The toluene SMACs for exposure durations of 1 h to 180 d (Table 17-1) were set in 1996 based on the lack of neurotoxicity (eight tests measuring 20 parameters) and the lack of irritation of the eyes and nose reported in 16 subjects exposed for 6 h to toluene vapors at 40 . During the same experiment, exposures of 100 ppm resulted in reports of headache, dizziness, and a feeling of intoxication significantly more often than when exposed to clean air (Andersen et al. 1983). Acceptable concentrations (ACs) for neurotoxicity (headache, dizziness, and a feeling of inebriation) were calculated as follows:
The ACs for 7, 30, and 180 d were based on the 40-ppm no-observed-adverse-effect level (NOAEL), using the factor (√n)/10 to adjust for the small number (n) of subjects.
In setting ACs for 1- and 24-h exposures, mild effects such as headaches, irritation, and not-quite-significant decrements in psychometric tests would be acceptable for short-term contingency exposures, but dizziness would not be acceptable, even for brief exposures during contingency operations. Thus, the ACs for 1 and 24 h were also based on the 40-ppm NOAEL, adjusting for the number of subjects.
A NOAEL of 40 ppm of toluene vapor was reported for irritation of the eyes and nose during a 6-h exposure was reported in the same study in 16 young male volunteers. Because irritation depends on concentration but not on exposure duration, the ACs for all exposure durations from 7 to 180 d were based on the 40-ppm NOAEL, adjusting for the small number of subjects by a factor equal to 1/10th the square root of the number of subjects tested.
Some irritation is acceptable for short-term SMACs; therefore, the irritancy ACs for 1 and 24 h were set equal to the 100-ppm lowest-observed-adverse-effect level (LOAEL).