Studies On The Revision Of The Biological Limit Value Of Occupational Exposure To Fluorine And Fluorides

Objective：To revise the biological limit value of occupational exposure to fluorine and fluoridesfor actually reflecting accurate exposure of workers in china.Method：In early2004China had recommended the National Standard Method for determinationof fluorides in the air of workplace for fluorides in the air.The sanitary standard, Determinationof Urine Fluorine by Ion Selected Electrodes,was chosen for measuring the urine fluorideconcentration of occupationally exposed workers.141subjects working more than5years froman aluminiun factory in HUBEI province were selected, whom came from institution,aluminumpole workshop and potroom. The correlation of urinary fluoride levels and the concentrations offluorides in the air of workplace was found out,and established linear regression equationthrough occupational epidemiological investigation in field.In2004China the biologicalexposure limit values for fluorine and fiuorides in urine were estimated as4mg/gCr (6.8mg/L)atthe prior to shift and7mg/gCr(11.9mg/L)at the end of shift.Based on abroad documents anddata, we explored the feasibility of the biological limit value through field investigations in thisstudy, in order to revise the biological limit value of occupational exposure to fluorine andfluorides.Results：The fluoride content of occupational exposure workers was detected with fluorideselective electrode.In urine,this methods showed good linear relationship in the range of0.1mg/L~1.0mg/L. The detection limit of method for fluoride in urine was0.05mg/L, the lowestdetected concentration was0.1mg/L,the relative standard deviation(RSD) was3.96%～6.02%,and the rate of recovery is within96.40%~104.2%; In the air of workplace, this methodsshowed good linear relationship in the range of1μg~100μg. The detection limit of method forfluoride was1μg, the lowest detected concentration was0.01mg/m3,the relative standarddeviation(RSD) was2.89%～7.44%,and the rate of recovery is within96.40%~105.6%.According to the study, there existed a good dose-response(effect) relation between thecorrelation of urinary fluoride levels and the concentrations of fiuoride in the air. the linearregression equation were (Prior to shift) Y(mg/L)=1.2017x(mg/m3)+0.5059,（r=0.91,n=100,p<0.05）, and(End of shift) Y（mg/L）=2.1122x(mg/m3)+0.5971（r=0.96，n=100，p<0.05）.Comepared with the linear regression equation between the study and liberature review, the equivalenturinary values were2.91mg/L (Prior to shift) and4.82mg/L (End of shift), withone exposure to2.0mg/m3of F-.Conclusion：The detection method by fluoride ion selective electrode was rapid,accurate,simple.and no dealing with the urinary samples.After revision of the biological limit value ofoccupational exposure to fluorine and fluorides, the relative internal exposure index (RIE) offluoride in urine of China are1.5at the prior to shift and2.5at the end of shift, it is namely thatthe excretion of fluoride via urine are1.5mg/L(prior to shift) and2.5mg/L (end of shift),whenthe inhaled fluoride is1mg/m3. According to Occupational exposure limits for fluorine andfluorides in the workplace of fluoride (PC-TWA=2.0mg/m3)in China,consulting the biologicalexposure limit value to fluorine and fluorides,and RIE values of other countries,combining withthe relevant aboard documents, data and this study result, the biological exposure limit values forfluoride in urine in China were revised as3mg/L at the prior to shift and5mg/L at the end ofshift.