The study, published in the April 15 issue of International Journal of Cancer, found high intake of tap water or tap water based drinks each day increased the risk of bladder cancer in men, reports foodconsumer.org.
For the study, researchers reviewed six previous case-control studies involving 2,749 bladder cancer cases and 5,150 cancer free controls, most of whom resided in the U.S., Canada or Finland. Some data were collected from subjects in France and Italy.
People consuming 2 liters of tap water per day were 50 percent more likely to have bladder cancer compared to those who consumed less than 0.5 liters per day, researchers found. The association was more significant in men than women.
Heavy consumption (defined as five cups or more a day) of coffee, which uses tap water, was also linked with an increased risk of bladder cancer. This was more significant among smokers.
Researchers noted, however, that drinking fluids other than tap water or tap water based drinks was not associated with bladder cancer risk.
Researchers suggested that the increased risk may be related to the cancer-causing contaminants in tap water such as disinfection by products among which trihalomethanes are the most prevalent resulting from chlorination.
But researchers found no evidence linking the increased risk of bladder cancer to the trihalomethane exposure.