Biological monitoring of persons exposed to methanol vapours

Five volunteers were exposed to constant and suitably graded concentrations of methanol vapours for a period of 8 h. The retention of methanol in the lungs and the course of its excretion in urine were monitored at single and at daily repeated exposures. From the concentration in inspired air, lung retention, minute lung ventilation and duration of exposure, the methanol dose retained in the organism of the experimental subjects was calculated. The dose correlated well with the methanol concentration (mmol/l or mg/l) in whole-shift urine; using other units (mg/l corr., mg/creat., mg/time) the correlation was unsatisfactory. An exposure test was proposed which permits the estimation of the retained methanol dose on the basis of an analysis of whole-shift urine. The test yields good results even if the subjects perform physical work and consequently have enhanced lung ventilation, or in cases where the air besides methanol contains vapours of other organic solvents (ethanol, acetone). The results may be burdened by a certain error if the methanol concentration in air fluctuates extremely, or if exposure is interrupted by breaks. Nonetheless even in such circumstances the test provides valuable information on the level of occupational exposure to methanol.