Nitrates in Drinking Water and the Risk of Death from Rectal Cancer: Does Hardness in Drinking Water Matter?

Abstract

The objectives of this study were to (1) examine the relationship between nitrate levels in public water supplies and increased risk of death from rectal cancer and (2) determine whether calcium (Ca) and magnesium (Mg) levels in drinking water might modify the effects of nitrate on development of rectal cancer. A matched case-control study was used to investigate the relationship between the risk of death from rectal cancer and exposure to nitrate in drinking water in Taiwan. All rectal cancer deaths of Taiwan residents from 2003 through 2007 were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. Controls were deaths from other causes and were pair-matched to the cases by gender, year of birth, and year of death. Information on the levels of nitrate-nitrogen (NO(3)-N), Ca, and Mg in drinking water was collected from Taiwan Water Supply Corporation (TWSC). The municipality of residence for cancer cases and controls was presumed to be the source of the subject's NO(3)-N, Ca, and Mg exposure via drinking water. Relative to individuals whose NO(3)-N exposure level was <0.38 ppm, the adjusted odds ratio (OR) (95% CI) for rectal cancer occurrence was 1.15 (1.01-1.32) for individuals who resided in municipalities served by drinking water with a NO(3)-N exposure > or =0.38 ppm. There was no apparent evidence of an interaction between drinking water NO(3)-N levels with low Mg intake via drinking water. However, evidence of a significant interaction was noted between drinking-water NO(3)-N concentrations and Ca intake via drinking water. Our findings showed that the correlation between NO(3)-N exposure and risk of rectal cancer development was influenced by Ca in drinking water. This is the first study to report effect modification by Ca intake from drinking water on the association between NO(3)-N exposure and risk of rectal cancer occurrence. Increased knowledge of the mechanistic interaction between Ca and NO(3)-N in reducing rectal cancer risk will aid in public policymaking and setting threshold standards.

Multiple imputation for assessment of exposures to drinking water contaminants: Evaluation with the Atrazine Monitoring Program

“…Since the water quality measurements are relatively infrequent in a calendar year, epidemiological studies have generally averaged data across years and CWSs (Rinksy et al, 2012;Weyer et al, 2001) or restricted the study population to metropolitan areas served by a single CWS, with or without supplemental monitoring programs (Munger et al, 1997;Ochoa-Acuna et al, 2009;Chang et al, 2010). These approaches, however, have significant limitations that are particularly difficult to overcome in EPHT applications.…”

“…SDWIS data have been utilized in several epidemiological studies in the United States (Rinksy et al, 2012;Ochoa-Acuna et al, 2009;Ward et al, 2007;Weyer et al, 2001;Munger et al, 1997), and similar data have been used in other countries (Migeot et al, 2013;Chang et al, 2010;Villanueva et al, 2005). Since the water quality measurements are relatively infrequent in a calendar year, epidemiological studies have generally averaged data across years and CWSs (Rinksy et al, 2012;Weyer et al, 2001) or restricted the study population to metropolitan areas served by a single CWS, with or without supplemental monitoring programs (Munger et al, 1997;Ochoa-Acuna et al, 2009;Chang et al, 2010).…”