An investigation of the use of asbestos cement pipe for public water supply and the incidence of gastrointestinal cancer in Connecticut, 1935-1973

Our plain-English summary of An investigation of the use of asbestos cement pipe for public water supply and the incidence of gastrointestinal cancer in Connecticut, 1935-1973, by J.M. Harrington, G.F. Craun, J.W. Meigs, et al (American Journal of Epidemiology, 1978).

The study

• Authors: J.M. Harrington, G.F. Craun, J.W. Meigs, P.J. Landrigan, J.T. Flannery, R.S. Woodhull
• Journal: American Journal of Epidemiology
• Published: 1978;107(2):96-103
• Cited by: 38 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. 001085).

Abstract

The age adjusted sex specific incidence data for stomach, colon, and rectal cancer for Connecticut townships for the period 1935 to 1973 were used to investigate whether asbestos cement pipe usage for domestic drinking water is associated with gastrointestinal cancer. The townships were grouped according to the Assessment of Exposure (AOE) and Risk Factor (RF) for asbestos. These are composite indices of asbestos exposure including factors relating to the age of the pipe, the ability of water to leach asbestos from the pipe, and the length of pipes used by the population. No association was noted between these asbestos risk scores and gastrointestinal tumor incidence.

In plain English

This study asked whether carrying public drinking water through asbestos-cement pipe was associated with cancer of the stomach, colon or rectum in Connecticut. The authors compared each town's cancer cases from the Connecticut Tumor Registry for 1935 to 1973 with the numbers expected from statewide rates. Towns were grouped by population density and by whether they had asbestos-cement pipe. Exposure was scored using pipe length, population served, pipe age and how corrosive the water was. About 576,800 people in 82 towns were estimated to receive water through such pipe. In 19 tap-water samples, chrysotile counts ranged from below the detection limit (10,000 fibers per liter) to 700,000 fibers per liter. No obvious trends or patterns linked estimated exposure with cancer rates. In 1965-1973, the trend was, if anything, toward lower ratios of observed to expected cases in towns with the pipe than in other towns. The authors noted that town and water-system boundaries did not match and that employment and occupational exposure were unknown. They concluded that any effect was not obvious and that safety could not be proved or disproved.

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: Ecological study comparing town-level cancer incidence (observed versus expected cases) with town-level indices of exposure to asbestos-cement water pipe, plus electron microscopy water sampling
• Who was studied: Connecticut towns, with cancer incidence data by township for 1935 to 1973. Asbestos-cement pipe was used by 149 public water systems in 82 towns. About 576,800 people received water through it in 1975. Seven towns were omitted because their data were unsuitable.
• Exposure: Drinking water carried through asbestos-cement pipe in public water supplies. Exposure was scored with the Assessment of Exposure (AOE) index, built from pipe length, population served, pipe age and water aggressiveness. For the main comparisons, exposure was grouped only as present or absent. Water samples from the distribution system contained chrysotile fibers.
• Main results:
  • No obvious trends or patterns were found between estimated asbestos exposure from drinking water and observed/expected ratios for cancer of the colon, rectum or stomach.
  • In 1965-1973, the trend was, if anything, toward lower observed/expected ratios in towns with asbestos-cement pipe than in the other towns.
  • Observed/expected ratios tended to rise as town population density increased.
  • Rank correlation tests were run on 72 sets (three cancers, two sexes, four time periods, three density groups). The few significant correlations came before most asbestos-cement pipe was introduced and showed no pattern with its introduction.
  • In 19 water samples taken after the water had passed through asbestos-cement pipe, chrysotile counts ranged from below the detection limit (10,000 fibers per liter) to 700,000 fibers per liter.
  • Higher fiber counts were generally found in water supplies with an aggressiveness index of less than 10.
• The authors' conclusion: The authors concluded that if asbestos in water had influenced gastrointestinal cancer rates in Connecticut, the effects were not obvious. They also concluded that the safety of asbestos in water supplies could not be proved or disproved at that time.
• Limitations the authors state:
  • Water supply areas did not match town boundaries, so some residents of 'exposed' towns were not served by asbestos-cement pipe. The authors said this would dilute any positive association.
  • The authors had no information on place of employment or occupation. Occupational asbestos exposure could be far larger than exposure from water.
  • There was no information on the biological effects of fibers of the sizes found in drinking water, or on the effects of cooking.
  • Tumor data were less accurate in the early years of the registry, when up to 37 per cent of cases were diagnosed from death certificates alone.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Asbestos Exposure.

Related studies

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• Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota — B.S. Levy, E. Sigurdson, et al. (1976)
• Is there a risk to health in using asbestos--cement pipes for the carriage of drinking water? — S.F. McCullagh (1980)
• Cancer of the gastrointestinal tract and exposure to asbestos in drinking water among lighthouse keepers (Norway) — K. Kjaerheim, B. Ulvestad, et al. (2005)
• Degradation of asbestos - Reinforced water supply cement pipes after a long-term operation — J. Zavašnik, A. Šestan, et al. (2022)
• Epidemiology study of the use of asbestos-cement pipe for the distribution of drinking water in Escambia County, Florida — J.R. Millette, G.F. Craun, et al. (1983)

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