2.3 Indicators of Hearing Damage 55 exposed to the OSHA-permitted levels over their lifetime will experience some hearing loss. Remember that each of these recommendations assumes that one is accounting for all of the noise exposure for the day. Someone who works in a noisy environment, and then goes home and uses power tools or lawn equipment is further increasing their risk and exposure. The U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO) have recommended a 75 dB limit, as shown in Table 2.3, as a safe exposure with minimal risk of hearing loss. The WHO goes on to recommend that exposure such as encountered at a rock concert be limited to four times per year. 2.3 indicAToRS oF HeARing dAMAge There are several indicators of hearing damage. Since the dam- age is both often slow to manifest itself and progressive, the most