The American Conference of Governmental Industrial Hygienists (ACGIH®) Threshold Limit Values for Chemical Substances (TLV®-CS) Committee has included carbon nanotubes on its 2021 list of chemical substances and other issues under study. 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® describes TLVs® as health-based values representing the opinion of the scientific community that exposure at or below the level of the TLV® does not create an unreasonable risk of disease or injury. The TLV®-CS Committee seeks substantive data and comments and will consider only those addressing issues of health and exposure, not economic or technical feasibility. ACGIH® will update the under study list into a two-tier list by July 31, 2021:
- 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 the 2021 annual report of the TLV®-CS Committee. The Committee included carbon nanotubes on its 2018, 2019, and 2020 lists of chemical substances and other issues under study.