Urinary hippuric acid and orthocresol excretion in man during experimental exposure to toluene.
It is not known whether urinary excretion of hippuric acid (HA) or orthocresol (O-Cr) is to be preferred for the biological monitoring of workers with occupational exposure to toluene. To study this, 42 printing trade workers with more than 10 years' exposure to a mixture of organic solvents including toluene (0-20 ppm) and 43 control subjects matched by age, smoking habits, and living accommodation were investigated. Each matched pair was randomised to an experimental exposure of either 100 ppm or 0 ppm toluene for 6.5 hours under controlled conditions in an exposure chamber. Urinary excretion of HA and O-Cr was determined by high pressure liquid chromatography from samples obtained before exposure, during the first three hours, and during the last 3.5 hours of exposure. No difference in HA and O-Cr excretion was found between printing trade workers and controls. The median O-Cr excretion increased 29 times during exposure, whereas the HA excretion increased only five times. Thus only 3% of the O-Cr excretion originated from other sources than toluene whereas the corresponding value for HA was 19%. Standardisation of the concentrations of HA and O-Cr in relation to urinary creatinine reduced the relative variation by 29% and 56% respectively. This was not reduced further by expressing the excretions as average excretion rates based on total volume of urine collected. Background urinary O-Cr excretion was three to four times higher among smokers than non-smokers, probably due to the content of O-Cr in cigarettes. The O-Cr excretion in unexposed smokers was, however, 10 times lower that that of the non-smokers during the end of the experimental exposure to 100 ppm toluene.
D000328:Adult; D002851:Chromatography, High Pressure Liquid; D003408:Cresols / Q000652:urine*; D004781:Environmental Exposure; D006626:Hippurates / Q000652:urine*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009787:Occupational Medicine; D011327:Printing; D012907:Smoking; D014050:Toluene / Q000378:metabolism* / Q000506:poisoning
D003408:Cresols; D006626:Hippurates; D014050:Toluene; C030514:hippuric acid; C034047:2-cresol