美国政府工业卫生的美国会议（ACGIH®) Threshold Limit Values for Chemical Substances (TLV®-CS）委员会已列入碳纳米管其2020化学物质和正在研究其他问题清单. Being placed on the under study list indicates that the TLV®-CS Committee has selected carbon nanotubes for development of a threshold limit value (TLV®）。ACGIH®描述的TLV®作为代表或低于TLV水平的科学界暴露的意见基于健康的价值观®does not create an unreasonable risk of disease or injury. The TLV®-CS委员会寻求实质性的数据和意见，并会只考虑卫生和曝光，而不是经济或技术可行性的解决这些问题。ACGIH®will update the under study list into a two-tier list by2020年7月31日:
- Tier 1 entries indicate the chemical substances and physical agents that may move forward as a notice of intended change (NIC) or notice of intent to establish (NIE) in the upcoming year, based on their status in the development process; and
- Tier 2 consists of those chemical substances and physical agents that will not move forward, but will either remain on, or be removed from, the under study list for the next year.
If the Committee decided to proceed with a proposed TLV®for carbon nanotubes, the ACGIH®Board of Directors would first ratify the proposed value, and it would be published as an NIE in the2020该TLV的年度报告®-CS Committee. The Committee included carbon nanotubes on its 2018 and 2019 lists of chemical substances and other issues under study.