Trihalomethanes in drinking water and the risk of death from esophageal cancer: does hardness in drinking water matter?

摘要

Background: Chlorination is presently the most common procedure used for water treatment globally. Despite the effectiveness of chlorine in preventing morbidity and mortality due to waterborne pathogens, there remains concern regarding possible adverse health effects associated with chronic exposure to chlorination disinfection by-products present in drinking water. Aims: (1) to examine the relationship between total trihalomethanes (TTHM) levels in public water supplies and risk of esophageal cancer occurrence; (2) to determine whether calcium (Ca) and magnesium (Mg) levels in drinking water modify the effects of TTHM on risk to develop esophageal cancer. Methods: A matched case-control study was used to investigate the relationship between the risk of death attributed to esophageal cancer and exposure to TTHM in drinking water in Taiwan. Controls were selected randomly and were pair-matched by gender, year of birth, and year of death. Data on TTHM levels in drinking water were collected from Taiwan Environmental Protection Administration. Information on the levels of Ca and Mg in drinking water was obtained from the Taiwan Water Supply Corporation. Results: Relative to individuals whose TTHM exposure level ＜4.9 ppb, the adjusted OR with 95% CI for esophageal cancer was 1.02 (0.84-1.23) for individuals who resided in municipalities served by drinking water with a TTHM exposure ≥4.9 ppb. There was evidence of an interaction between drinking-water TTHM levels and low Ca and Mg intake. Conclusions: Our findings showed that the correlation between TTHM exposure and risk of esophageal cancer development was influenced by Ca and Mg levels in drinking water. This is the first study to report effect modification by Ca and Mg intake from drinking water on the correlation between TTHM exposure and risk of esophageal cancer occurrence. Increased knowledge of the interaction between Ca, Mg, and TTHM in reducing risk of esophageal cancer development will aid in public policymaking and standard setting for drinking water.