90db is way too high for any extended period of time. Ontario's green book calls for hearing protection at 85db(also too high). Many areas have legislated limits of 80db before protection is required. With the decibel scale being logarithmic, 90db is 10x "louder" than 80db.
I don't know that there is a huge concern if you have already lost the ability to hear those frequencies (the high frequencies tend to go first from environmental hearing damage) or never had the ability. Perhaps it could still cause or aggregate other hearing damage related issues such as tinnitus.
Adam
Barrie,On
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