Uptake And Subcellular Distribution Of Triclosan In Aquatic Plants

Triclosan,one of Pharmaceuticals and Personal Care Products（PPCPs）,has been widely used in daily life and frequently detected in environment.The increasing discharge of Triclosan into the environment has generated serious public concern.The recent awareness of the environmental impact of this emerging class of pollutants and their potential adverse effects on human health have been documented in many reports.However,information regarding uptake and intracellular distribution of PPCPs in hydrophytes under hydroponic conditions,and potential human exposure is very limited.¹⁴C labeled triclosan was employed in this study,combining with radionuclide tracing technique,radioautographic technique and differential centrifugation technique,to investigate the uptake and distribution of ¹⁴C-TCS in cress,water spinach,penny grass,cane shoot,purple perilla and rice in both competitive and non-competitive hydroponic system.As well,the subcellular distribution of ¹⁴C-TCS was explored by using the differential centrifugation technique.Meanwhile,the risk to human health by eating cress,water spinach and purple perilla was also estimated by the annual vegetable intake of per Chinese person.The study could provide a scientific basis for the knowledge of triclosan environmental behavior and safety,and technical reference for the relevant researches of PPCPs,as well as basic data for food safety evaluation of aquatic vegetables in contaminated areas in China.The results showed as follows:1)in competitive system,good mass conservation of ¹⁴C-TCS was observed for the tested plants（95.33%-103.60%）.The bioconcentration factor（BCF）of ¹⁴C-TCS in cress（244.6 ml/g）was the highest in the six aquatic plants,followed by water spinach>cane shoot>rice>penny grass>purple perilla.The percentage content and concentrations of ¹⁴C-TCS in plant roots were 2-3 orders of magnitude greater than its concentration in shoots,among which the concentration of ’4C-TCS in cress（198.66-569.25 μg/g）and water spinach（222.15-564.54 jig/g）roots was significantly higher（P<0.05）than that in other plants,which following the order of penny grass>purple perilla>rice>cane shoot.2)In each non-competitive system,the mass balance of ¹⁴C-TCS was also very good（95.1%-101.4%）.The uptake of triclosan from nutrition solution was 94%and 96%by cress and water spinach in 192 h,respectively,while the uptake amounts of triclosan in other plants ranged from 63%to 87%,indicating that cress and water spinach could be potentially used in phytoremediation of TCS-contaminated water.The ¹⁴C-TCS BCF of cress（438.79 ml/g in 192 h）was the highest in the six aquatic plants,followed by water spinach>cane shoot>penny grass>rice>purple perilla.As the result of the competitive system,the percentage content and concentrations of ¹⁴C-TCS in plant roots were also much higher than that in shoots,about 2-3 orders of magnitude greater than in shoots,which demonstrated that ¹⁴C-TCS was mainly concentrated in plant roots after being absorbed.The result of the radioautography visually confirmed that ¹⁴C-TCS was mainly concentrated in plant roots.The results of human exposure showed that the highest human exposure of 2,4-dichlorophenol（one of the most toxicity metabolites of triclosan）by eating cress,water spinach and purple perilla was 47.35 ng/day/kg,which was also lower than the safe dose of 2,4-dichlorophenol（300μg/day/kg）,suggesting that eating these plants would pose less adverse harm to human health under current experiment conditions.3)The ¹⁴C-TCS subcellular distribution results showed that the percentage content,concentration and SFCF of ¹⁴C-TCS in cell organelles were significantly higher than these in cell walls and cytoplasm,which meant organelles are the main storage site of ¹⁴C-TCS.This study can offer basic data for the study of distribution,translocation and accumulation of triclosan in plants,and provide technical reference for the relevant study of other PPCPs.