Concern over the effects of nanomaterials on human health has risen due to the dramatic advances in the development of various technologies based on nanomaterials. Gifu Prefecture and Gifu University are developing technologies for recycling used carbon fiber because the waste disposal process is highly cost and energy intensive. However, generation of carbon fiber dust during the recycling process is a serious issue, especially in the occupational environment. Recycling requires carbonization by partial firing treatment at 500℃ followed by firing treatment at 440℃: these processes produce dust as a by-product. It is important to study the influence of carbon fibers on human health at a molecular level. In this study, three types of carbon fibers - before recycling, after carbonization, and after firing were evaluated for their toxic effects on mice. During the breeding period, no loss in body weight was confirmed. Further, by staining the lung tissue sections, it was found that pulmonary fibrosis did not occur. We found that these carbon fibers might not possess severe toxicity. However, we also found that the toxicity varies according to firing treatment. Furthermore, we found that firing treatment reduces the potential hazard to human health.
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