Type of disinfectant in drinking water and patterns of mortality in Massachusetts.

Abstract

Chlorination has been the major strategy for disinfection of drinking water in the United States. Concern about the potential health effects of the reaction by-products of chlorine has prompted use of alternative strategies. One such method is chloramination, a treatment process that does not appear to have carcinogenic by-products, but may have less potent biocidal activity than chlorination.We examined the patterns of mortality of residents in Massachusetts who died between 1969 and 1983 and lived in communities using drinking water that was disinfected either by chlorine or chloramine.Comparison of type of disinfectant among 51,645 cases of deaths due to selected cancer sites and 214,988 controls who died from cardiovascular, cerebrovascular, or pulmonary disease, or from lymphatic cancer showed small variation in the patterns of mortality. Bladder cancer was moderately associated with residence at death in a chlorinated community (mortality odds ratio = 1.7, 95% confidence interval = 1.3-2.2) in a logistic regression analysis using controls who died from lymphatic cancer. A slight excess of deaths from pneumonia and influenza was observed in communities whose residents drank chloraminated water compared to residents from chlorinated communities, as well as to all Massachusetts residents (standardized mortality ratio = 118, 95% confidence interval = 116-120 for chloraminated communities, and standardized mortality ratio = 98, 95% confidence interval = 95-100 for chlorinated communities).These results are intended to be preliminary and crude descriptions of the relationship under study. The serious potential for misclassification of exposure status and errors in death certificate classification of cause of death affect the interpretability of the overall evidence that patterns of mortality are similar according to disinfectant in drinking water.

Fluid intake and risk of bladder and other cancers

“…Several case-control studies supported an association between consumption of water from public sources and increased risk of bladder cancer. Some studies found that tap water with chlorine-and hence containing chlorination byproducts-may increase the risk of bladder cancer (Wilkins & Comstock, 1981;Gottlieb & Carr, 1982;Zierlier et al, 1986Zierlier et al, , 1988Cantor et al, 1987Cantor et al, , 1998McGeehin et al, 1993;Koivusalo et al, 1994;King & Marrett, 1996;Kiemeney & Schoenberg, 1996;Freedman et al, 1997). Arsenic in drinking water has also been associated with increased risk of bladder cancer (Chen et al, 1986(Chen et al, , 1992Wu et al, 1989;Bates et al, 1995;Hopenhayn-Rich et al, 1996;Chiou et al 2001), but it is unclear whether the levels of arsenic in drinking water from developed countries have any meaningful effect.…”

Deadly occupations: Assessing tuberculosis and accidental mortality among male workers in Sydney and Glace Bay, Nova Scotia, 1909–1917

“…Miettinen and Wang (1981: 147) liken the analysis of the mortality odds ratio to a type of case-control study, noting "the totality of deaths from the cause of interest, combining the exposed and nonexposed domains, can be thought of as a case series; and all the 'other' deaths can be thought of as a reference series for the cases-if exposure is not a risk indicator for death from those 'other' causes." Adopting a multivariate approach to analysis using logistic regression, researchers can then compare the odds ratios for a particular cause of death or disease cluster with reference to a particular risk factor (or "exposure") of interest, while also controlling for other confounding variables (see, for example, Burke and Sawchuk 2003;Lee et al 2003;Wray et al 2008;Zaridze et al 2009;Zierler et al 1986). When assessing mortality odds ratios, the entire study is conditioned on dying (i.e., all those individuals included in the analysis have died).…”

Meta-analysis of studies on individual consumption of chlorinated drinking water and bladder cancer

“…The study by Freedman was considered in an alternative analysis. Death certificate based case-control studies, [18][19][20] although have been frequently quoted, were not included in this meta-analysis because exposure information was either ecological or based on interviews of proxies…”