R.O.C. # 220416
Bladder Cancer and
Chlorinated Water
National Bladder Cancer Study Shows Linkage.
By Annette Keen
Probability link has been demonstrated between chlorinated water exposure and bladder cancer, according to findings published by the Environmental Epidemiology Branch of the National Cancer Institute in Bethesda, Md. the researchers say that, having currently undeterred bias, the risk factor in developing bladder cancer among people who ingested chlorinated water range from 12 to 27 percent, with risk escalating among smokers. One of the researchers, Kenneth Cantor, Ph.D. of the National Cancer Institute tells Water Technology that the linkage is based on data gathered over a period of a year and a half in the late '70s. The National Bladder Cancer Study involved some 9000 people from all over the country about 3000 bladder cancer cases and 6000 noncancer cases. Since then, researchers continue to analyze and evaluate the database. Associations are seen between the level of tap water consumption and the incidence of bladder cancer. "When we grouped the people according to what their source of drinking water had been," Dr. Cantor explains, " the risk was much, much stronger among people who had been drinking chlorinated water for much of their lives, as contrasted to those who had been drinking nonchlorinated water. Dr. Cantor says that in fact, the people who had been drinking nonchlorinated water showed No increase in risk with the increase in volume of ingested tap Water, "Cancer risk increased with the amount of consumed water," he says, "but it was seen only in people who had been drinking chlorinated water most of their lives.
Dr. Cantor's conclusions have been published in the Journal of the National Cancer Institute.
Reason to Concern Several epidemiological studies have, during the past ten years, attempted to evaluate whether there is a link between chlorinated water ingestion and cancer. These studies were prompted by the widespread use of chlorine as a drinking water disinfectant and by the finding that carcinogenic substances, particularly the trihalomethanes, were formed in the drinking water because of chlorination. The suspected cancer sites have been the bladder, rectum, and colon. Many of these studies have been criticized for among other reasons, the potential for misclassifying exposure variables. With this in mind, the National Bladder Cancer Study considered 27 other risk factors for bladder cancer, along with chlorinated drinking water (see Table 1). Dr. Cantor says that the suspected carcinogenics lurking in chlorinated water are the trihalomethanes and the higher- molecular weight by-products.
Table 1
Risk Variables
- age
- sex
- years of education
- religious affiliation
- marital status
- coffee consumption
- hot tea consumption
- Iced tea consumption
- daily tap water consumption( Includes coffee, tea, tap water, and reconstituted juices)
- daily chlorinated tap water consumption
- daily nontap water consumption. (includes soft drinks fruit juice, milk wine, beer, and spirits)
- exposure to hazardous occupational materials
- farming occupation
- pack-years of cigarette smoking
- pipe smoking
- use of chewing tobacco
- use of snuff
- pelvic area irradiation as a medical treatment
- use of artificial sweeteners
- use of hair-coloring products
- positive family history of urinary cancer
- past history of diabetes mellitus
- history of bladder infection
- bladder stones
- history of kidney infection
- kidney stones
- urban density index
