| Environmental air pollution caused by the drift of chemical pesticides during spraying has attracted high attention.Currently,the assessment of human inhalation exposure to pesticide residues is analyzed based on the unit exposure obtained from pesticide residues in environmental air collected by air samplers,leading to uncertainties in the assessment results.Inhalation bioaccessibility can accurately reflect the actual exposure level of pesticide residues in the human body.Therefore,how to apply it to assess inhalation exposure to pesticide residues in spray scenarios has become an urgent scientific issue to be addressed.In this study,the object of investigation was emamectin benzoate.By studying the unit exposure（UE）of the tested pesticide and its influencing factors in the scenario of electrostatic spraying,the inhalation bioaccessibility of the tested pesticide residues in environmental air was determined.The inhalation exposure risk levels to pesticide residues for the applicators and the surrounding population were quantitatively assessed.This provides a theoretical basis for correctly evaluating the inhalation exposure risk of pesticide residues in environmental air,as well as the development of scientifically guided guidelines for the rational use of pesticides.The main research results are as follows:1.Establishment of residue analysis methods for the tested pesticide in simulated lung fluid,rat plasma,and sampling mediaUPLC-MS/MS residue analysis methods for emamectin benzoate were established in simulated lung fluid（Gamble’s Solution[GS],Artificial Lung Fluid[ALF],and Simulated Lung Fluid[SLF]）,rat plasma,and sampling media.The recovery results indicated that at the addition concentrations of 0.01,0.1,and 0.5 mg/L,the recovery rates of the tested pesticide residues in simulated lung fluids（GS,ALF,and SLF）were in the range of84.75-102.12%,with relative standard deviations（RSD）of 3.20-12.38%.At the addition concentrations of 0.05,0.5,and 5 mg/L,the recovery rates of the tested pesticide residues in rat plasma were 83.70-88.67%,with RSDs of 9.00-14.67%.At the addition concentrations of 0.05,0.2,and 1 mg/kg,the recovery rates of the tested pesticide residues in the sampling media were 92.47-102.93%,with RSDs of 5.16-13.62%.The linear relationship within the concentration range of 1-100μg/L was good,with determination coefficients（r2）of 0.9986-0.9998.The limits of detection（LOD）and quantification（LOQ）were 0.001 mg/L and 0.01 mg/L,respectively.2.Study on unit exposure of the tested pesticide and its influencing factors in the scenario of electrostatic sprayingBased on personal air samplers collecting environmental air during the spraying process,the unit exposure of pesticides for applicators in the scenario of electrostatic spraying was measured.The results showed that under the recommended dosage of 3.42 g a.i./ha,the unit exposures of 3%emamectin benzoate emulsion using a fan single nozzle,a fan three-nozzle,and a disc five-hole nozzle were 28.04 ng/m3,10.47 ng/m3,and 14.28 ng/m3,respectively.The unit exposures of 5%emamectin benzoate water dispersible granules using three different nozzles were 29.94 ng/m3,8.50 ng/m3,and 11.05 ng/m3,respectively.Nozzles with smaller volume median diameters（VMD）produced smaller droplet sizes in the sprayed liquid,resulting in higher unit exposures.Based on medium flow air samplers collecting environmental air 50 m downwind from the treated farmland,the unit exposures of pesticides for the surrounding population in the sprayed environment were measured.The results showed that at 2 hours after spraying,the unit exposures of 3%emamectin benzoate emulsion and 5%emamectin benzoate water dispersible granules were in the range of 0.23-0.66 ng/m3and 0.22-0.32 ng/m3,respectively.From 2 to 24 hours after spraying,the unit exposures of the tested pesticide significantly decreased to only 0.001-0.016 ng/m3and 0.003-0.016 ng/m3.When considering a 24-hour inhalation exposure frequency for the surrounding population,the average unit exposures of the two formulations of the tested pesticide were 0.0201-0.0596 ng/m3and0.0238-0.0592 ng/m3,respectively.3.Evaluation of inhalation bioaccessibility of the tested pesticide residueThree in vitro methods were used to simulate parameters for inhalation bioaccessibility,and the effects of factors such as residence time,solid-liquid ratio（S/L）,and oscillation rate on the in vitro measurement of inhalation bioaccessibility of the tested pesticide were studied.The results showed that the inhalation bioaccessibility of the tested pesticide in the three simulated lung fluids（GS,ALF,SLF）increased with increasing residence time and reached equilibrium at 12 hours.The inhalation bioaccessibility showed an initial increase followed by a decrease with increasing S/L,with the highest bioaccessibility observed at an S/L ratio of 1/1000,which was 34.34%,20.09%,and 23.64%for GS,ALF,and SLF,respectively.At an oscillation rate of 200 r/min,the inhalation bioaccessibility was relatively high,with values of 37.05%,39.58%,and 31.08%for GS,ALF,and SLF,respectively.The response surface methodology was used for optimization design,and the maximum inhalation bioaccessibility of the tested pesticide residue was determined to be33.41%.Considering the important parameter of S/L that affects the in vitro lung simulation method for inhalation bioaccessibility,an in vivo-in vitro correlation（IVIVC）analysis was conducted by comparing the inhalation bioavailability data of the tested pesticide obtained from animal（rat）experiments with its data at different S/L ratios（using GS as the simulated lung fluid）.It was found that the IVIVC model showed good correlation（r2=0.6313）when the S/L ratio was 1/1250.Therefore,the parameters for the in vitro lung simulation method for the tested pesticide residue were determined as follows:extraction time of 24 hours,oscillation rate of 200 r/min,and S/L ratio of 1/1250.Under these conditions,the inhalation bioaccessibility of the tested pesticide residue was 32.33%.4.Inhalation exposure assessment of the tested pesticide based on inhalation bioaccessibility evaluationBased on the unit exposure of the tested pesticide in the scenario of electrostatic spraying,combined with the inhalation bioaccessibility of the tested pesticide,the inhalation exposure assessment was conducted for applicators and the surrounding population in the sprayed environment（50 m downwind）.The results showed that at the recommended dosage,the average daily dose（ADD）of inhalation exposure to the tested pesticide residue for applicators and the surrounding population ranged from 2.12×10-6to7.46×10-6mg/kg·day and from 5.01×10-9to 1.49×10-8mg/kg·day,respectively.The margin of exposure（MOE）for the tested pesticide residue based on inhalation bioaccessibility ranged from 2.59×104to 8.53×104and from 9.98×104to 1.78×105for applicators and the surrounding population,respectively,which were all within an acceptable range（>100）.Among them,the exposure risk was relatively higher when using a fan single nozzle to spray the 3%emamectin benzoate emulsion.If the important factor of inhalation bioaccessibility is not considered,the MOE of the tested pesticide would be overestimated by 50-68%. |
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