On August 18, 2021, the U.S. Environmental Protection Agency (EPA) issued several significant new use rules (SNUR) under the Toxic Substances Control Act (TSCA) for chemical substances that were the subject of premanufacture notices (PMN), including the chemical substance identified generically as multiwalled carbon nanotubes (PMN P-18-182). 86 Fed. Reg. 46133. The SNUR requires persons who intend to manufacture (defined by statute to include import) or process multiwalled carbon nanotubes (PMN P-18-182) for an activity that is designated as a significant new use to notify EPA at least 90 days before commencing that activity. The requirements of the SNUR do not apply to quantities of the substance that have been:

1. Embedded or incorporated into a polymer matrix that itself has been reacted (cured);

2. Embedded in a permanent solid/polymer form that is not intended to undergo further processing, except mechanical processing; or

3. Incorporated into an article as defined at 40 C.F.R. Section 720.3(c).

Under the SNUR, it is a significant new use to use an application method that generates a dust, mist, or aerosol, unless such application method occurs in an enclosed process. It is a significant new use to use the substance other than for heat transfer, heat storage, thermal emission, and general temperature management in heat-generating systems such as electronics, to improve mechanical properties or electrical conductivities of other materials or products, and for light absorption properties. The SNUR will be effective on October 18, 2021.