw/d for children,which has approached or even exceeded the threshold values for assessing human health effect(20 ng/kg bw/d).The results of associated health risks assessment showed that the local residents of abandoned e-waste recycling sites may have the potential for adverse human healthimpacts arising from dietary exposure to PCBs due to rice consumption and is of a currently great concern.The concentrations of ?PCBs in apple snails decreased significantly after the bans of crude e-waste recycling activities,but there were no significant differences in rice grains.