On September 17, 2010, the U.S. Environmental Protection Agency (EPA) issued final significant new use rules (SNUR) for two chemical substances that were the subject of premanufacture notices (PMN). The two chemical substances are identified generically as multi-walled carbon nanotubes (MWCNT) (PMN P08177) and single-walled carbon nanotubes (SWCNT) (PMN P08328). Persons who intend to manufacture, import, or process either of these substances for a use that is designated as a significant new use by the final rule must notify EPA at least 90 days before commencing that activity. EPA states that it believes the SNURs are necessary because these chemical substances may be hazardous to human health and the environment. The required notification would provide EPA with the opportunity to evaluate the intended use and, if necessary, to prohibit or limit that activity before it occurs. The final rule is effective October 18, 2010.

EPA issued direct final SNURs on these two substances on June 24, 2009. EPA withdrew the notices on August 21, 2009, after receiving notices of intent to submit adverse comments on the SNURs. EPA issued proposed SNURs on November 6, 2009. In response to comments on the applicability of the SNURs for these chemicals, EPA has included clarifying language for those forms of the subject PMN substances that are exempt from the provisions of the SNURs.  These exemptions apply to quantities of the PMN substances: after they have been completely reacted (cured); incorporated or embedded into a polymer matrix that itself has been reacted (cured); or embedded in a permanent solid polymer form that is not intended to undergo further processing except for mechanical processing. In response to comments on the basis for the SNURs, EPA developed revised human health effects and environmental effects summaries for carbon nanotubes (CNT).