Protection of Stratospheric Ozone: Listing of Substitutes for Ozone-Depleting Substances-n-Propyl Bromide

This action proposes to list n-propyl bromide (nPB) as an acceptable substitute for ozone-depleting substances (ODSs), subject to use conditions, in the solvent cleaning sector and aerosol solvents and adhesive end uses under the U.S. Environmental Protection Agency's (EPA or "we") Significant New Alternatives Policy (SNAP) program. The SNAP program implements section 612 of the amended Clean Air Act of 1990 (CAA), which requires EPA to evaluate substitutes for ODSs in order to reduce overall risk to human health and the environment. While we find that nPB has a short atmospheric lifetime and low ozone depletion potential when emitted from locations in the continental U.S., the Agency cautions that significant use of nPB closer to the equator poses significant risks to the stratospheric ozone layer. Further, if workplace exposure to nPB is poorly controlled, it may increase health risks to workers. In the interim, until the Occupational Safety and Health Administration (OSHA) develops a mandatory workplace exposure limit under Section 6 of the Occupational Safety and Health Act, the Agency recommends that users of nPB adhere to an acceptable exposure limit of 25 parts per million (ppm) over an eight-hour time-weighted average. In today's action, EPA proposes that the use of nPB is acceptable subject to a use condition, in a limited number of specific applications where emissions can be tightly controlled for both environmental and exposure concerns. The proposal only allows the use of nPB as a solvent in metals, precision, and electronics cleaning, and in aerosol solvent and adhesive end-uses. EPA is proposing to list nPB as an acceptable substitute for chlorofluorocarbon (CFC)-113, hydrochlorofluorocarbon (HCFC)-141b, and methyl chloroform when used in aerosol solvent and adhesive end uses, subject to the condition that nPB used in these end uses not contain more than 0.05% isopropyl bromide by weight before adding stabilizers or other chemicals. We are also proposing to list nPB as an acceptable substitute for CFC-113 and methyl chloroform in general metals cleaning, electronics cleaning, and precision cleaning, subject to the condition that nPB used in these end uses not contain more than 0.05% isopropyl bromide by weight before adding stabilizers or other chemicals.