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Suggested Citation:"4 Hydrofluorocarbon-404a." National Research Council. 2000. Submarine Exposure Guidance Levels for Selected Hydrofluorocarbons: HFC-236fa, HFC-23,and HFC-404a. Washington, DC: The National Academies Press. doi: 10.17226/9815.
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Page 40

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HYDROFLUOROCARBON-404A 40 4 Hydrofluorocarbon-404a YDROFLUOROCARBON (HFC)-404a is a gaseous mixture of three halocarbons —52% HFC-143a, 44% HFC-125, and 4% HFC-134a. It is used as a refrigerant in ice-cream machines. The U.S. Navy is considering installing a single ice- cream machine aboard each of its submarines. The Navy does not intend to perform servicing of this equipment when its submarines are under way, so the only HFC-404a aboard will be in the ice cream machine (i.e, there will be no cylinders of HFC-404a aboard). The refrigerant systems of the machines are sealed and operate in a manner similar to that of a household refrigerator. To protect submariners from large accidental releases or low-level slow releases of HFC-404a, emergency exposure guidance levels (EEGLs) and continuous exposure guidance levels (CEGLs) are needed to avoid adverse health effects from short-term or prolonged exposures to HFC-404a and to avoid degradation in crew performance. No toxicity studies on HFC-404a were available, so the subcommittee reviewed the available data on its three components—HFC-143a, HFC-125, and HFC-134a. The subcommittee used these data to determine 1-hr and 24-hr EEGLs and 90-day CEGLs for each of the components, and then those values were used to calculate exposure guidance levels for HFC-404a on the basis of percent composition of the individual components. The calculated EEGLs and CEGL for HFC-404a were used to evaluate the Navy's proposed exposure guidance levels for HFC-404a.

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As part of the effort to phase out the use of stratospheric ozone-depleting substances, such as chlorofluorocarbons (CFCs), the U.S. Navy is considering hydrofluorocarbons (HFCs) as replacements for the CFC refrigerants used aboard its submarines. Before using the HFCs, the Navy plans to set emergency exposure guidance levels (EEGLs) and continuous exposure guidance levels (CEGLs) to protect submariners from health effects that could occur as a result of accidental releases or slow leaks.

In this report, the Subcommittee on Exposure Guidance Levels for Selected Hydrofluorocarbons of the National Research Council's (NRC 's) Committee on Toxicology independently reviews the scientific validity of the Navy's proposed 1-hr and 24-hr EEGLs and 90-day CEGLs for two of the candidate refrigerants-HFC-236fa and HFC-404a. In addition, the subcommittee reviews the the EEGLs and CEGL for HFC-23, one of the combustion products of HFC-236fa. This NRC report is intended to aid the Navy in using HFCs safely.

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