Abstract

The risk of hearing loss from exposure to ototoxic chemicals is not reflected in occupational exposure limits and most jurisdictions. The aims of this research were to investigate dose-response relationships between exposure to lead, mercury, toluene, and styrene and hearing impairment based on current epidemiological evidence, conduct cross-jurisdictional comparisons, and investigate control measures for exposure to ototoxic chemicals. Ovid Medline and Ovid Embase databases were used to find relevant publications. A total of 86 epidemiological studies met the eligibility criteria for final evaluation. When significant associations between exposure and outcome were identified, exposure levels were evaluated to determine whether No Observed Adverse Effect Level (NOAEL) and Lowest Observed Adverse Effect Level (LOAEL) could be identified. Cross-jurisdictional comparisons included the U.K., U.S., Canada, and Australia occupational health and safety legislations. The majority of lead (75%), styrene (74%), and toluene (77%) studies showed significantly increased risks of hearing loss from exposure to these substances, although numerous studies on toluene (70%) and styrene (16%) compared auditory function between “solvent mixture” or “noise and solvent mixture” exposed groups and controls and not necessarily on groups exposed to a single agent. Based on five studies, blood lead ranges of 1–1.99 μg/dL to 2.148–2.822 μg/dL were identified as NOAELs while blood lead levels of 2 μg/dL up to 2.823–26.507 μg/dL were identified as LOAELs for hearing loss. Except for general duty clauses, the U.S., Canadian, and Australian jurisdictions have set no enforceable regulations specific to ototoxic chemical exposures. A biological exposure index of 2 μg/dL is recommended for prevention of hearing impairment from lead exposure. Based on Safe Work Australia, noise exposure limits may be reduced to 80 dB(A) for 8 hr. Other recommendations include performing audiometric testing and controlling exposure through all routes of entry.

摘要

职业接触限值和大多数管辖区并未反映出因接触耳毒性化学物质而导致听力丧失的风险。这项研究的目的是根据当前流行病学证据研究铅，汞，甲苯和苯乙烯与听力障碍之间的剂量反应关系，进行跨辖区比较，并研究耳毒性化学物质的控制措施。Ovid Medline和Ovid Embase数据库用于查找相关出版物。共有86项流行病学研究符合最终评估的入选标准。当确定暴露与结果之间存在显着关联时，评估暴露水平以确定是否可以确定未观察到的不良反应水平（NOAEL）和最低观察到的不良反应水平（LOAEL）。跨辖区的比较包括英国，美国，加拿大和澳大利亚的职业健康和安全法规。多数铅（75％），苯乙烯（74％）和甲苯（77％）研究表明，接触这些物质可导致听力下降的风险显着增加，尽管有关甲苯（70％）和苯乙烯（16％）的大量研究比较了“溶剂混合物”或“噪音和溶剂混合物”暴露组与对照组之间的听觉功能，而未必是暴露于单一药剂的组之间的听觉功能。根据五项研究，将血铅范围从1–1.99μg/ dL到2.148–2.822μg/ dL的识别为NOAEL，而血铅水平从2μg/ dL到2.823–26.507μg/ dL的识别为LOAEL。 。除一般责任条款外，美国，加拿大，澳大利亚司法管辖区未针对耳毒性化学暴露制定专门的强制性法规。为了防止铅暴露引起的听力障碍，建议将生物暴露指数设为2μg/ dL。根据澳大利亚安全工作组织的规定，可以将噪音暴露限制降低到80 dB（A），持续8小时。其他建议包括执行听力测试和控制所有进入途径的暴露。