Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota

Our plain-English summary of Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota, by B.S. Levy, E. Sigurdson, J. Mandel, et al (American Journal of Epidemiology, 1976).

The study

• Authors: B.S. Levy, E. Sigurdson, J. Mandel, E. Laudon, J. Pearson
• Journal: American Journal of Epidemiology
• Published: 1976;103(4):362-8
• Cited by: 56 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. 001114).

Abstract

The recent discovery of over one million asbestos-like fibers per liter of Duluth tap water and the suggestive evidence of a link between certain gastrointestinal (GI) cancers and work exposure to asbestos fibers in the air prompted this study. GI cancer incidence data were gathered for Duluth in the same manner as data previously gathered for comparison cities, Minneapolis and St. Paul. Although some differences in GI cancer incidence occurred among the three cities in 1969-1971, there was no consistent pattern of statistically significant differences observed. The number of GI cancers diagnosed in Duluth residents in 1972 was similar to that in each of the previous three years. This study represents the start of ongoing cancer surveillance in Duluth.

In plain English

This study asked whether gastrointestinal (GI) cancers were more common in Duluth, Minnesota, whose tap water had been found to contain over one million asbestos-like fibers per liter. GI cancer included cancers of the digestive tract, liver, gall bladder, pancreas and peritoneum. The authors collected records on Duluth residents first diagnosed 1969 through 1972, using methods earlier applied to Minneapolis and St. Paul, whose water was thought to contain few such fibers. For 1969-1971, adjusted rates for all GI cancers combined were higher in Minneapolis and St. Paul than in Duluth. In men and in women, Duluth had higher pancreatic cancer rates and lower large intestine and rectal cancer rates than both cities, but there was no consistent pattern of statistically significant differences. Duluth recorded 103 GI cancers in 1972, similar to each earlier year. No peritoneal mesotheliomas were found. Finding no excess in total GI cancer incidence, the authors concluded that the study suggested no effect in this period possibly attributable to the fibers. They called their data a baseline that does not rule out a later association, given the long delay before asbestos-associated cancers appear.

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: Population-based cancer incidence comparison and surveillance study. Duluth hospital and other records were abstracted using the same protocol as the Third National Cancer Survey, which had supplied the Minneapolis and St. Paul data.
• Who was studied: Residents of Duluth, Minnesota (1970 population 100,578) with GI cancer first diagnosed January 1969 through December 1972. GI cancer covered the esophagus, stomach, small intestine, large intestine, rectum and rectosigmoid, liver, gall bladder and biliary tract, pancreas, peritoneum, retroperitoneum and abdomen not otherwise specified, and GI tract not otherwise specified. Comparison groups were residents of Minneapolis (1970 population 434,400) and St. Paul (1970 population 309,980), using 1969-1971 data from the Third National Cancer Survey.
• Exposure: Drinking water from Lake Superior containing over one million asbestos-like fibers per liter. Electron microscope studies cited by the authors found one to 30 million amphibole asbestiform fibers per liter. A federal court attributed the fibers to taconite tailings dumped into the lake since 1955. Exposure was assigned by city of residence; no individual exposure was measured.
• Main results:
  • For 1969-1971, average annual age-and-sex-adjusted incidence rates for all GI cancers combined were greater in Minneapolis and St. Paul than in Duluth. The table shows, for both sexes, Duluth 85.91, Minneapolis 93.49 and St. Paul 96.02 per 100,000 population.
  • For both males and females, Duluth rates of pancreatic cancer were higher than those of Minneapolis and St. Paul, and Duluth stomach cancer rates were higher than those of Minneapolis.
  • For both males and females, Duluth rates of cancers of the large intestine and rectum/rectosigmoid were lower than those of Minneapolis and St. Paul.
  • Among age-and-sex subgroups, there was no consistent pattern of statistically significant rate differences for any GI cancer between Duluth and either comparison city.
  • GI cancers diagnosed in Duluth residents numbered 97 in 1969, 115 in 1970, 103 in 1971 and 103 in 1972. The 1972 count was similar to each of the previous three years.
  • No peritoneal mesotheliomas were identified in residents of any of the three cities in 1969-1971, nor in Duluth residents in 1972.
  • About 90 per cent of the cancers were confirmed under the microscope, with similar percentages in the three cities.
• The authors' conclusion: The authors concluded that the study detected no excess in total GI cancer incidence among Duluth residents in 1969-1972 and so suggested no effect in that period possibly attributable to the fibers. They regarded their data as baseline data that do not rule out an eventual association, and planned ongoing surveillance.
• Limitations the authors state:
  • The authors said the significance of the observed differences in rates of certain GI cancers could not yet be known.
  • The comparison cities' water was only thought to contain few, if any, asbestos-like fibers; this had not been established.
  • The data are best considered baseline because of the long lag between asbestos exposure and cancer and uncertainty about how long high fiber levels had been in Duluth water.
  • Duluth residents diagnosed in Twin Cities hospitals in 1972 were not captured; the authors estimated about two cases were missed.
  • Duluth 1972 data could be compared only with earlier Duluth data, because 1972 data for Minneapolis and St. Paul were not readily available.

Topics

Medical terms in this study, explained in our Lexicon: Discovery.

Related studies

• Observations of cancer incidence surveillance in Duluth, Minnesota — E.E. Sigurdson (1983)
• An investigation of the use of asbestos cement pipe for public water supply and the incidence of gastrointestinal cancer in Connecticut, 1935-1973 — J.M. Harrington, G.F. Craun, et al. (1978)
• Cancer morbidity investigations: lessons from the Duluth study of possible effects of asbestos in drinking water — E.E. Sigurdson, B.S. Levy, et al. (1981)
• Cancer of the gastrointestinal tract and exposure to asbestos in drinking water among lighthouse keepers (Norway) — K. Kjaerheim, B. Ulvestad, et al. (2005)
• Asbestiform amphibole minerals: detection and measurement of high concentrations in municipal water supplies — P.M. Cook, G.E. Glass, et al. (1974)
• Incidence of cancer among lighthouse keepers exposed to asbestos in drinking water — A. Andersen, E. Glattre, et al. (1993)

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