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In the study, presence, distribution of 18 polychlorinated biphenyls (PCBs), including 7 indicator PCBs, 12 dioxin-like PCBs (DL-PCBs), and 4 heavy metals (Pb, As, Cd, Hg) have been investigated in Ictalurus punctatus, sediment and water from Jiangsu fish farms; thereafter, risk assessment have been conducted for the ecological risk and human health. The results showed that PCB28, PCB52, PCB114 were the most frequently found pollutants in all collected fish, sediment and water samples. Upon to the different geographical location of fishery farms across Jiangsu Province, components of PCBs presented differently, which implied different pollution sources. The concentration of PCBs found in sediment (178.4-457.2 pg/g) was higher than that detected in water (0.2-11.9 ng/L). Higher concentrations of PCBs was also found in fish meat (1.28-267.96 pg/g), compared to that in fish liver (0.64-95.46 pg/g), and guts and stomach (1.20-45.94 pg/g). Higher content of fat in fish meat could be the possibility of higher enrichment of PCBs compared to the other tissues. Meanwhile, higher concentration of heavy metal was found in sediment than that in water. The total enrichment of heavy metal in fish was found to be Pb﹥As﹥Cd﹥Hg in descend order. Total amount of heavy metals enriched in different tissues were found to be liver ﹥gastrointestinal system﹥meat. All the DL-PCBs TEQ (1.9 pg/g) is less than the maximum residue limit (MRL) of EU (6.5 pg/g). THQ (US, EPA) and R model were employed for the risk assessment by comprising the estimated daily intake and the daily allowed intake. The results revealed that the carcinogenic risk of 18 kinds PCBs and 4 kinds heavy metals remained acceptable level in this study. [ABSTRACT FROM AUTHOR]

[Objectives]This paper aimed to evaluate the validity of pesticides application strategy in rice, and analyse the risk of dietary exposure and ecological impact. [Methods] This study implemented long-term investigation on usage and residual details of pesticides using for pest control in single-season and double-season rice of Jiangsu and Jiangxi provinces. Investigation of pesticides residues in rice and soil had been conducted in the period of tillering, heading and harvesting stage, and the results had been compared between the pesticide reduction strategies adopted area and the regular integrated pest management (IPM) adopted area. Acute and chronic dietary exposed risk and ecological impact risks had been evaluated by using the dietary exposure risk assessment model and the ecology relative risk model (EcoRR). [Results] The results revealed that.4 of total 51 pesticides used in rice for pest control, had been found in the harvest brown rice. Pymetrozine and hexaconazole were the most frequently found pesticides in all rice samples with the frequency up to 93.00% and 28.75%, followed by 14.29% and 7.14% for chlorpyrifos and pentazolidol, respectively. However, the risk assessment of acute and chronic toxicity that may be caused by these 4 pesticides through dietary exposure, was finalized to be negligible for all populations divided by age. Adopting pesticide reduction strategies could further low the risk of dietary exposure. As for the soil sampled from the period of tillering, heading, and harvesting stages of rice, 13 different kinds of pesticides were found, tricy clazole, hexaconazole and propiconazole with 100% detection rates in particular. It could be explained by the long half-life periods of these pesticides and the remains of previous residue. The ecological risk assessment showed that the reduction use of pesticides could decrease the ecological risks significantly, even down to low level from medium level risk. It was found that the most effective effort of reducing the ecological impact was to decrease the use of pymetrozine, as this pesticide played a key role to the contribution of ecological risks in the period of tillering, heading, and harvesting ( 54.16% -83.68%, 19.07%-84.39%, and 0.00%-82.32% respec tively). Secondly, the use of pretilachlor at tillering stage, difenoconazole at the heading stage and propiconazole at the harvest stage was considered to be alternative key elements for the cause of ecological risk, with contributions of the risk ratios of 0.00%-71.50%. 0.00%-68.95% and 1.12%-62.24%,respectively. [Conclusions] Reducing the use of specific pesticides in the particular growth period of rice could reduce ecological impact and dietary exposure significantly. Pymetrozine plays a key role for ecological impact, followed by difenoconazole, propiconazole and pretilachlor, which should be used appropriately. [ABSTRACT FROM AUTHOR]