Drawbacks of occupational noise exposure limits with exchange rate of 5 dB(A)

Occupational noise, particularly in noisy industrial plants is a potentially serious health problem. Therefore, to ensure the health and safety of the workers against high level occupational noise, occupational noise exposure limits of (i) 90 dB(A) L Aeq , with an exchange rate of 3 dB(A), per halving or doubling exposure time, (ii) 90 dB(A) L Aeq , with an exchange rate of 5 dB(A), (iii) 85 dB(A) L Aeq , with exchange rate of 3 dB(A) or (iv) 85 dB(A) L Aeq , with exchange rate of 5 dB(A) have been set up for industrial plants with a working schedule of 8 h/day and 5 days a week (i.e., 40 h/week), by various countries [1]. The International Institute of Noise Control Engineering, USA [1], has recommended a limit of 85 dB(A) L Aeq , with an exchange rate of 3 dB(A) per doubling or halving exposure time, normalized to 8 hours per day and 40 hours a week. The permissible exposure time per day, for the limits of 85 and 90 dB(A) L Aeq , both with exchange rate of 3 and 5 dB(A), analyzed for each dB(A) values is given in Table 1 (on following page). The approximate values of exposure time for intermediate dB(A) values for the limits of 85 and 90 dB(A) L Aeq , with exchange rate of 3 dB(A) are obtained by multiplying the exposure time of 8, 4, 2, — , — , — h/day with 0.75 and d0.625 [2]. Similarly, for these two limits, with exchange rate of 5 dB(A), the approximate values of exposure time for the intermediate dB(A) values are obtained by multiplying the exposure time of 8, 4, 2, — , — , — h/day, with