Occupational exposure limits for manufactured nanomaterials, a systematic review

<b>Background:</b> The toxicological properties of manufactured nanomaterials (MNMs) can be different from their bulk-material and uncertainty remains about the adverse health effects they may have on humans. Proposals for OELs have been put forward which can be useful for risk management and workers’ protection. We performed a systematic review of proposals for OELs for MNMs to better understand the extent of such proposals, as well as their derivation methods. <b>Methods:</b> We searched PubMed and Embase with an extensive search string and also assessed the references in the included studies. Two authors extracted the data independently. <b>Results:</b> We identified 20 studies that proposed in total 56 OEL values. Of these, two proposed a generic level for all MNMs, 14 proposed a generic OEL for a category of MNMs and 40 proposed an OEL for a specific nanomaterial. For specific fibers, four studies proposed a similar value but for carbon nanotubes (CNTs) the values differed with a factor ranging from 30 to 50 and for metals with a factor from 100 to 300. The studies did not provide explanations for this variation. We found that exposure to MNMs measured at selected workplaces may exceed even the highest proposed OEL. This indicates that the application and use of OELs may be useful for exposure reduction. <b>Conclusion:</b> OELs can provide a valuable reference point for exposure reduction measures in workplaces. There is a need for more and better supported OELs based on a more systematic approach to OEL derivation.

<b>研究背景：</b> 人工合成纳米材料（manufactured nanomaterials, MNMs）的毒理学特性与其块体材料存在差异，其对人体可能产生的不良健康影响仍存在不确定性。目前已提出多项职业接触限值（occupational exposure limits, OELs）相关提案，这些提案可用于风险管理与职业防护。本研究针对人工合成纳米材料的职业接触限值提案开展了系统综述，以期更好地明晰此类提案的覆盖范围及其推导方法。<b>研究方法：</b> 本研究通过构建全面的检索式检索PubMed与Embase数据库，并对纳入研究的参考文献进行了追溯核查。由两名研究者独立完成数据提取工作。<b>研究结果：</b> 本研究共纳入20项相关研究，累计提出56项职业接触限值。其中，2项提案针对所有人工合成纳米材料制定通用限值，14项提案针对某一类人工合成纳米材料制定通用职业接触限值，剩余40项提案则针对特定纳米材料制定职业接触限值。针对特定纤维类纳米材料，4项研究提出的限值较为接近；但对于碳纳米管（carbon nanotubes, CNTs），不同提案的限值差异可达30至50倍，金属类纳米材料的限值差异则在100至300倍之间。相关研究未对该差异作出解释。本研究发现，在部分选定作业场所中测得的人工合成纳米材料暴露水平甚至超过了已提出的最高职业接触限值，这表明应用职业接触限值有助于降低暴露风险。<b>研究结论：</b> 职业接触限值可为作业场所的暴露降低措施提供重要参考依据。未来亟需通过更系统的职业接触限值推导方法，制定更多、依据更充分的职业接触限值。