Is it harmful the chlorine added to the drinking water?

Is it harmful the chlorine added to the drinking water?

Maybe you already know that the drinking water contains a certain amount of chlorine added at the time of making it drinkable; and maybe, you have also heard that the chlorine is a chemical compound that could be carcinogenic. Is that true? How harmful could be the chlorine to our health?

Chlorine has been used in water purification for years, specifically in the disinfection stage. Generally, it is present in drinking water in concentrations of 0.2 to 1.0 mg/L, and its purpose is to eliminate microorganisms that may be present in the water. The WHO (2006) established a reference value of 5mg/L, and says that at that concentration or less, no adverse effects have been observed in humans or animals that are related to the consumption of chlorine in drinking water.

Why do some people relate the chlorine as a carcinogenic substance? The real problem of chlorine comes due to the formation of subproducts such as trihalomethanes (THM) during the potabilization process. THM’s are considered carcinogenic compounds according the WHO (2006) and are formed in drinking water because of the chlorination of the organic matter present in the raw water.

For this reason, ozone is already being used in drinking water treatment plants in many countries, as an effective method to reduce the potential for THM’s formation. By using ozone, the elimination capacity of organic pollutants is improved, which reduces the possibility of THM’s formation in the chlorination phase. If you want more information about our ozone systems, contact us at

References: WHO (2006) Guías para la calidad del agua potable (recurso electrónico). Third edition in spanish. Link: