Aloha Sports Chiropractic

Aloha Logo (2)

How Does Chlorine Work As A Disinfectant?

For over 100 years, the safety of drinking water has been attributed to the addition of chlorine. This simple element does act like a disinfectant and can kill bacteria and viruses; many older studies stated that our drinking waters were safe because chlorine had lowered the risk of waterborne infections. Globally chlorine is widely used by most municipalities to disinfect the water. In addition chlorine has routinely been added to waters in spas, swimming pools and sauna. But now scientists are questioning its real benefits.

How does chlorine work as a disinfectant?

Chlorine when added to water reacts with organic matter like decaying leaves. This results in the generation of chemicals known as trihalomethanes which then act as disinfectants. The amount of trihalomethanes in the water depends on the season, source of water and amount of organic material present. Levels of trihalomethanes are generally low in large lakes but high in rivers, because they often contain more organic material.

How much Chlorine is in my water?

The majority of drinking water supplies in the nation have chlorine added to the water. Currently the guidelines recommend 4 parts per million of chlorine. However, it is not unusual for chlorine levels to be much higher depending on the season and environmental conditions Diabetes. In fact during the summer, many pools and beaches will be closed when the chlorine levels are over 4 ppm.

The benefits of chlorine

All the benefits of chlorine have been based on studies done several decades ago. The people who advocate chlorine in the drinking water claim that it is safe and works like an effective disinfectant. More important, they claim that chlorine works against all types of microorganisms including, fungi, viruses, and bacteria.

Whats the deal with chlorination?

But now there is newer evidence suggesting that chlorine may be more harmful to humans than previously thought. It is believed that the trihalomethanes generate free radicals and cause cell damage that eventually leads to cancer. While the EPA continually states that chlorine kills microorganisms, Dr Robert Carlson from the University of Minnesota states that this element also “destroys and damages normal cells in the body.” Chlorine is not selective in causing damage says Dr Carlson and ultimately it will lead to permanent damage.

The Chicken Study

In a remarkable study conducted by Dr Joseph Price, chickens were observed from birth to maturity; and one group was given water with chlorine and the other group plain water. The chickens given chlorine water were found to have poor survivability, constant shivering, reduced level of activity and signs of illness. At autopsy, these chickens had some degree of atherosclerosis in almost every blood vessel. In comparison the chickens not given chlorine thrived and grew bigger more rapidly. The results of this study have been widely quoted in the poultry industry and if chlorine can do this much damage to chickens, then one wonders what it can do to humans?

Cancer and Chlorine

There is major concern that any chemical used to disinfectant water can form by products that can be reactive and harm human health. Thus, there is now a public outcry against use of all chemicals in drinking water. Recent studies show that the  risk of cancer in people who drink chlorinated water is at least 93% higher compared to those whose water lacks chlorine. Laboratory studies reveal that high levels of trihalomethanes can cause various types of cancer, esp. bladder cancer. Many experts now believe that the chlorine in drinking water is similar to the air pollution. More data seem to suggest that chlorine seems to be a major cause of many health problems. Even  breast cancer has now been linked to chlorine. One study from Connecticut revealed that chlorine and its byproducts were found in high amounts in women with breast cancer compared to women without breast cancer.

Besides cancer there are now reports that trihalomethanes may also adversely affect pregnancy and induce miscarriage, cause eczema and changes in behavior.

What is the government doing about chlorine?

So far the government has not done much regarding chlorine in our drinking water. The Environmental Protection agency states that the present levels of trihalomethanes are very low and safe. However, with the vast number of recent data indicating that trihalomethanes can be toxic even at low doses, the EPA is now taking a look at all the date before making a recommendation.


Because of the worry that chlorine may not be safe, many cities have now turned to ozone to disinfect their waters. Unlike chlorine, ozonation does not produce trihalomethanes. However, the downside to ozone is that it is prohibitively expensive. Several other chemicals also have disinfectant activity like chloramine and chlorine dioxide, but again these are weaker agents and their long-term toxicity is not known.

What can the public do to minimize risk?

There is no easy way to get around chlorine in the drinking water. In fact, most bottled water also contains some amount of chlorine. The best and most effective method is to use activated carbon filters that can remove most of the chlorine from the home drinking water. There are several types of these filters and with all of them one has to rigidly follow the manufacturer’s guidelines. Plus, it is important to get your home water checked periodically for trihalomethanes to ensure that the levels are not very high.


1. Villanueva CM, Gracia-Lavedan E, Bosetti C, Righi E, Molina AJ, Martín V, Boldo E, Aragonés N, Perez-Gomez B, Pollan M, Gomez Acebo I, Altzibar JM, Jiménez Zabala A, Ardanaz E, Peiró R, Tardón A, Chirlaque MD, Tavani A, Polesel J, Serraino D, Pisa F, Castaño-Vinyals G, Espinosa A, Espejo-Herrera N, Palau M, Moreno V, La Vecchia C, Aggazzotti G, Nieuwenhuijsen MJ, Kogevinas M.  Colorectal Cancer and Long-Term Exposure to Trihalomethanes in Drinking Water: A Multicenter Case-Control Study in Spain and Italy.  Environ Health Perspect. 2016 Jul 6.

2. El-Tawil AM. Colorectal cancers and chlorinated water.  World J Gastrointest Oncol. 2016 Apr 15;8(4):402-9.

3. Valdivia-Garcia M, Weir P, Frogbrook Z, Graham DW, Werner D.  Climatic, Geographic and Operational Determinants of Trihalomethanes (THMs) in Drinking Water Systems.  Sci Rep. 2016 Oct 20;6:35027.

4. Kogevinas M, Bustamante M, Gracia-Lavedán E, Ballester F, Cordier S, Costet N, Espinosa A, Grazuleviciene R, Danileviciute A, Ibarluzea J, Karadanelli M, Krasner S, Patelarou E, Stephanou E, Tardón A, Toledano MB, Wright J, Villanueva CM, Nieuwenhuijsen M.  Drinking Water Disinfection By-products, Genetic Polymorphisms, and Birth Outcomes in a European Mother-Child Cohort Study.  Epidemiology. 2016 Nov;27(6):903-11.

5. Carlson, R.

6. Scientific American. Tapped Out?: Are Chlorine’s Beneficial Effects in Drinking Water Offset by Its Links to Cancer?

7. Price. J.M. Coronaries, cholesterol chlorine.

Recent Blogs

Leave A Comment

Appointment Type Selection

Please select the type of appointment you would like to schedule:

Weekend Clinic
Now Open

On call chiropractic services now available for cash only emergency patients. Additional $25 fee
Dr. Craig Eymann

Musculoskeletal Injury Specialist

Dr. Craig Eymann

Musculoskeletal Injury Specialist

Payment Options

Will you be using insurance for your visit?

Note for Insurance Patients

Select insurance provider and enter policy details. Providing insurance information allows us to verify coverage and confirm your appointment time.