Under Section 612 of the Clean Air Act (CAA), EPA’s Significant New Alternatives Policy (SNAP) program reviews substitutes within a comparative risk framework in the following industrial sectors:

The SNAP program does not provide a static list of alternatives but instead, evolves the list as EPA makes decisions that are informed by its overall understanding of the environmental and human health impacts as well as its current knowledge about available substitutes. Section 612 also provides that EPA must prohibit the use of a substitute where EPA has determined that there are other available substitutes that pose less overall risk to human health and the environment.

Basics of the SNAP Program

• A. What is the purpose of the SNAP program?

  The SNAP program is designed to:

  • Identify and evaluate substitutes in end-uses that have historically used ozone-depleting substances (ODS);
  • Look at overall risk to human health and the environment of both existing and new substitutes;
  • Publish lists of acceptable and unacceptable substitutes by end-use;
  • Promote the use of acceptable substitutes; and
  • Provide the public with information about the potential environmental and human health impacts of substitutes.

  To arrive at determinations on the acceptability of substitutes, the Agency performs a cross-media analysis of risks to human health and the environment from the use of various substitutes in different industrial and consumer uses that have historically used ODS. EPA reviews characteristics, including the following, when evaluating each proposed substitute:

  • Ozone depletion potential (ODP),
  • Global warming potential (GWP),
  • Toxicity,
  • Flammability,
  • Occupational and consumer health/safety,
  • Local air quality, and
  • Ecosystem effects.

  See Question C, below, for further information regarding EPA’s evaluation.

• B. What are the guiding principles of the SNAP program?

  The guiding principles of the SNAP program are:

  • Evaluate substitutes within a comparative risk framework
  • Do not require that substitutes be risk-free to be found acceptable
  • Restrict only those substitutes that are significantly worse
  • Evaluate risks by use
  • Provide the regulated community with information as soon as possible
  • Do not endorse products manufactured by specific companies
  • Defer to other environmental regulations when warranted
• C. What are EPA's criteria for evaluating alternatives?

  EPA's decision on the acceptability of new substitutes proposed by manufacturers, formulators, or users is based primarily on the potential human health and environmental risks posed by the substitutes as compared other substitutes available for a particular end-use. EPA's evaluation of each substitute in an end-use is based on the following types of information and analyses:

  • Atmospheric effects―The SNAP program considers the ODP and 100-year integrated GWP of compounds to assess atmospheric effects.
  • Exposure assessments―Exposure assessments are used to estimate concentration levels of substitutes to which workers, consumers, the general population, and environmental receptors may be exposed over a determined period of time. These assessments are based on personal monitoring data or area sampling data if available. Exposure assessments may be conducted for many types of releases including:
    • Releases in the workplace and in homes
    • Releases to ambient air and surface water
    • Releases from the management of solid wastes
  • Toxicity data―Toxicity data is used to assess the possible health and environmental effects for exposure to substitutes. The Occupational Safety and Health Administration (OSHA) or EPA approve wide health-based criteria that are available for a substitute such as:
    • Permissible exposure limits (PELs for occupational exposure)
    • Inhalation reference concentrations (RfCs for non-carcinogenic effects on the general population)
    • Cancer slope factors (for carcinogenic risk to members of the general population)

  If OSHA has not issued a PEL for a compound, EPA also considers Workplace Environmental Exposure Limits (WEEL) set by the American Industrial Hygiene Association (AIHA), threshold limit values (TLV) set by the American Conference of Governmental Industrial Hygienists (ACGIH), or Recommended Exposure Limits (REL) set by the National Institutes of Occupational Safety and Health (NIOSH). If limits for occupational exposure or exposure to the general population are not already established, then EPA derives these values following the Agency's peer-reviewed guidelines. If a manufacturer provides a recommended exposure limit, EPA would review the information used in derivation and compare to its own exposure limit derivation. Exposure information is combined with this toxicity information to explore any basis for concern. Toxicity data is used with existing EPA guidelines to develop health-based criteria for interim use in these risk characterizations.

