Occupational chronic exposure to organic solvents. X. Biological monitoring parameters for methanol exposure

Twenty persons occupationally exposed to methanol were examined according to their methanol levels in blood and urine and their formic acid excretion. An 8-h exposure to a methanol concentration of 93 ml/m3 (geometric mean) in the air at the working area caused average methanol levels in blood and urine of (8.9 +/- 14.7) mg/l and (21.8 +/- 20.0) mg/l, respectively, and a mean formic acid excretion of (29.9 +/- 28.6) mg/l. These average concentrations for the exposed group showed statistically significant increases compared to those of a control group. For the methanol workers we succeeded in correlating their methanol levels in blood and urine. When considering the possible application of these parameters for biological monitoring, difficulties were encountered, especially for the individual case from the overalapping range in the concentrations of exposed and unexposed persons for each of the applied parameters. This range is minimum for the methanol concentration in urine. About 80% of the urinary levels from the methanol workers lies above the upper limit within the control group range. Based on our results a rough estimate shows the corresponding methanol content in urine to be about 40 mg/l for an 8-h exposure at 200 ml/m3 (German MAK value).