“…This conclusion is consistent with a report that "active" rats inhaling 300, 400, 500, or 600 ppm styrene (6 h/day, 5 days/week for 4 weeks) exhibited no changes in auditory permanent threshold shifts (PTS; measured over 2-32 kHz) at 300 ppm despite an average 5% loss in third-row OHCs, or in "sedentary" rats exposed to 500 ppm with a corresponding 3% OHC loss (Lataye et al 2005). Similarly, for the equi-ototoxic styrene analog ethylbenzene, exposure of rats to 200 ppm ethylbenzene (6 hours/day, 6 days/week for 13 weeks) resulted in an average 4% third-row OHC loss, with no corresponding changes in audiometric thresholds at 2, 4, 8, and 16 kHz evaluated at 4, 8, 13, and 21 weeks after exposure initiation (Gagnaire et al 2007). It therefore seems reasonable to consider 200 mg/kg bw/day for 24 weeks as an oral NOAEL for functional hearing loss.…”