From AAIA Capital Report

The U.S. Environmental Protection Agency (EPA) has issued a Significant New Use Rules (SNUR) for HFO-1234yf, which is being strongly considered as a substitute refrigerant for motor vehicle air conditioners due to its low impact on global warming. While SNUR identified health concerns if workers or consumers are exposed to significant amounts of the substance, EPA concluded that use of the refrigerant would not pose any serious adverse health or environmental concerns based on a determination that the charging of the refrigerant systems would only be done by vehicle manufacturers and that maintenance would only be performed by technicians certified under Section 609 of the Clean Air Act with EPA-approved equipment. 

The issuing of SNUR follows on the heels of another proposal from EPA to approve use 1234yf under the Significant New Alternatives Policy rule (SNAP). Authorized by the Clean Air Act, this program approves substitutes for ozone-depleting substances for various uses including motor vehicle air conditioning. The SNAP proposal would permit the use of 1234yf only in new vehicles, but did not approve retrofitting older vehicles based on flammability concerns. The SNAP proposal also included toxicity concerns for use by consumers of the product. 

The Automotive Aftermarket Industry Association (AAIA) and the Automotive Refrigerant Products Institute (ARPI) have submitted comments to the agency taking serious issues with the methodology used by EPA to determine whether 1234yf is safe for consumers to use. Pointing to studies used by the agency that severely overstated flammability risks, as well as exposure levels for consumers, AAIA and ARPI strongly opposed any restrictions on the use of 1234yf by consumers.  
 
Per request of AAIA and ARPI, EPA has extended to Feb. 24 the comment period on the SNAP rulemaking, which was originally expected to conclude Dec. 18. Also, SNUR was issued as a direct final rule, which would become effective April 2, unless the agency receives written adverse or critical comments, or notice of intent to submit adverse or critical comments before March 3.

Both AAIA and ARPI expect to oppose SNUR for many of the same reasons stated in comments submitted under the SNAP rulemaking.