Talc-treated rice and Japanese stomach cancer

Our plain-English summary of Talc-treated rice and Japanese stomach cancer, by R.R. Merliss (Science, 1971).

The study

• Author: R.R. Merliss
• Journal: Science
• Published: 1971;173(4002):1141-2
• Cited by: 68 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002448).

Abstract

The Japanese prefer talc-dusted rice in their diet. The incidence of stomach cancer in Japan is unusually high. Most talc has some asbestos contaminants. Epidemiologic evidence is presented that the asbestos-contaminated talc on rice in the diet is the carcinogen or cocarcinogen responsible for the high incidence of Japanese stomach cancer.

In plain English

This 1971 report in Science put forward a hypothesis, not a new epidemiologic study. The author proposed that asbestos-contaminated talc added to rice for Japanese consumers was the carcinogen or cocarcinogen behind Japan's high stomach cancer rate. Optical microscopy of ash from rice sold in a Los Angeles market for Japanese customers showed 3.7 x 10^6 (3.7 million) asbestos-form fibers per gram. The author also noted that such rice containers usually bore the label "Coated with glucose and talc." The author described California and New York talcs as containing fibrous silicates including tremolite and anthophyllite, with possible chrysotile contamination. Most other evidence came from earlier studies the author cited. These included stomach cancer incidence of 77.9 per 100,000 in Japanese men in Japan (1962 to 1964), versus 45 per 100,000 in Japanese men in Hawaii and 9.2 and 8.3 in Chinese and Caucasian men there. The author concluded that the hypothesis appeared to fit the known epidemiology of stomach cancer in Japan. The author noted high mortality also in Chile, Finland and Iceland, where rice is not a major staple, and called for further studies.

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: Short report presenting a hypothesis, supported by one microscopy observation of rice ash, a note on rice package labels, and data cited from earlier published studies; not an original epidemiologic study
• Who was studied: A specimen of rice intended for Japanese consumers, bought in a Los Angeles market; the population figures discussed (Japanese men in Japan and Hawaii, Chinese and Caucasian men in Hawaii) come from other studies the author cited
• Exposure: Ingestion of rice coated with glucose and talc; commercial talc from New York and California described as containing fibrous silicates including the amphiboles anthophyllite and tremolite, with chrysotile as a possible contaminant
• Main results:
  • Optical microscopy of the ash of the store-bought rice specimen showed 3.7 x 10^6 asbestos-form fibers per gram (the article's own observation)
  • The author noted that rice containers in Los Angeles markets intended for Japanese customers usually bore the label "Coated with glucose and talc"
  • Cited from another source: 2 percent of all talc produced in California from 1959 to 1963 was used as a rice additive, mainly for export to Japan
  • Cited from earlier data: stomach cancer incidence in Japanese males in Japan in 1962 to 1964 was 77.9 per 100,000
  • Cited from earlier data: Japanese men in Hawaii had an incidence of 45 per 100,000, compared with 9.2 for Chinese men and 8.3 for Caucasian men in Hawaii
• The authors' conclusion: The author concluded that the hypothesis that asbestos-containing talc on rice causes the high incidence of stomach cancer in Japan appeared to satisfy the known epidemiology of that cancer in Japan
• Limitations the authors state:
  • The author acknowledged that stomach cancer mortality rates were also high in Chile, Finland and Iceland, where rice is not a major dietary staple, and suggested that talc additives in other popular foods be suspected there
  • The author stated that further studies of talc and asbestos contamination of the common diet in high-incidence countries were needed

Topics

The National Library of Medicine indexes this study under subjects our site covers: Stomach cancer, Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: Talc, Stomach Cancer.

Related studies

• Talc-coated rice as a risk factor for stomach cancer — G.N. Stemmermann, L.N. Kolonel (1978)
• Exposure to nitrosamines, carbon black, asbestos, and talc and mortality from stomach, lung, and laryngeal cancer in a cohort of rubber workers — K. Straif, U. Keil, et al. (2000)
• Talc exposure and risk of stomach cancer: Systematic review and meta-analysis of occupational cohort studies — C.J. Chang, Y.K. Tu, et al. (2020)
• Stomach Cancer and Exposure to Talc Powder without Asbestos via Chinese Herbal Medicine: A Population-Based Cohort Study — C.J. Chang, Y.H. Yang, et al. (2019)
• Analysis of particles in stomach tumours from Japanese males — W.J. Henderson, D.M. Evans, et al. (1975)
• Asbestos, talc and nitrites in relation to gastric cancer — W.E. Smith (1973)

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