Blood toluene as a biological index of environmental toluene exposure in the "normal" population and in occupationally exposed workers immediately after exposure and 16 hours later.

Blood toluene was measured in a group of 100 workers occupationally exposed to a mean 8-h environmental toluene concentration of 128 mu g/1 (34 ppm), and in a group of 269 ''normal'' subjects without occupational exposure to toluene. The mean blood toluene of the workers at the end of the shift and the following morning, after 16 h, was 457 and 38 mu g/1, respectively, The normal subjects had a blood toluene level of 1.1 mu g/1. On the basis of the highly significant correlation between blood toluene and occupational exposure, it can be calculated that environmental toluene exposure of 188 and 377 mu g/1 (50 and 100 ppm) gives end-of-shift blood toluene levels of 690 and 1390 mu g/1, respectively. The corresponding blood toluene levels on the following morning are 50 and 100 mu g/1, respectively.