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General Description

Synonyms: D5; cyclosiloxanes; polysiloxanes; cyclomethylsiloxanes; polydimethylsiloxanecyclic pentamer; organosilcone fluid; silicones

OSHA IMIS Code Number: M207

Chemical Abstracts Service (CAS) Registry Number: 541-02-6

Chemical Description and Physical Properties:

liquid
molecular weight: 370.85
vapor pressure: 30.002 mmHg @ -6.6°C
molecular formula: C10H30O5Si5
boiling point: 209.9°C
melting point: -40.9°C

Health Factors

Potential Symptoms: No human data available; INHAL CHRONIC (RATS): slight liver enlargement, weak "phenobarbital-like" induction of cytochrome P450 enzymes; significantly increased lung weight (at 160 ppm or higher).

Health Effects: Potential cumulative lung damage (HE10)

Affected Organs: Lungs

Notes:

  1. OSHA does not have a PEL for this chemical, which is used primarily in consumer product applications (e.g., bath oils, lotions, shampoos, shaving products, sprayed powders).
  2. The NOAEL for systemic toxicity in rats inhaling decamethylcyclopentasiloxane (D5) 6 hours/day for 28 days was reported to be 75 ppm.
  3. Two major, three minor and other trace metabolites were found in the urine of rats given a single oral dose of 14C-labeled D5. The major metabolites, which accounted for about 75% of total radioactivity in urine, were dimethylsilanediol and methylsilanetriol. The enzyme responsible for demethylation at the silicon-methyl bond has not been identified.
  4. A one-month recovery period did not reverse the focal macrophage accumulation and interstitial inflammation in lungs of rats that inhaled an average of 233 ppm, 6 hours/day, 5 days/week for 13 weeks.
  5. One year after a single injection of a mixture of cyclosiloxanes in female mice, D5 appeared to be retained to a greater extent than other cyclosiloxanes in lymph nodes, ovaries and abdominal fat.

Literature Basis:

  • Burns-Naas, L.A., et al.: Toxicology and humoral immunity assessment of decamethylcyclopentasiloxane (D5) following a 1-month whole body inhalation exposure in Fischer 344 rats. Toxicol. Sci. 43(1): 28-38, 1998.
  • Burns-Naas, L.A., Mast, R.W., Meeks, R.G., Mann, P.C. and Thevenaz, P.: Inhalation toxicology of decamethylcyclopentasiloxane (D5) following a 3-month nose-only exposure in Fischer 344 rats. Toxicol. Sci. 43(2): 230-240, 1998.
  • Kala, S.V., Lykissa, E.D., Neely, M.W. and Lieberman, M.W.: Low molecular weight silicones are widely distributed after a single subcutaneous injection in mice. Am. J. Pathol. 152(3): 645-649, 1998.
  • McKim, J.M., Jr., et al.: Induction of hepatic xenobiotic metabolizing enzymes in female Fischer-344 rats following repeated inhalation exposure to decamethylcyclopentasiloxane (D5). Toxicol. Sci. 50(1): 10-19, 1999.
  • Varaprath, S., McMahon, J.M. and Plotzke, K.P.: Metabolites of hexamethyldisiloxane and decamethylcyclopentasiloxane in Fischer 344 rat urine - a comparison of a linear and a cyclic siloxane. Drug Metab. Dispos. 31(2): 206-214, 2003.

Date Last Revised: 02/17/2005

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