According to a notice in the U.S. Environmental Protection Agency’s (EPA) May 11, 2009, Regulatory Agenda, a Toxic Substances Control Act (TSCA) Section 4(a) test rule “may be needed to determine the health effects” of multiwall carbon nanotubes (CNT). EPA states that the results of the tests that could be required under the rule could assist in understanding the health effects of the substance to manage/minimize any potential risk and exposure. Results could also help with establishing a correlation between the chemical/physical properties and health effects needed to protect the health of workers handling the substance. EPA has not determined when it will publish a notice of proposed rulemaking (NPRM).