Occupational Co-Exposures to Noise and Chemicals—Review of Evidence and Regulatory Perspective

The potential for harmful synergistic effects of workplace noise and chemical exposure is well-established. However, it is less conclusive whether such effects could still be seen if operators were complying with the relevant exposure standards for noise and/or chemicals. Bearing a regulatory perspective, this literature review explored whether any trends in the effects of combined exposure to noise and toxic chemicals could be established. A literature search was undertaken in seven databases, using key search terms on the combined effects of occupational noise and chemical exposures. A total of 1742 articles were identified, among which 82 were assessed in greater detail. Results in animals demonstrated a synergism of styrene, toluene and carbon disulfide when noise is delivered as a repeated ‘impulse’. Other evidence suggested that noise, although at high levels, was responsible for systemic toxicity in organs other than hearing or nerves. Another significant observation was the early signs of hearing loss associated with mixed solvent exposures and noise, each below the respective occupational exposure limits (OELs). Based on these findings, we wondered whether current workplace exposure standards for noise give adequate protection against damage to hearing for workers exposed to chemicals like styrene or toluene. Additionally, they questioned whether compliance with airborne exposure standards and noise levels gave adequate protection for chemicals with a ‘Skin’ notation.