OCCUPATIONAL CHRONIC EXPOSURE TO ORGANIC-SOLVENTS .6. FORMIC-ACID CONCENTRATION IN BLOOD AND URINE AS AN INDICATOR OF METHANOL EXPOSURE

A study was carried out among 20 workers employed in a printing, office at three different work places (methanol concentration: 85, 101, and 134 ppm) to determine whether the concentration of formic acid in blood or urine and the methanol content of alveolar air permit the estimation of methanol exposure. For this purpose blood, urine, and end expiratory air were collected at the beginning and the end of the shift. For comparison formic acid concentrations were determined in the morning and in the afternoon in blood and urine of 36 and 15 control persons, respectively. The concentration of formic acid in blood increased significantly from 3.2 ± 2.4 mg/l before to 7.9 ± 3.2 mg/l after the shift in the exposed workers (mean increase 4.7 ± 3.8 mg/l). The corresponding concentrations in urine were 13.1 ± 3.9 mg/l and 20.2 ± 7 mg/l, respectively, with a mean increase of 7.1 ± 5.3 mg/l. This difference is also significant. On the contrary, in the control groups there was a small but significant decrease of formic acid concentration in blood from 5.6 ±4.5 mg/l in the morning to 4.9 ± 4.2 mg/l in the afternoon. In urine, the formic acid concentrations in the morning (11.9 ± 6.4 mg/l) and in the afternoon (11.7 ±5.6 mg/l) were not significantly different. The increase of formic acid concentration in blood during the shift is the most useful parameter for monitoring methanol exposed persons. In contrast determinations of methanol concentrations in the ambient air or in the exhaled air are only crude estimates. © 1979 Springer-Verlag.