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Suggested Citation:"REFERENCES." 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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INTRODUCTION 13 Another consideration in the derivation of the EEGLs and CEGLs is the inhalation toxicokinetics of the HFCs. In general, the uptake of an inhaled HFC is a function of the rate of respiration (pulmonary ventilation), solubility of the HFC in the blood (blood:gas partition coefficient), pulmonary blood flow (cardiac output), and partial pressure of HFC in the blood. Because of the marked difference in pulmonary ventilation between rodents and humans, rodents will reach a constant HFC arterial pressure much more rapidly than will humans. These differences could be important for short-term exposures, but would likely be of less importance for long-term exposures where both humans and rodents would ultimately reach steady-state arterial concentrations of the gases. STRUCTURE OF THE REPORT The results of the subcommittee's evaluation of HFC-236fa, HFC-23, and HFC-404a are presented in Chapter 2, Chapter 3, and Chapter 4, respectively. For each agent, the subcommittee evaluates inhalation data on the toxicokinetics; acute, subchronic, and chronic toxicity; reproductive effects; developmental effects; genotoxicity; and carcinogenic effects. In addition, special consideration is given to data on cardiac sensitization because inhalation of HFCs and similar compounds are known to make the mammalian heart abnormally sensitive to epinephrine, resulting in cardiac arrhythmia and possibly death. REFERENCES NRC (National Research Council). 1986. Criteria and Methods of Preparing Emergency Exposure Guidance Level (EEGL), Short-Term Public Emergency Guidance Level (SPEGL), and Continuous Exposure Guidance Level (CEGL) Documents. Washington D.C: National Academy Press. NRC (National Research Council). 1992. Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants. Washington D.C: National Academy Press. NRC (National Research Council). 1993. Guidelines for Developing Community Emergency Exposure Levels for Hazardous Substances. Washington D.C: National Academy Press. NRC (National Research Council). 1996. Toxicity of Alternatives to Chlorofluorocarbons: HFC-134a and HCFC-123. Washington D.C: National Academy Press.

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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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