Pollution Source And Risk Assessment Of Phthalate Esters In Tea

Phthalate esters?PAEs?,a group of diesters of ortho-phthalic acid,are important environmental endocrine disruptors.Toxicological studies on PAEs have indicated their adverse effects on health,including teratogenesis,carcinogenesis and mutagenesis,which cause high attention of consumers.As a result,PAEs have been classified as priority pollutants by many countries.Our previous study conformed that the residue levels of 16 PAEs in tea samples ranged from 305.0?g/kg to 1210.0?g/kg with a detection rate of 100%.However,information on the occurrence and residue pattern of PAEs in either fresh tea leaves or during tea processing is still lacked,as well as that on relative risk assessment.Thus it is essential to explore the source of PAEs during tea planting and processing,and to perform the risk assessment.This study provided preliminary data for risk control and assessment of PAEs in tea planting and processing,and supplyed information for the establishment of a maximum residue limit?MRLs?for PAEs.In this study,PAEs sources in tea from different aspects,including plantation,processing and packaging,were studied.The presence of 16 PAEs in fresh tea leaves as well as made tea and the residue pattern of PAEs during tea manufacturing were investigated firstly.The influence of packaging and storage conditions for PAE levels in tea were then studied.Finally,the isotope technique was applied to assess the transfer rates of 7 PAEs during tea brewing in order to avoid the background interferential,and the preliminary risk assessment was also conducted.The main content of this project is as follows:?1?The PAE concentrations in fresh tea leaves with different maturity,which were collected from mountainous and highway regions,was investigated.The effect of highway-source pollutants to the PAE contents in different tea plant organs was studied.The discrepancy of PAE residue levels in tea leaves?consisting of one bud and two leaves?and made tea from different district was analysised.Eight PAEs were found in all tea samples.The amount of?₈PAEs distribution was as follows:lower mature leaves>upper mature leaves>three and four leaves>one and two leaves>bud;the amounts of DMP,DiBP,DEHP,DMEP,DPrP,and DNP obviously increased as the fresh leaves matured,while DMEP,DNP and DPrP were only detected in mature leaves.DBP and DEP,detected in all five groups,had relatively low concentrations in the samples and showed no significant correlation with the maturing degree of the leaves.Besides,the concentration of?₈PAEs in fresh tea leaves of shoots picked from highway regions was slightly higher than that picked in mountainous regions,and the highway-source PAEs had little influence to the PAE concentrations in upper mature leaves,lower mature leaves and tender stem except for one bud and two leaves within a range of 100 m.There is a little difference of total PAE contents in tender fresh tea leaves at West Lake District and Songyang County,while the difference among the various kinds of PAEs were large.Similarly,there was no significant difference in total PAE contents between Longjing tea of 3 different regions and 4 breeds in Zhejiang province.?2?One bud and two leaves obtained from the two sampling sites were subjected to traditional green tea processing,and the residue levels and transformation pattern of PAEs in tea sample of different stages was studied.The total loss of?₅PAEs was 61%⁶3%during baked green tea manufacturing.Among all manufacturing steps,drying contributed to the largest loss of PAEs which accounting for 61.3%⁷3.7%of the total degration rate followed by spreading and fixing.The contents of the other 4 PAEs decreased after tea processing except for DEHP?increased by 10%²2%?.?3?The influence of packing and storage conditions on PAE contents in tea was investigated.The total PAEs translocation from plastic packages to made tea was low at both room temperature?14²7^oC?and 4^oC in three months.According to our experiment,the correlation of PAE concentrations in green tea and packaging materials were not significant except for the situations when paper bags or tea bags were involved.?4?The tansfer rates of PAEs from made tea to tea infusion were studied using the isotope technique because of PAEs background pollution problem.The transfer rates of 7 PAEs from made tea to infusion were 5.2%¹00.6%,which was positively correlated to water solubility and negatively correlated to Log Kow of corresponding PAEs;The transfer rates of PAEs with a relatively low Ws?below 1 mg/L,25^oC?and a high Log Kow?higher than 5?were similar during the first and second brewing.Otherwise,the transfer rates decreased greatly with prolonged brewing;furthermore,transfer rates were also affected by tea kinds and tea/water ratio,and have not significant correlation to the spiked levels of PAEs.Risk assessment study indicated a low health risk of PAEs intake by drinking tea.