Evaluation of biological monitoring parameters for occupational exposure to toluene

A survey was conducted in a rotogravure printing plant with inhalatory and percutaneous exposure to toluene. Workers (n=9) were followed for 2 consecutive days and the frequency and duration of skin contact with toluene were monitored. In order to assess percutaneous absorption an airstream helmet was worn during one day. Urine and exhaled air samples were collected simultaneously 5 times each day for toluene (urine and breath) and hippuric acid (urine). The mean (personal air sampling) exposure concentration was between 30 mg/m³ and 600mg/m³. The best biological monitoring parameter of external exposure (without a helmet) was the concentration toluene in exhaled air 8 h after work (r-0.99). While wearing the airstream helmet the relationship between external exposure (measured in the helmet) and concentrations in exhaled air and urine deviated from the preceding relations. This was likely the result of the high body burden and not of skin contact with toluene. Skin contact with toluene (usually by cleaning of the hands) was limited to 0-30 minutes a day, with an average of about 5 minutes. During experimental exposure (n=6) in which the hands were washed with toluene for 5 minutes the toluene in exhaled air (max after 1040 min) clearly demonstrated skin absorption of toluene. The next morning 0.1 mg/m³ toluene was still detectable; this was less than the concentration measured the next morning in exhaled air of workers: between 0.5 and 10mg/m³.