Alarming study – water chlorination may Increase cancer risk

Swedish scientists have published a study highlighting the risks associated with drinking tap water in Europe and the USA. According to their findings, water chlorination, at levels used in developed countries, increases the likelihood of developing bladder cancer by 33% and colorectal cancer by 15%.

Widespread Water Chlorination – Pros and Cons

Chlorine was first used to disinfect water in Kent, UK, in 1897 as a response to a local typhoid fever outbreak. By the early 20th century, chlorination of drinking water had become a common practice, significantly reducing the prevalence of serious diseases such as typhoid, dysentery, cholera, and hepatitis A. The method is inexpensive, widely available, and highly effective, and its adoption has greatly extended life expectancy in Europe and North America.

However, water chlorination has a major drawback – chlorine reacts with organic compounds present in natural water sources, producing hundreds of toxic byproducts known as trihalomethanes (THMs). The most common THMs – chloroform, bromoform, bromodichloromethane, and dibromochloromethane –have been shown to be carcinogenic in rats. This phenomenon was discovered in the 1970s, leading to the establishment of drinking water safety standards, which are currently set at 80 μg/l in the USA and 100 μg/l in Europe.

Dangerous Levels of THMs

Swedish scientists aimed to examine the link between water chlorination and the risk of developing certain cancers in adults. To do this, they analyzed over 2,000 scientific sources and identified 29 publications related to the presence of THMs in drinking water and cancer incidence in human populations. The meta-analysis focused on bladder and colorectal cancers, which are considered the most strongly linked to the chlorination process. The exact mechanism by which trihalomethanes (THMs) primarily affect these organs remains unclear.

Final conclusions were drawn from studies involving over 90,000 individuals. Groups exposed to the highest levels of THMs had up to a 33% greater chance of developing bladder cancer, with the correlation being stronger in men. Males were also found to be more susceptible to colorectal cancer, with a 15% increased risk associated with consuming water high in trihalomethanes.

It is important to note that, according to Swedish scientists, the risk of cancer increases at THM levels as low as 40 μg/l, which is significantly below current safety standards. The Environmental Working Group (EWG) suggests that the safe level of these toxic compounds in drinking water is just 0.15 μg/l, more than 600 times lower than the limits currently enforced in Europe.

Does Water Chlorination Have a Future?

The latest research findings challenge the validity of contemporary water treatment methods. Alternative solutions, such as UV disinfection or advanced filtration systems, remain too expensive for widespread implementation.

The concentration of trihalomethanes (THMs) in municipal water supplies is strongly dependent on the source – levels tend to be higher in surface waters than in groundwater, as surface waters contain more organic matter. To reduce toxic compound levels, it may be advisable to introduce pre-filtration methods to remove microorganisms and organic matter before disinfection.

The debate on setting new water chlorination standards remains open – a balance must be struck between minimizing cancer risks and ensuring microbiological safety in drinking water.

According to Emilie Helte from the Karolinska Institute in Stockholm, consumers should not stop drinking tap water, but it is recommended to use activated carbon filters at home, as they effectively reduce THM levels and other contaminants.