Link Between Chlorinated Water and Cancer Risk

In a previous article, “Let’s Have the Water Talk,” we investigated the common compounds found in municipal tap water, such as lead, fluoride, disinfectants, radioactive compounds, and pharmaceuticals. However, there is another noteworthy chemical that is commonly added to tap water: chlorine. For an undetermined reason, although the among of chlorine in tap water is small, people, generally, accept it as safe. Nevertheless, that is untrue. In this article, we will examine some of the consequences of drinking tap water as it concerns chlorine consumption as it related to increased cancer risks.

Increased Risk of Colorectal Cancer and Bladder Cancer

According to the American Cancer Society, in the United States, colorectal cancer is the third leading cause of cancer-related deaths in men and women, and the second most common cause of cancer deaths when men and women are combined [1]. Overall, the lifetime risk of developing colorectal cancer is about one in twenty-two (4.49%) in men and one in twenty-four (4.15%) in women [1].

Additionally, approximately 2.4% of men and women will be diagnosed with bladder cancer at some point in their lifetime, according to the National Cancer Institute [2].

Scientists have noticed an association between consuming chlorinated water and an increased risk of colorectal cancer.

This association was noted back on July 1, 1992, by the New York Times. In that day’s newspaper, the New York Times published an article entitled “Tiny Cancer Risk in Chlorinated Water” [3].

According to researchers at Harvard University and the Medical College of Wisconsin, chlorinated drinking water has been linked to small increases in the rates of rectal and bladder cancer, and this study was rather robust because researchers combined data from ten studies to limit the amount of error [4]. Further, the researchers noted that a population that consumes chlorinated drinking water has a 21% increased risk of developing bladder cancer and a 38% increased risk of developing rectal cancer [5, p. 962].

The researchers also attributed the increased risks to the prevalence of the cancers during 1992:

“If we posit that the association demonstrated between chlorination by-products and cancer represents a causal relationship in some way, the positive relative risks identified for bladder and colon cancer can best be interpreted in the context of attributable proportions (i.e., that portion of cases that can be attributed to a given risk factor32). By a conservative estimate, based on the 54% of the population that consumes chlorinated surface water (rather than the 75% that consumes chlorinated water), a 21% increase in the risk for bladder cancer and a 38% increase in the risk for rectal cancer translate into attributable proportions of 9% and 15%, respectively. With US incidence rates for bladder and rectal neoplasms [cancers] of 47,000 and 44,000 cases per year, respectively, these proportions suggest that about 4,200 cases (9%) of bladder cancer per year and 6,500 cases (18%) of rectal cancer per year are associated with the consumption of chlorinated water” [5, p. 962].

Now, the researcher’s estimated would be dramatically higher, since 98% of Americans drink chlorinated water and there are 80,470 and 145,600 new cases of bladder and colorectal cancer yearly, respectively [1] [6] [7].

The researchers concluded their study with saying, “these findings should provide an impetus to identify, develop, and implement disinfection strategies that are not associated with adverse health effects” [5, p. 962].

The researchers were also uneasy about publishing the paper, as noted by the New York Times. One reviewer of the article claimed, “were uneasy about informing people about this problem until some alternative was available” for fear that people would demand an end to chlorinating water [3].

Still, this was not the only study that noted this consequence of consuming chlorinated tap water.

In a 1997 study, researchers investigated the association of drinking chlorinated water with cancer incidence amount postmenopausal women in Iowa [8]. Again, the researchers found that there was an increased risk of colon cancer and all cancers combined [8].


Although studies have noted this negative correlation, the United States government has not removed chlorine and replaced it with a substitute. Hydrogen peroxide has been shown to destroy infectious organisms and impurities in water 4,000 times better than chlorine and ozone treatment be equally successful [9], and the United States government could quickly initiate a country-wide change. However, they seem to be silent on the topic.

As noted in “Let’s Have the Water Talk,” one of the best ways to dechlorinate drinking water is through a distillation system. If you are interested in purchasing a water distiller, Healthmasters offers several distillation systems, with the most popular being Water Distiller Model 3200.

If you have any questions about any of the distillation systems Healthmasters offers, please feel free to call our office at 800.726.1834.