| Backgrounds:In recent years,crayfish farming and consumption of China has been increasing,and the crayfish industry chain has been increasingly improved.China has become the largest nation for crayfish production and consumer,and the middle and lower reaches of the Yangtze River is the main producing area of crayfish in China.Crayfish are omnivorous in diet and have strong adaptability to the environment.Therefore,they do not have high requirements for the environment for growth and reproduction and may be exposed to heavy metal pollution.Therefore,this study collected samples of crayfish and its culture environment in the middle and lower reaches of the Yangtze River for several times,analyzed the contents and tissue distribution of heavy metals in crayfish in different regions and links,and explored the health risk levels and accumulation rules of heavy metals in crayfish.Methods:1.Sample the areas with the largest output of crayfish in each production link.The samples of crayfish were dissected into four parts:head shell,back shell,hepatopancreas and muscle.All samples were homogenized,and then digested by microwave digestion instrument before digestion.Four heavy metal elements of cadmium,chromium,mercury and lead were detected by ICP-MS.The results were statistically analyzed to understand the status of heavy metal pollution and the distribution of heavy metals in crayfish in different areas and links.2.The collected environmental samples were pre-treated and tested in accordance with the national standard.Pearson correlation analysis was conducted between the determination results of environmental samples and those of crayfish in the farming process,and a circulating water system was established to conduct culture and exposure experiments on crayfish,so as to explore the accumulation rule of heavy metals in crayfish.3.By calculating Estimated Daily Intake（EDI）,Target hazard quotients（THQ）and Target Cancer risk（TR）of the residents in the middle and lower reaches of the Yangtze River,the dietary exposure of Cd,Cr,Pb and Hg in the crayfish of the residents in the middle and lower reaches of the Yangtze River was analyzed to evaluate the food safety of the crayfish in the middle and lower reaches of the Yangtze River.Results:1.Heavy metal pollution level of crayfish in the middle and lower reaches of the Yangtze River（1）Heavy metal pollution in each link of the crayfish industry chain in the middle and lower reaches of the Yangtze River is as follows:The contents of chromium,cadmium,lead and mercury in cultured crayfish ranged from 0.097-1.739 mg/kg,0.008-0.121 mg/kg,0.037-0.958 mg/kg and 0.004-0.033 mg/kg.The contents of chromium,cadmium,lead and mercury in circulation crayfish samples ranged from 0.201-7.782 mg/kg,0.019-0.183mg/kg,0.066-0.862 mg/kg and 0.006-0.037 mg/kg.The content of chromium,cadmium and lead in processing crayfish samples ranged from 0.087-7.383 mg/kg,<LOD-0.139mg/kg and<LOD-0.326 mg/kg,mercury content range in 0.007-0.075 mg/kg;The contents of chromium,cadmium,lead and mercury in crayfish samples in catering were in the range of 0.085-0.594 mg/kg,0.008-0.306 mg/kg,0.025-0.579 mg/kg,and 0.005-0.045 mg/kg.（2）Heavy metal pollution levels of crayfish in all sampling areas:The cultured crayfish in Shayang County of Hubei Province had the highest chromium content,with an average of 0.948 mg/kg and the highest of 1.739 mg/kg;The average cadmium content of crayfish in Qianjiang city of Hubei Province was 0.096 mg/kg,and the highest value was0.121 mg/kg.The average lead content of crayfish in Huoqiu County,Anhui Province was the highest（0.280 mg/kg）.Shishou city in Hubei Province had the highest average mercury content of 0.026 mg/kg,while Jianhu City in Jiangsu Province and Huoqiu County in Anhui Province had the lowest mercury content of 0.007 mg/kg.（3）The average contents of Cr,Cd,Pb and Hg in crayfish head shells were 0.444,0.025,0.093 and 0.008 mg/kg,respectively.The average contents of Cr,Cd,Pb and Hg in crayfish shells were 0.264,0.098,<LOD,and 0.013 mg/kg,respectively.The average contents of Cr,Cd,Pb and Hg in hepatopancreas of Crayfish were 0.101,0.296,0.025 and0.007 mg/kg,respectively.The mean contents of Cr,Cd,Pb and Hg in crayfish muscle were 0.055,<LOD,<LOD and 0.019 mg/kg,respectively.（4）There are significant correlations between chromium and lead（r=0.6689）,cadmium and mercury（r=0.5332）detected in this paper;However,there was no significant correlation between chromium and cadmium（r=-0.0224）,chromium and mercury（r=0.0462）,cadmium and lead（r=-0.0074）and mercury and lead（r=-0.1609）.2.Study on the accumulation of heavy metals in crayfish.（1）The contents of Cr,Cd,Pb and Hg in crayfish aquaculture water were:<LOD-2.962,<LOD-0.135,<LOD-3.570 and<LODμg/L;the contents of Cr,Cd,Pb and Hg in crayfish culture soil were 67.576-126.603,<LOD-0.590,27.766-55.210 and<LOD-0.204mg/kg.（2）Pearson correlation analysis showed that there was no significant correlation between the heavy metal content in crayfish and the heavy metal content in the corresponding culture environment（water and soil）.（3）The water phase cadmium exposure experiment showed that the higher the concentration of cadmium in water,the faster the accumulation of cadmium,the longer the exposure time,the more accumulation;but to a certain extent,its accumulation begins to decrease.The mean cadmium content of each part of crayfish from high to low ranked as Backshell>Headshell>Hepatopancreas>The muscles.3.Crayfish health risk assessment（1）The maximum EDI values of cadmium,chromium,mercury and lead in the middle and lower reaches of the Yangtze River were 1.21×10-5,1.19×10-4,3.32×-6and 3.52×-5mg/kg*bw/day,respectively,which were far lower than the corresponding PTDI.The THQ values of four heavy metals in Qianjiang,Shishou,Jianli,Shayang,Honghu,Jianhu,Huarong and Huoqiu in different geographical environments are on the order of 10-3-10-5,far less than 1.The hazard index（HI）of adult crayfish exposure was also less than 1,indicating that heavy metal exposure in crayfish in the middle and lower reaches of the Yangtze River did not cause potential non-carcinogenic risk.The cancer risk values of cadmium in crayfish from Qianjiang,Shishou,Jianli,Shayang,Honghu,Jianhu,Huarong and Huoqiu were 2.54×10-5,1.93×10-5,1.25×10-5,8.87×10-6,1.21×10-5,3.77×10-6,1.49×10-5and 7.05×10-6.Cadmium levels in crayfish from these eight regions are within acceptable limits.The other three have little or no cancer risk and are negligible.（2）For chromium,EDI value in circulation was the highest,which was 1.78×10-4mg/kg*bw/day.For cadmium,EDI value of restaurant was the highest,7.16×10-6mg/kg*body weight/day.For lead,EDI value was the highest in culture,2.4×10-5mg/kg*bw/day.For mercury,EDI value of processing stage was the highest,which was 4.14×10-6mg/kg*bw/day.Obviously,at the average exposure level,EDI value of each link is lower than the corresponding PTDI.THQ and HI values of each link were far less than 1,and heavy metal exposure in each link did not lead to potential non-carcinogenic risk.The cancer risk values of cadmium in aquaculture,circulation,processing and restaurant crayfish were1.26×10-5,1.4×10-5,6.46×10-6,1.5×10-5,respectively.Therefore,the potential carcinogenic risk caused by cadmium exposure in crayfish should not be ignored. |
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