Vu V T, Lai D Y
Office of Pollution Prevention and Toxics, U.S. Environmental Protection Agency, Washington, D.C. 20460, USA.
Environ Health Perspect. 1997 Sep;105 Suppl 5(Suppl 5):1329-36. doi: 10.1289/ehp.97105s51329.
Naturally occurring and man-made (synthetic) fibers of respirable sizes are substances that have been identified by the U.S. Environmental Protection Agency (U.S. EPA) as priority substances for risk reduction and pollution prevention under the Toxic Substances Control Act (TSCA). The health concern for respirable fibers is based on the link of occupational asbestos exposure and environmental erionite fiber exposure to the development of chronic respiratory diseases, including interstitial lung fibrosis, lung cancer, and mesothelioma in humans. There is also considerable laboratory evidence indicating that a variety of fibers of varying physical and chemical characteristics can elicit fibrogenic and carcinogenic effects in animals under certain exposure conditions. This paper discusses key scientific issues and major default assumptions and uncertainties pertaining to the risk assessment of inhaled fibers. This is followed by a description of the types of assessment performed by the U.S. EPA to support risk management actions of new fibers and existing fibers under TSCA. The scope and depth of these risk assessments, however, vary greatly depending on whether the substance under review is an existing or a new fiber, the purpose of the assessment, the availability of data, time, and resources, and the intended nature of regulatory action. In general, these risk assessments are of considerable uncertainty because health hazard and human exposure information is often incomplete for most fibers. Furthermore, how fibers cause diseases and what specific determinants are critical to fiber-induced toxicity and carcinogenicity are still not completely understood. Further research to improve our knowledge base in fiber toxicology and additional toxicity and exposure data gathering are needed to more accurately characterize the health risks of inhaled fibers.
可吸入尺寸的天然和人造（合成）纤维是美国环境保护局（U.S. EPA）根据《有毒物质控制法》（TSCA）确定的需要降低风险和预防污染的优先物质。对可吸入纤维的健康担忧基于职业性石棉暴露以及环境中毛沸石纤维暴露与人类慢性呼吸道疾病（包括间质性肺纤维化、肺癌和间皮瘤）发展之间的联系。也有大量实验室证据表明，在特定暴露条件下，各种物理和化学特性不同的纤维可在动物体内引发纤维化和致癌作用。本文讨论了与吸入纤维风险评估相关的关键科学问题、主要默认假设和不确定性。接下来描述了美国环境保护局为支持《有毒物质控制法》下新纤维和现有纤维的风险管理行动而进行的评估类型。然而，这些风险评估的范围和深度差异很大，这取决于所审查的物质是现有纤维还是新纤维、评估目的、数据可用性、时间和资源以及监管行动的预期性质。一般来说，这些风险评估存在很大的不确定性，因为大多数纤维的健康危害和人体暴露信息往往不完整。此外，纤维如何导致疾病以及哪些具体决定因素对纤维诱导的毒性和致癌性至关重要，目前仍未完全了解。需要进一步开展研究以改善我们在纤维毒理学方面的知识基础，并收集更多毒性和暴露数据，以便更准确地描述吸入纤维的健康风险。
