Understanding the danger of chlorine in drinking water: Health risks
Among the various methods of disinfecting tap water, chlorine has held a prominent place for many decades. Its effectiveness, low cost, and ease of use have made it an essential tool for large-scale water treatment.
However, the use of chlorine is not without its questions. Concerns arise regarding the formation of disinfection by-products, potentially harmful to public health, and the emergence of resistant microorganisms.
In this article, we will explore the risks associated with the presence of chlorine in drinking water.
Why is chlorine found in drinking water?
Chlorine is present in drinking water for one essential reason: disinfection. It is a powerful disinfectant that eliminates harmful microorganisms, such as bacteria, viruses, and protozoa, which can cause serious diseases in humans.
What is the composition of chlorinated water?
The chlorine found in drinking water is not pure chlorine, but rather a compound derived from chlorine. It easily dissolves in water and readily combines with other particles, notably sodium, to form sodium chloride (table salt). Therefore, most chlorine is found in salty waters and soils in the form of rock salts.
That said, there are two main ways to add chlorine to drinking water:
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Sodium hypochlorite (NaClO): This is the most common form of chlorine used for water disinfection. It is also sometimes referred to as bleach or chlorine water.
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Hypochlorous acid (HOCl): It is the active form of chlorine that is responsible for disinfection. Sodium hypochlorite dissolves in water to form hypochlorous acid, the proportion of which depends on the pH of the water.
So, technically, chlorinated water is obtained by dissolving a chlorine-based compound (such as sodium hypochlorite) in water. This process then produces hypochlorous acid, which acts as a disinfectant.
How does chlorine act to eliminate bacteria and viruses?
The effectiveness of chlorine in tap water relies on the following mechanisms:
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Attack on cell walls: As an oxidizing agent, chlorine disrupts the structure of the cell membrane, causing it to rupture and the cell to die.
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Denaturation of proteins essential for the functioning of microbial cells: By altering the structure and function of these proteins, chlorine renders microorganisms unable to survive and reproduce.
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Disruption of metabolic processes: Chlorination disrupts the cell's ability to produce energy and synthesize essential cellular components, leading to its death.
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Oxidation of the nucleic acids (DNA and RNA) of microorganisms: By damaging their genetic material, chlorine can prevent the replication and reproduction of cells.
It should be noted that the presence of organic matter in water can reduce the effectiveness of chlorine, by consuming it or forming less active chlorinated compounds. Thus, for it to be effective, disinfection must be carried out on good quality water.
Similarly, the action of chlorine to eliminate bacteria and viruses depends on several factors, such as:
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a sufficient contact time,
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a slightly acidic environment (pH 6.5-7.5),
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higher temperatures,
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a sufficient chlorine level.
Advantages of using chlorine compared to other methods
If chlorine is a widely preferred disinfectant compared to other methods, such as ultraviolet light, boiling, ozone, etc., it is because it has the following advantages:
Effectiveness against pathogens
Chlorine eliminates a wide range of microorganisms, including bacteria, viruses, and protozoa, responsible for serious diseases such as dysentery, cholera, and typhoid. This differentiates it from filtration, which is more suited for removing suspended particles but does not destroy all microorganisms.
The rapid action of chlorine also allows for quick decontamination of water, which is particularly important in emergency situations.
Unlike some disinfectants (such as ultraviolet light), chlorination has a residual effect. In other words, the substance continues to kill microorganisms in the water even after its addition, ensuring lasting protection.
Ease of use
The chlorination process is relatively simpler to implement, unlike other methods such as ozone, and does not require complex infrastructure.
This makes it particularly suitable for rural communities and emergency situations where more sophisticated treatment solutions may be difficult to implement.
Good cost-effectiveness
The low cost of chlorine allows for the treatment of large quantities of water in an affordable manner, thus contributing to the improvement of public health on a large scale.
What are the health risks associated with the presence of chlorine in water?
Despite its many advantages, chlorine cannot eliminate all microorganisms, particularly certain protozoan parasites. This is one of many reasons why it is not recommended to drink tap water. Indeed, chlorination does not fully purify the water and does not remove other contaminants such as chemicals or heavy metals.
Similarly, prolonged use of chlorine can lead to the formation of potentially harmful by-products. This raises questions about the health risks associated with chlorine in tap water.
Here are some of its potential effects:
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Cancer: The formation of chlorinated disinfection by-products (THMs and haloforms) during chlorination could be linked to an increased risk of certain cancers, such as bladder cancer.
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Heart diseases: Cell damage caused by free radicals, induced by THMs, could play a role in the development of heart diseases.
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Premature aging: Chlorine could accelerate the aging process by damaging cells and promoting plaque formation in the arteries.
Thus, it is crucial to be aware of the limitations of chlorine and to combine it with other water treatment measures when necessary, to ensure safe and quality drinking water.
What are the alternatives to chlorine for water disinfection?
Aside from chlorine, there are other more or less effective solutions for disinfecting water. Here are a few.
Boiling
For centuries, boiling water has been a common practice to make it potable and safe for consumption. When water is heated to 100°C, it reaches its boiling point. At this temperature, the heat kills all harmful microorganisms, including bacteria, viruses, and parasites, that can cause serious illnesses.
Even brief boiling is sufficient to eliminate most pathogens. In general, it is recommended to boil water for one minute at low altitude and for three minutes at high altitude, where the boiling temperature is lower.
It is a method accessible to everyone, even in areas where access to treated drinking water is limited. However, boiling can alter the taste, color, and smell of the water, especially if it is very dirty. Similarly, it does not eliminate all chemical contaminants present in the water, such as heavy metals or nitrates.
Ozone disinfection
The World Health Organization (WHO) has classified ozone as a top-notch disinfectant, highlighting its superior effectiveness compared to other common treatment agents like sodium hypochlorite.
