Cancer morbidity investigations: lessons from the Duluth study of possible effects of asbestos in drinking water

Our plain-English summary of Cancer morbidity investigations: lessons from the Duluth study of possible effects of asbestos in drinking water, by E.E. Sigurdson, B.S. Levy, J. Mandel, et al (Environmental Research, 1981).

The study

• Authors: E.E. Sigurdson, B.S. Levy, J. Mandel, R. McHugh, L.J. Michienzi, H. Jagger, J. Pearson
• Journal: Environmental Research
• Published: 1981;25(1):50-61
• Cited by: 16 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. 000777).

In plain English

This paper reported surveillance of new gastrointestinal and lung cancers among residents of Duluth, Minnesota, in 1969-1974. Water samples from 1973 held 1 to 30 million amphibole fibers per liter of tap water; a federal court ruling had indicated they came from taconite tailings dumped into Lake Superior. Duluth's 1969-1971 rates were compared with Minneapolis and St. Paul, and its 1972-1974 rates with 1969-1971. Most rates were similar. In 1969-1971, pancreatic cancer was significantly higher in Duluth women than Minneapolis women, and in both sexes combined than in either city. That combined Duluth rate then fell significantly in 1972-1974. Cancers of the gastrointestinal tract 'not otherwise specified' were also significantly higher in Duluth males and both sexes combined than in either city in 1969-1971. The authors cautioned that these rates, especially this category, rested on small numbers. Male lung cancer fell significantly, probably reflecting smoking changes, the authors thought. In 16 of 24 comparisons, death rates gave more extreme relative risks than new-case rates. The authors concluded that too little time had passed to see associations with the exposure.

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: Cancer incidence (new-case) surveillance comparing Duluth with Minneapolis and St. Paul and with its own earlier period, plus a methodological comparison of incidence with mortality data
• Who was studied: Residents of Duluth, Minnesota (1970 population 100,478) diagnosed with gastrointestinal or lung cancer in 1969-1974; 352 gastrointestinal cancer cases in 1969-1971 and 328 in 1972-1974; comparison cities Minneapolis and St. Paul
• Exposure: Amphibole fibers in Duluth drinking water; 1973 samples contained 1 to 30 million amphibole fibers per liter of tap water. A federal court ruling had indicated that the fibers resulted from the dumping of taconite (iron ore) tailings into Lake Superior, which had gone on since 1955. A filtration plant removing 99.9% of fibers began operating in January 1977.
• Main results:
  • Pancreatic cancer, 1969-1971: the rate in Duluth females (13.80 per 100,000) was statistically significantly higher than in Minneapolis females (8.08)
  • Pancreatic cancer, both sexes combined: the Duluth rate (15.28) was statistically significantly higher than Minneapolis (10.69) and St. Paul (10.94) in 1969-1971. The Duluth rate fell to 9.74 in 1972-1974, and the article lists this decrease among the statistically significant differences.
  • Gastrointestinal tract not otherwise specified, 1969-1971: Duluth males 2.84 versus 0.28 (Minneapolis) and 0.21 (St. Paul); both sexes 2.16 versus 0.45 and 0.09; these differences were statistically significant
  • Lung cancer in Duluth males fell statistically significantly, from 74.39 (126 cases) in 1969-1971 to 65.64 (94 cases) in 1972-1974. The rate in females rose from 9.75 (19 cases) to 22.74 (34 cases). The authors thought these changes probably reflected smoking habits.
  • Of 255 people with gastrointestinal cancer who died, the death certificate agreed with the hospital record on the primary site in 176 (69%); in 38 (15%) the cause of death was coded to a disease other than cancer
  • For several sites, death rates in Duluth were substantially higher than in Minneapolis while the incidence rates were similar; mortality gave more extreme relative risks in 67% (16/24) of comparisons
  • In the workshop discussion, the first author reported about one-half to one case per year of pleural mesothelioma in Duluth over a recent 9-year period, the frequency expected from Third National Cancer Survey rates, and one case of peritoneal mesothelioma
• The authors' conclusion: The authors concluded that not enough time had passed to observe positive or negative associations between the exposure and cancer, so surveillance must continue. They also concluded that in Duluth, incidence data gave more conservative conclusions about environmental effects than mortality data.
• Limitations the authors state:
  • Some rates, especially for gastrointestinal tract not otherwise specified, were based on small numbers
  • Smoking habits of the Duluth population were not known
  • Surveillance began only about 10-15 years after exposure started and provides baseline data only

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Related studies

• Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota — B.S. Levy, E. Sigurdson, et al. (1976)
• Cancer incidence in relation to asbestos in drinking water in the Puget Sound region — L. Polissar, R.K. Severson, et al. (1982)
• A case-control study of asbestos in drinking water and cancer risk — L. Polissar, R.K. Severson, et al. (1984)
• Asbestos and drinking water in Canada — P. Toft, D. Wigle, et al. (1981)
• Asbestos-contaminated drinking water: its impact on household air — J.S. Webber, S. Syrotynski, et al. (1988)
• "Asbestos in drinking water and cancer incidence in the San Francisco Bay area" — K. Browne (1982)

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