SNUR means ‘significant new use rules’ and it’s been a long while since I’ve stumbled across any rulings from the US Environmental Protection Agency (EPA), which concern nanomaterials. From a September 30, 2022 news item on Nanotechnology News by Lynn L. Bergeson,

On September 29, 2022, the U.S. Environmental Protection Agency (EPA) issued final significant new use rules (SNUR) under the Toxic Substances Control Act (TSCA) for certain chemical substances that were the subject of premanufacture notices (PMN), including multi-walled carbon nanotubes (MWCNT) (generic). 87 Fed. Reg. 58999. See https://www.federalregister.gov/documents/2022/09/29/2022-21042/significant-new-use-rules-on-certain-chemical-substances-21-25e The SNUR requires persons who intend to manufacture (defined by statute to include import) or process the chemical substance identified generically as MWCNTs (PMN P-20-72) for an activity that is designated as a significant new use to notify EPA at least 90 days before commencing that activity. Persons may not commence manufacture or processing for the significant new use until EPA has conducted a review of the notice, made an appropriate determination on the notice, and taken such actions as are required by that determination. The SNUR will be effective on November 28, 2022.

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Hazard communication: Requirements as specified in 40 C.F.R. Section 721.72(a) through (d), (f), (g)(1), (g)(3), and (g)(5). For purposes of Section 721.72(g)(1), this substance may cause: eye irritation; respiratory sensitization; skin sensitization; carcinogenicity; and specific target organ toxicity. For purposes of Section 721.72(g)(3), this substance may cause unknown aquatic toxicity. Alternative hazard and warning statements that meet the criteria of the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) and Occupational Safety and Health Administration (OSHA) Hazard Communication Standard (HCS) may be used.

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The September 30, 2022 news item lists more significant new uses.