Perspectives on refractory ceramic fiber (RCF) carcinogenicity: comparisons with other fibers

In 2011, SCOEL classified RCF as a secondary genotoxic carcinogen and supported a practical threshold. Inflammation was considered the predominant manifestation of RCF toxicity. Intrapleural and intraperitoneal implantation induced mesotheliomas and sarcomas in laboratory animals. Chronic nose-only inhalation bioassays indicated that RCF exposure in rats increased the incidence of lung cancer and similar exposures resulted in mesothelioma in hamsters, but these studies may have been compromised by overload. Epidemiological studies in the US and Europe showed an association between exposure and prevalence of respiratory symptoms and pleural plaques, but no interstitial fibrosis, mesotheliomas, or increased numbers of lung tumors were observed. As the latency of asbestos induced mesotheliomas can be up to 50 years, the relationship between RCF exposure and respiratory malignances has not been fully determined. Nonetheless, it is possible to offer useful perspectives. RCF and rock wool have similar airborne fiber dimensions and biopersistence. Therefore, it is likely that these fibers have similar toxicology. Traditional rock wool has been the subject of numerous cohort and case control studies. For rock wool, IARC () concluded that the epidemiological studies did not provide evidence of carcinogenicity. Based on analogies with rock wool (read across), it is reasonable to believe that increases in lung cancer or any mesotheliomas are unlikely to be found in the RCF-exposed cohort. RCF producers have developed a product stewardship program to measure and control fiber concentrations and to further understand the health status of their workers.

2011年，职业暴露限值科学委员会（SCOEL）将耐火陶瓷纤维（Refractory Ceramic Fibers，RCF）归类为次级遗传毒性致癌物，并支持存在实际阈值。炎症被认为是RCF毒性的主要表现形式。胸膜腔内与腹腔内植入染毒可在实验动物体内诱导生成间皮瘤与肉瘤。慢性仅鼻部吸入染毒生物测定实验结果显示，大鼠暴露于RCF会提升肺癌发病率，而类似染毒条件下仓鼠可诱发间皮瘤，但此类研究或因纤维过载而存在方法学局限性。美国与欧洲的流行病学研究表明，RCF暴露与呼吸道症状患病率及胸膜斑块形成存在关联，但未观察到间质性纤维化、间皮瘤或肺肿瘤数量增加的情况。由于石棉诱导的间皮瘤潜伏期可长达50年，RCF暴露与呼吸道恶性肿瘤之间的关联尚未完全明确。即便如此，仍可提供具有参考价值的研究视角。RCF与岩棉具有相似的空气传播纤维尺寸与生物持久性，因此两类纤维的毒理学特性大概率相近。传统岩棉已成为众多队列研究与病例对照研究的研究对象。国际癌症研究机构（International Agency for Research on Cancer，IARC）针对岩棉得出结论，相关流行病学研究未提供其致癌性证据。基于与岩棉的交叉参照法（read across），我们有理由认为，在RCF暴露队列中不太可能观察到肺癌或任何间皮瘤的发病率上升。RCF生产商已制定产品管理计划，用于检测与控制纤维浓度，并进一步掌握其员工的健康状况。