This chemical element acts quickly and leaves no residue, unlike some disinfectants that may persist in the water after treatment. Thanks to its properties, this substance naturally decomposes into oxygen, leaving no harmful by-products that could pollute the water.
Furthermore, ozone effectively removes compounds responsible for unpleasant odors and colors in water, thereby improving its organoleptic quality. However, its instability limits its disinfecting action over time and requires continuous production or repeated injection into the water to be treated.
Ultraviolet disinfection
Ultraviolet (UV) disinfection, also known as UVC disinfection, is established as an effective and environmentally friendly water and air treatment method. Its principle is based on the use of short-wavelength UV light (253.7 nm) to disinfect water without altering its taste or odor.
When microorganisms are exposed to this UV light, the rays penetrate their cell membrane and nucleus. They then damage their DNA or RNA, rendering them unable to reproduce or function, leading to their death. This method promotes a sterilization rate of up to 99.99%.
However, UV disinfection is not effective against certain protozoan parasites such as Cryptosporidium and Giardia cysts, which can cause severe diarrheal diseases. The presence of suspended matter or turbidity in the water can also reduce its effectiveness by attenuating the penetration of UV rays.
Depending on the quality of the water, other treatment steps, such as filtration or chlorination, may therefore be necessary in addition to UV disinfection.
Reverse osmosis
Reverse osmosis proves particularly useful for desalination, that is, the transformation of seawater or brackish water into drinking water.
It is an increasingly widespread filtration and disinfection method, often surpassing other techniques due to its efficiency and versatility. Its use extends to pure water barrels, community, domestic, and industrial drinking water, and many other areas.
The principle of reverse osmosis is based on applying a pressure greater than the osmotic pressure of the raw water solution on a semi-permeable membrane. This membrane acts as a selective filter, allowing pure water to pass while retaining impurities such as dissolved salts, microorganisms, colloids, and organic matter.
Reverse osmosis can remove more than 90% of dissolved salts and over 99% of microorganisms and organic matter present in water. One of the main limitations is that installing a reverse osmosis system requires a significant initial investment, including:
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semi-permeable membranes,
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high-pressure pumps,
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pre-treatment systems,
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control equipment.
Microfiltration
Microfiltration relies on a simple mechanism: retaining particles larger than the filter's pores and removing them from the water to be filtered. However, viruses (average size of 0.03 μm) are generally too small to be retained by ceramic microfilters (pores of 0.2 μm), unless they are clustered together.
Some filters incorporate complementary agents, such as activated carbon. The latter improves the taste and smell of water by retaining organic or inorganic residues, such as pesticides that end up in tap water after a long journey. However, it does not have a bactericidal action. Thus, microfiltration requires disinfection using a complementary product.
How to reduce exposure to chlorine?
It is possible to reduce exposure to the danger of chlorine in drinking water by using home water filtration systems and adopting good practices on a daily basis.
Home water filtration systems to remove chlorine from tap water
Home water filtration systems offer many benefits, ranging from healthier and tastier water to better health protection. Different types of home water filters are available, including:
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Tap filters
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Under-sink filters
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Water filters for coffee machines
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Gravity water filtration systems.
At Weeplow, our gravity water filtration systems contain activated carbon. Its effectiveness lies in its ability to adsorb a wide range of contaminants (Chloride, heavy metals, eternal pollutants known as PFAS, etc.), thus improving water quality.
Practical tips to reduce chlorine ingestion on a daily basis
In addition to using a home water filtration system, here are some common practices to help you reduce chlorine ingestion on a daily basis to ensure your health safety:
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The adsorption capacity of activated carbon is saturated after a certain period of use, so you must regularly replace the filter according to the manufacturer's instructions to maintain its effectiveness.
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In the absence of a filter, consider boiling tap water for one minute to eliminate gaseous chlorine. However, this does not eliminate other potential contaminants.
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Opt for filtered water for everyday consumption, especially for preparing hot drinks and food (especially pasta, rice, and vegetables).
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Replace the habit of drinking directly from the tap with using a glass or a bottle filled with filtered water.
Stay safe from the dangers of chlorine in drinking water with the right habits!
Chlorine is a practical and effective substance for disinfecting drinking water and protecting it from harmful microorganisms. However, it can also pose risks to health and the environment.
There are many alternatives to chlorine for disinfecting tap water. However, they are often more expensive and more difficult to implement.
That is why the ideal is to take measures to reduce your exposure to chlorine in tap water. Filtered water is among the most accessible solutions. Browse our shop to find the gravity water filtration system that best suits your needs.
Frequently Asked Questions
What are the current regulations regarding the use of chlorine in drinking water and the acceptable levels of chlorination by-products?
Specific chlorination requirements may vary from one region to another, depending on local or national legislation. The Council of the European Union requests that the concentration of chlorine in drinking water does not exceed national chlorine limits before consumption. In France, this is a minimum of 0.3 mg/L of free chlorine at the outlet of treatment plants and a minimum of 0.1 mg/L of free chlorine at any point in the water networks.
Chlorine has a characteristic bitter and metallic taste that can be easily detected, even at low concentrations. This can mask the subtle natural flavors present in water, such as minerality or freshness. Furthermore, the reaction of chlorine with organic matter present in water can produce volatile chlorinated compounds, which contribute to an unpleasant odor.
What is the environmental impact of using chlorine in water treatment?
Chlorine production requires energy and can generate polluting by-products. The transport and storage of this chemical element are also likely to pose risks to safety and the environment in the event of an accident. Indeed, chlorine leaks or discharges of chlorinated water may contaminate soils, transforming into other compounds, such as methyl chloride, a powerful greenhouse gas.
