| Pesticide is an indispensable material in agricultural production.It is useful to our human beings,but it also brings some negative impact.Currently,There are some prejudices and fallacies to recognize the toxicity of pesticide.When we have a fight sight of pesticide and its relationship with human health,we can reasonably use pesticide to promote the development of agriculture.Drinking tea is good for human health,but more and more attention has been paid to the question whether the trace pesticide residue in tea is harmful to the drinker.A lot of countries have established many standards of MRLs in tea in order to protect the health of people.But there is a big difference of MRLs between various governments,districts and international organization,which confuses the tea farmers to choose pesticide,brings some doubts to the consumer and causes handicap to the international tea trade.The theory and technology of human health risk assessment from harmful substances in food is a new discipline developed from 1980s,which is applied popularly in developed countries such as the USA.International organization like FAO,WHO promulgated related guidelines to suggest its members to apply them in food safety field.Recently,our country have gradually pay attention to the value and importance of risk assessment,but the application and research in detail are not systematically carried out.China is a large country in tea production and export in the world.In this paper,we carried out the risk assessment research from the pesticide residue in tea,estimated the risk level that pesticide residue in tea to human health and evaluated the MRLs of pesticide in tea.The results will provide the scientific evidence for establishing reasonable pesticide residue standard of tea and the technological support for breaking the technological trade barricade in international tea trade,which have important academic and realistic significance to guide the produce of tea and promote the consumption of tea.The main research results were as following:1.We collected more than 800 standards of pesticide MRLs in tea established by 17 countries and international organizations,and analyzed the characters of pesticide MRLs in tea established by EU and Japan.MRLs of EU is dynamic because the items of pesticide standards increased nearly three multiples from 43 of 1993 to 172 of 2004.and MRLs standards of EU are very low,93%of the total items are the limits of detection,which are far lower than the standards of CAC.The number of MRLs in Japan is the largest.There are 276 items MRLs of pesticide in "positive list system".Comparing the MRLs established by various countries,districts and international organizations,there is a huge difference.Some items differ from each other 10 multiples,even 100 multiples.It indicates that the establishment of pesticide MRLs in tea lacks the foundation of risk assessment in each country or international organization.2.We carried out the exposure assessment of drinking tea.We chose some representative cities in tea consumption,conducted a questionnaire survey with the "three days dietary retrospect" method.The results indicated that the highest amounts of tea consumption per person per day is 45 g,the lowest is 3 g,the average is 11.4 g.The individual consumption amount of tea per kilogram per day is an important datum in the risk assessment of pesticide residue in tea.During the group of drinking tea,the highest amount of consumption per kilogram per day is 0.64 g/kg.bw,the lowest is 0.048g/kg. bw,and the average is 0.1738 g/kg.bw.In this investigation,we computed the consumption amount of tea per day per kilogram according to the individual actual weight.The result will provide the basic data for exposure assessment of pesticide residue in drinking tea.3.The extracting rule of pesticide residue in made tea during brewing process is studied.Three selected pesticides(fenvalerate,endosulfan and triazophos)were sprayed in tea gardens at two doses.The green shoots were harvested from treated plot at 2 hours and 1,2,3,5,7,9,14,21days after the treatment and manufactured into green tea.The concentrations of the selected pesticides in made tea,tea infusion and infused leaves were determined by GC.The results indicated that the residues of selected pesticides in made tea and tea infusion decreased gradually while the plucking interval increased.The concentration of pesticide in tea infusion(y)show quadratic function with that in made tea(x).Quadratic equations of fenvalevate-trans,fenvalevate-cis,endosulfan and triazophos are y=-0.0006x2+0.0229x(R2=0.971),y=-0.0001x2+0.00944x(R2=0.938) and y=0.00016x2+0.0069x(R2=0.977),y=0.003x2+0.4503x(R2=0.982),respectively.The extracting rate of pesticide in made tea during brewing process mainly depends on the solubility of pesticide.The solubility of Triazophos is relative high,the extracting rate of which is higher in tea infusion;The solubility of Fenvalerate and endosulfan are relative low,the extracting rates of which are correspondingly lower.The insoluble pesticide mainly remained in infused leaves.4.Human health risk assessment from pesticide residue in tea was studied by four steps:hazard identification,dose-response assessment,exposure assessment and risk characterization.The hazard identification and dose-response assessment of three selected pesticides(fenvalerate,endosulfan and triazophos)were studied according to the JMPR toxicology data.The residue data of fenvalerate,endosulfan and triazophos were collected from 831 tea samples in consumption area,and the distribution of selected pesticide residues in tea was studied and the modeled curves were established.The actual intake amounts of selected three pesticides were obtained by Monte-Carlo Method.The probability distribution curves of selected pesticides exposures indicate:the exposure doses per day of fenvalerate in percentile of 50%,90%and 99%of the drinking tea group are 0.8×10-7mg/kg bw,2.18×10-7mg/kg bw and 5.47×10-7mg/kg bw,respectively,which are not high than 0.0004%,0.00109%and 0.00274%of the ADIs respectively;The exposure doses per day of endosulfan in percentile of 50%,90%and 99%of the drinking tea group are 0.5×10-8mg/kg bw,1.42×10-8mg/kg bw and 3.23×10-8mg/kg bw,respectively, which are not high than 0.000083%,0.000236%and 0.000538%of the ADIs respectively; the exposure doses per day of triazophos in percentile of 50%,90%and 99%of the drinking tea group are 3.34×10-7mg/kg bw,6.80×10-7mg/kg bw and 1.33×10-6mg/kg bw,respectively,which are not high than 0.0334%,0.068%and 0.133%of the ADIs respectively.It can concluded that the pesticide exposure dose of drinking tea is very lower, and its percentage of the ADI is also very lower.5.The pesticide MRLs in tea were evaluated.We respectively calculated the safety coefficients of three selected pesticides corresponding with their MRLs.The safety coefficients of fenvalerate,endosulfan and triazophos were 71000,21 and 2500, respectively corresponding with fenvalerate MRL of EU,endosulfan of CAC,EU and Japan,triazophos MRL of EU.The large differences of the safety coefficients show that various countries and international organizations demand a scientific and reasonable guideline.In this paper,the uncertainty of the risk assessment in this research was discussed and demonstrated. |
PDF Full Text Request