A trial on the quantitative risk assessment of man-made mineral fibers by the rat intraperitoneal administration assay using the JFM standard fibrous samples

Our plain-English summary of A trial on the quantitative risk assessment of man-made mineral fibers by the rat intraperitoneal administration assay using the JFM standard fibrous samples, by S. Adachi, K. Kawamura, K. Takemoto (Industrial Health, 2001).

The study

• Authors: S. Adachi, K. Kawamura, K. Takemoto
• Journal: Industrial Health
• Published: 2001;39(2):168-74
• Cited by: 24 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We tried to evaluate the carcinogenic risk of man-made mineral fiber based on the mesothelioma incidence in female F344 rats after intraperitoneal administration. Rats (female F344/ Nslc, 5-week-old, n=330) were observed for 2 years after the intraperitoneal administration of 5 to 20 mg of 9 types of the JFM (Japan Fibrous Material Research Association) standard fiber samples (glass wool, rock wool, micro fiber glass, three types of refractory fiber, potassium titanate whisker, silicon carbide whisker, titanium oxide whisker), wollastonite (natural fiber) and UICC chrysotile B. All rats administered 10 mg of silicon carbide whisker had developed peritoneal mesothelioma within a year. The cumulative incidence of peritoneal mesothelioma at the end of the experiment was 85% for 10 mg UICC chrysotile B, 77% for 10 mg of potassium titanate whisker, 70% for 5 mg of silicon carbide whisker, 20% for 5 mg of potassium titanate whisker, 20% for 20 mg of refractory fiber 2 and 10% for 20 mg of refractory fiber 1. Carcinogenicity was estimated 2.4 times for silicon carbide whisker and 0.23 for potassium titanate whisker in comparison with UICC chrysotile B. It has been well documented from several experimental studies that man-made fibers are safer than asbestos because of the different durability in the lung. Present results consistently suggest that man-made fibers with high durability have similar or higher risk as carcinogen than asbestos.

In plain English

In this animal experiment, the authors injected 330 female F344 rats in the abdominal cavity with 5 to 20 mg of fibers and observed them for 2 years. The fibers came from the Japan Fibrous Material Research Association (JFM) standard set: glass wool, rock wool, micro glass fiber, refractory (ceramic) fibers, potassium titanate, silicon carbide and titanium oxide whiskers, and wollastonite. A comparison group received UICC chrysotile B asbestos. All rats given 10 mg of silicon carbide whisker developed peritoneal mesothelioma within a year. At two years, cumulative mesothelioma incidence was 85% for 10 mg chrysotile B, 77% for 10 mg potassium titanate whisker, 70% for 5 mg silicon carbide whisker, 20% for 5 mg potassium titanate whisker, 20% for 20 mg refractory fiber 2 and 10% for 20 mg refractory fiber 1. Compared with chrysotile B, potency was estimated at 2.4 times for silicon carbide whisker and 0.23 times for potassium titanate whisker. The authors noted that dosing by weight may have underestimated the potency of the refractory fibers, and that another exposure route could give different results. The authors concluded that man-made mineral fibers can have similar or higher carcinogenic potential than asbestos.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: animal experiment (intraperitoneal injection carcinogenicity assay in rats, 2-year observation)
• Who was studied: 330 female F344 rats, bought at 4 weeks old from Japan Slc and divided into 24 groups after a week of acclimatization
• Exposure: Single-substance intraperitoneal doses of JFM standard man-made mineral fibers (glass wool, rock wool, micro glass fiber, refractory fibers 1 to 3, potassium titanate whisker, silicon carbide whisker, titanium oxide whisker), wollastonite, or UICC chrysotile B, suspended in saline. All fibers were first tested at 10 mg per rat. Doses in a second experiment were raised to 20 mg or lowered to 5 mg per rat.
• Main results:
  • All rats given 10 mg of silicon carbide whisker developed peritoneal mesothelioma within a year.
  • In rats given 5 mg of silicon carbide whisker, mesothelioma incidence was 70% at one year.
  • Cumulative mesothelioma incidence at two years was 85% for 10 mg UICC chrysotile B and 77% for 10 mg potassium titanate whisker.
  • Cumulative incidence was 20% for 5 mg potassium titanate whisker, 20% for 20 mg refractory fiber 2 and 10% for 20 mg refractory fiber 1.
  • Peritoneal mesotheliomas were induced by 4 types of JFM standard fibers: silicon carbide whisker, potassium titanate whisker, refractory fiber 1 and refractory fiber 2.
  • The earliest mesothelioma appeared at 133 days, in a rat given 5 mg of silicon carbide whisker.
  • Tumors spread through the abdominal cavity, but no spread outside the abdomen was found.
  • Relative to UICC chrysotile B, carcinogenic potency was estimated at 2.4 times for silicon carbide whisker and 0.23 times for potassium titanate whisker.
  • The authors made a tentative calculation of lifetime cancer risk. Using the WHO figure for chrysotile, exposure to silicon carbide whisker at 0.5 × 10 to the minus 6 fiber/ml was estimated to cause one excess cancer death in 1,000,000 people.
• The authors' conclusion: The authors concluded that, for risk assessment in industrial settings, it is important to recognize that man-made mineral fibers can have similar or higher carcinogenic potential than asbestos. They also concluded that relative potency estimates from animal experiments allow a reasonable assessment of man-made mineral fibers.
• Limitations the authors state:
  • Doses were given by weight. Refractory fiber groups therefore received about 50 times fewer fibers than silicon carbide whisker groups, which may have led to underestimating the potency of refractory fibers.
  • The relative potency estimates assumed that differences in fiber number between silicon carbide whisker, potassium titanate whisker and chrysotile B were negligible.
  • The estimates come from intraperitoneal injection. Another route of exposure, or fibers of a different size, could give a different dose-response relationship.
  • Future studies would need to dose animals by the number of respirable fibers.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Carcinogenic, Mesothelioma, Wollastonite, UICC, Chrysotile, Peritoneal Mesothelioma.

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