Exposure Levels And Environmental Sources Of Per-and Polyfluoroalkyl Substances In Crayfish

Backgrounds:Per-and polyfluorinated substances(PFASs)are a group of persistent organic pollutants.Their prolonged use and widespread application have led to their widespread presence in the environment and their accumulation in living organisms through the food chain.PFASs are non-lipophilic,structurally similar to natural fatty acids and are not readily enriched in fat when they enter organisms,but rather attach to proteins in the blood and liver,so that plasma proteins in the body combine with most of the PFASs that enter and remain in the blood,with the remainder accumulating in the animal’s liver and muscle tissue.Studies have shown that human exposure to PFASs can have adverse effects on the immune system,endocrine system,metabolism and reproductive system and increase the risk of cancer.Humans are exposed to PFASs through multiple pathways,primarily through diet,with aquatic products being considered the main route of dietary exposure in humans.According to the China Crayfish Industry Development Report(2020),the total output value of China’s crayfish industry in 2019 was up to 411 billion RMB,which is an important aquatic product in China’s Yangtze River basin.This study detects and analyses the exposure levels of PFASs in crayfish from the main crayfish production and consumption regions in China,and analyses and studies their main sources.Methods:(1)Samples of crayfish from representative cities were selected for collection,and the content of PFASs in crayfish was examined by LC-MS/MS,followed by comparative analysis of PFASs in crayfish from different distribution stages.(2)The levels of PFASs in different parts of the collected farmed shrimps(muscle,dorsal shell,cephalic shell and hepatopancreas)and the environment in which they grow(water and sludge)were detected and subjected to Spearman correlation analysis.(3)Crayfish were exposed to different doses of PFBA(25,250 and 2500 ng/L),PFOA(10,100 and 1000 ng/L),PFBS(5,50 and 500 ng/L)and PFOS(2,20 and 200 ng/L)in the water for 14 days and the levels of PFCs in crayfish muscle,dorsal,cephalic and hepatopancreas as well as in the whole shrimp were examined.Results:(1)The detection rate of PFASs in 130 crayfish samples was 100%,and there were ten target compounds detected,all with a detection rate greater than 50%.The concentrations of ∑PFASs ranged from 0.195-2.796 ng/g,with a mean concentration of1.435 ng/g.The trend in mean concentrations of ∑PFASs in crayfish samples from different distribution stages was: farmed shrimp(1.724 ng/g)> market shrimp(1.677ng/g)> restaurant shrimp(1.410 ng/g)> semi-processed shrimp(1.229 ng/g)> processed shrimp(1.042 ng/g).(2)The mean concentration levels of ∑PFASs in different parts of cultured crayfish trended as follows: hepatopancreas(7.485 ng/g)> cephalic shell(1.938 ng/g)> dorsal shell(1.237 ng/g)> muscle(0.597 ng/g).Eleven target compounds were detected in the water,with concentrations of ∑PFASs ranging from 18.871 to 176.010 ng/L,with a mean concentration of 49.059 ng/L.Seven target compounds were detected in the sludge,with concentrations of ∑PFASs ranging from 0.106-0.407 ng/g and a mean concentration of0.246 ng/g.The mean concentrations of ∑PFASs in the crayfish,water and sludge from the Jianhu were the highest,indicating that Jianhu is more heavily contaminated by PFASs.The correlation results showed that PFBA,PFOA,PFBS,PFOS and water had significant positive correlations(p<0.05)in all samples except for PFBA in shrimp,PFBS in muscle,PFOS in head shell and hepatopancreas.(3)After 14 days of exposure of crayfish to different doses of PFBA,PFOA,PFBS and PFOS through the water,the overall trend in the distribution of the different compounds in different parts of the crayfish was: hepatopancreas > cephalic shell > dorsal shell > muscle.which was consistent with the distribution trend in the collected farmed shrimps,indicating that the target compounds were first enriched in the liver after entering the crayfish.