A six-year follow up study for evaluation of the 85 dBA safe criterion for noise exposure.

This study included 114 workers who have been exposed to noise levels of 78 to 91.4 dBA and followed over a six year period. Workers exposed to nose levels up to 85 dBA eight hours daily for six days per week and for twelve years showed a slightly higher (1%) hearing impairment than the corresponding control subjects. Impairment of hearing among workers exposed to higher noise levels was 9.6%.