Average cochleogram obtained from rats exposed to [OBN: 8kHz; 86.2 dB SPL]; yellow bar corresponds to hair cell loss at 400 ppm; dark bar to noise and styrene exposure (respectively OBN: 8kHz; 86.2 dB SPL + 400ppm). Exposure schedule: 6h/d, 5d/w, 4w. Abscissa - upper trace: length (mm) of the spiral course of the organ of Corti.-lower trace :frequency-map. Ordinate: hair cell loss in percent. IHC: inner hair cells; OHC1: first row of outer hair cells; OHC2: second row; OHC3: Third row.