Incidence of cancer among lighthouse keepers exposed to asbestos in drinking water

Our plain-English summary of Incidence of cancer among lighthouse keepers exposed to asbestos in drinking water, by A. Andersen, E. Glattre, B.V. Johansen (American Journal of Epidemiology, 1993).

The study

• Authors: A. Andersen, E. Glattre, B.V. Johansen
• Journal: American Journal of Epidemiology
• Published: 1993;138(9):682-7
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The study population comprises 690 Norwegian male lighthouse keepers whose water supply came from cisterns that received rain water off asbestos-cement-tiled roofs. The asbestos-cement tiles were installed in the late 1950s, and two decades later the fiber content in the tap water was analyzed. The fiber content ranged from 1,760 to 71,350 million fibers per liter, which is significantly higher than measured in any other Norwegian public water supply. During the follow-up period, 1960-1991, no statistically significant excess risk was found for any type of cancer in the group with a latency period of 20 years or more, except for stomach cancer (11 observed cases vs. 4.57 expected, standardized incidence ratio = 241, 95% confidence interval 120-431). No cases of malignant mesothelioma were found. The study is limited by lack of knowledge as to when the tiles began to deteriorate and, thus, the magnitude of total exposure as well as by the inability to control for such potential confounding factors as diet.

In plain English

This Norwegian cohort study followed 690 male lighthouse keepers, alive on January 1, 1960, whose water came from cisterns collecting rain off asbestos-cement roof tiles installed in the late 1950s. Tap water from seven lighthouse cisterns, tested in 1983, held 1,760 to 71,350 million fibers per liter. Chrysotile made up 92 percent of the tile material. Cancers in 1960-1991 were compared with expected numbers from rural Norwegian rates. In all, 140 cancers occurred against 134.2 expected. For digestive-tract cancer the standardized incidence ratio (SIR) was 129 (42 observed vs. 32.52 expected, 95 percent CI 93-175), not statistically significant. The one significant excess was stomach cancer 20 or more years after first exposure: SIR 241, 11 cases, 95 percent CI 120-431. No malignant mesothelioma was found, though only 0.41 were expected. The authors concluded the exceptionally large fiber numbers at some lighthouses might increase gastrointestinal cancer risk, but this was difficult to explore. They noted that the stomach excess might instead reflect a diet of dried, salted and smoked food, that the group was small, and that it was unknown when the tiles began to erode.

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: Cohort study comparing observed with expected cancer cases (standardized incidence ratios), with expected numbers based on rates in the rural Norwegian population
• Who was studied: 690 Norwegian male lighthouse employees (from those working at lighthouses 1920-1966) alive on January 1, 1960, followed for cancer and death to the end of 1991; 15,187 person-years
• Exposure: Asbestos fibers in drinking water from cisterns fed by rain water off asbestos-cement roof tiles installed in the late 1950s; tap water from seven lighthouse cisterns analyzed in 1983 contained 1,760 to 71,350 million fibers per liter
• Main results:
  • The tiles were produced at a Norwegian cement plant, and chrysotile made up 92 percent of the material
  • Whole cohort: 140 cancer cases observed versus 134.2 expected
  • Whole cohort, cancer of the digestive tract as a whole: SIR 129 (42 observed vs. 32.52 expected, 95 percent CI 93-175); no statistically significant excess for any digestive-tract cancer
  • Men with 20 years or more since first exposure: stomach cancer SIR 241 based on 11 cases (4.57 expected in Table 2), 95 percent CI 120-431, statistically significant
  • Men with 15 years or more of employment after the tiles were installed: stomach cancer SIR 161 (8 observed vs. 4.96 expected, 95 percent CI 70-318)
  • No cases of malignant mesothelioma were observed; the expected number was 0.41, and 0.07 for peritoneal cancer
  • Total mortality in the cohort was significantly lower than expected: 424 observed deaths versus 454 expected
  • In a separate group of lighthouse keepers who retired before 1960, before the tiles were installed (excluded from this study), 8 stomach cancer cases were found versus 3.7 expected
• The authors' conclusion: The authors concluded that the exceptionally large numbers of fibers measured in the tap water at some lighthouses might increase the risk of gastrointestinal cancers, but that this was difficult to explore because exact exposure data were lacking and diet was a confounding factor
• Limitations the authors state:
  • The study population was small and it is not known when erosion of the tiles started
  • Without knowing when the tiles began to deteriorate, the data could not be analyzed by start of asbestos exposure
  • The excess of stomach cancer may possibly be explained by diet, since the keepers lacked refrigeration until the late 1960s and early 1970s
  • Choosing which population rates to use for expected numbers is a methodological problem in this type of study

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Latency, Stomach Cancer, Standardized Incidence Ratio (SIR), confidence interval, Mesothelioma, Confounding.

Related studies

• Cancer of the gastrointestinal tract and exposure to asbestos in drinking water among lighthouse keepers (Norway) — K. Kjaerheim, B. Ulvestad, et al. (2005)
• Is there a risk to health in using asbestos--cement pipes for the carriage of drinking water? — S.F. McCullagh (1980)
• Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota — B.S. Levy, E. Sigurdson, et al. (1976)
• 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 incidence following exposure to drinking water with asbestos leachate — H.L. Howe, P.E. Wolfgang, et al. (1989)
• Cancer incidence and asbestos in drinking water, Town of Woodstock, New York, 1980-1998 — M.L. Browne, D. Varadarajulu, et al. (2005)

Browse more research in American Journal of Epidemiology, or return to medical research.