National Academies Press: OpenBook
« Previous: TOXICOKINETICS
Suggested Citation:"Acute Toxicity." 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.
×
Page 16

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

HYDROFLUOROCARBON-236FA 16 biphasic with a rapid equilibration phase of up to 30 min followed by a slow linear uptake phase. The partition-coefficient data and the data obtained from the gas-uptake experiments were used in a physiologically based pharmacokinetic (PB-PK) model in an attempt to describe mathematically the disposition and metabolism of HFC-236fa. The PB-PK model was unable to describe adequately the loss of the test material from the animal chamber. Data from the gas-uptake experiments were inconsistent with metabolism-mediated disappearance of HFC-236fa. Samples of blood, urine, or feces were collected from rats exposed to HFC-236fa after 6 and 24 hr of exposure (Vinegar et al. 1995). The samples were extracted with hexane or cyclohexane and analyzed by gas chromatography and mass spectrometry (GC-MS); some samples were methylated before GC-MS analysis to detect organic acids. Although HFC-236fa was detected in samples of blood, urine, or feces, no fluorocarbon metabolites of HFC-236fa were detected by GC-MS, either in the total-ion- current mode or in the single-ion-monitoring mode. Moreover, GC-MS analysis revealed no compounds with retention times consistent with seven fluorocarbons proposed as possible metabolites of HFC-236fa. Valentine (1995) found no fluoride ions in the urine of rats exposed to HFC-236fa concentrations as high as 50,000 ppm for 6 hr per day, 5 days per week for 2 weeks, thereby indicating no significant metabolism of the compound. TOXICITY INFORMATION Acute Toxicity Currently available data indicate that HFC-236fa has low acute toxicity by the inhalation route. Keller (1994) exposed young male rats to concentrations of HFC-236fa at 150,000 or 200,000 ppm (purity 99.06%) for 4 hr. Actual mean concentrations were approximately 134,000 and 189,000 ppm, respectively. During the whole-body exposure, the oxygen concentration was maintained at 21% ± 3% and air flow was approximately 2 liters (L) per min with a total chamber volume of 13 L. No rats died during exposure or during an additional day of observation following the exposure. Exposure to HFC-236fa at 134,000 ppm produced no observable effects, but rats exposed at 189,000 ppm exhibited narcosis (nonresponsive to sound) that persisted for approximately 30 min after cessation of exposure. No additional effects were observed during the 1-day post-exposure period, and no patho

Next: Cardiac Sensitization »
Submarine Exposure Guidance Levels for Selected Hydrofluorocarbons: HFC-236fa, HFC-23,and HFC-404a Get This Book
×
Buy Paperback | $29.00 Buy Ebook | $23.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

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.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!