  • Flammability―Flammability is examined as a safety concern for workers and consumers. EPA assesses flammability risk using data on:
    • Flash point and flammability limits (e.g., OSHA flammability/ combustibility classifications)
    • Data on testing of blends with flammable components
    • Test data on flammability in consumer applications conducted by independent laboratories
    • Information on flammability risk minimization techniques
  • Other environmental impacts―The SNAP program also examines other potential environmental impacts such as ecotoxicity and local air quality impacts. A compound that is likely to be discharged to water may be evaluated for impacts on aquatic life. Some substitutes are volatile organic compounds (VOCs), which are chemicals that increase tropospheric air pollution by contributing to ground-level ozone formation. In addition, EPA notes whenever a potential substitute is considered a hazardous air pollutant or hazardous waste.

  40 CFR 82.178 details the specific data to be submitted.

SNAP Regulations

• D. How do the SNAP listings work?

  EPA's classifications of decisions on alternative substitutes are the following:

  • Acceptable substitutes are determined to reduce overall risk to human health and the environment compared to other substitutes for the particular end-use. These alternatives may be used without restriction in the specified end-uses.
  • Acceptable subject to use conditions indicates that a substitute is acceptable only if used in a certain way. For example, substitutes in motor vehicle air conditioning systems are acceptable subject to a use condition that the substitute be used with unique equipment fittings on the system (for servicing) and on refrigerant containers.
  • Acceptable subject to narrowed use limits indicates that a substitute may be used only within certain specialized applications within a sector and end-use, and may not be used for other applications within an end-use or sector. The Agency requires a user of a narrowed use substitute to demonstrate that no other acceptable substitutes are available for their specific application.
  • Unacceptable alternatives are prohibited because the Administration has determined the use of the substitutes pose significantly higher human health and environmental risks than those risks from use of other available or potentially available substitutes.

  Use conditions and narrowed use limits are both considered “use restrictions.” For example, in the aerosols and solvents sectors, EPA does not list individual companies' products. Instead, the acceptability decisions are for specific compounds (e.g., trichloroethylene), for classes of substitute compounds (e.g., oxygenated organic solvents), or for alternative technologies (e.g., hot-melt adhesives). EPA publishes decisions made under the SNAP program in the Federal Register. All SNAP Rules and Notices are available online on the Regulations page.

• E. What is the difference between a 'Notice,' a 'Proposed Rule' (Proposal), and a 'Final Rule' (Rule)?

  ‘Notice’
  Substitutes found acceptableacceptableThis designation means that a substitute may be used, without restriction, to replace the relevant ODS within the end-use specified. For example, HCFC-22 is an acceptable substitute for R-502 in industrial process refrigeration. Note that all SNAP determinations apply to the use of a specific product as a substitute for a specific ODS in a specific end-use. without restriction will be published in a determination or notice of acceptability, or ‘Notice.’ This 'Notice' contains no regulatory controls and thus does not need to go through the notice-and-comment rulemaking process. It may contain technical corrections to earlier rules as well as listings of new agents that are acceptable without restrictions. It enters into force upon publication in the Federal Register.

  ‘Proposed Rule’ (Proposal)
  Substitutes that are found unacceptableunacceptableThis designation means that it is illegal to use a product as a substitute for an ODS in a specific end-use. For example, HCFC-141b is an unacceptable substitute for CFC-11 in building chillers. Note that all SNAP determinations apply to the use of a specific product as a substitute for a specific ODS in a specific end-use. or acceptable subject to use restrictions will go through a comment period and then be published as a rule. A 'Proposed Rule' (Proposal) contains proposed lists of agents deemed acceptable (but subject to narrowed use limits or use conditions) or unacceptable. There is usually a 60-day public comment period beginning with the date of publication in the Federal Register.

  ‘Final Rule’ (Rule)
  After the public has an opportunity to comment on EPA's proposed rules, EPA considers the comments and prepares and publishes a 'Final Rule' (Rule) that enacts the provisions into law.
  The SNAP rules and notices are available online on the Regulations page and can also be ordered for a nominal fee from the Government Printing Office, (202) 512-1800, or fax (202) 512-2250.

• F. Whom do I contact for more information on the SNAP Program or about substitutes in each industrial sector?

  For more information on the SNAP program, substitutes, or how to submit a substitute under SNAP, please contact the SNAP Coordinator at 202-564-7768 or Chenise Farquharson (farquharson.chenise@epa.gov). Interested parties may also contact the Stratospheric Protection Division via

  Email: spdcomment (spdcomment@epa.gov)

  Mail at:
  Stratospheric Protection Division
  Mail Code 6205T
  1200 Pennsylvania Avenue, NW
  Washington, DC 20460