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In this article we examine what is Chlorine, its health benefits, possible toxicity and deficiency problems.

Chlorine Cl2) is a metal element in a yellow-greengaseous form. that is rarely found free in nature. The most common chemical compound of chlorine is sodium chloride – the salt we all know. Chlorine in its elemental form is essential for the normal functioning of the body.

When found in a soil chemical compound it is absorbed by the root of plants as anion (Cl) and is taken up by humans through the diet.

Chlorine Health Benefits

Chlorine is the first anion in the extracellular space, where, together with sodium, it acts as a key electrolyte regulating osmotic pressure and water balance in the body. Chlorine is also required for the synthesis of hydrochloric acid in the stomach.

It is essential in cases of indigestion and helpful in many stomach disorders.

Chlorine Deficiency

In cases of chlorine deficiency (hypochloremia), there is a decrease in muscle strength, teeth begin to be destroyed and the ability to digest the body’s food is reduced.

Patients with elevated chlorine levels (hyperchloremia) may experience weakness, rapid breathing, drowsiness and lethargy that may develop into coma.

A blood test for chlorine may be needed to screen patients who experience prolonged vomiting, diarrhea or weakness.

Daily chlorine intake

There is no Recommended Dietary Allowance for chlorine, but there is an adequate intake ranging from 1800 to 2300 mg per day, which can meet the needs of healthy adults.

A typical diet, more often than not, will exceed the body’s chlorine needs.

Bohr model of chlorine from Signal Garden

Dietary sources of chlorine intake

Chlorine is usually combined with sodium, creating sodium chloride as mentioned earlier. Therefore, common salt is the main source of chlorine intake.

In addition to salt, other chlorine-rich foods include asparagus, endive, butter, cucumber, fish, lentils, okra, milk, olives and tomatoes.

Disinfectant properties

  • Manufacturing industry – Chlorine is used in the manufacture of plastic (PVC), disinfectant solutions, solvents and bleaches – particularly in the paper industry. It is a disinfectant, six times more effective than iodine.
  • Antimicrobial – Clorine It is used for the inactivation – removal of microbes in homes, hospitals, swimming pools, catering areas, hotels and other public places.
  • Water disinfectant – It works by causing problems in the cell membrane of microbes or by affecting their DNA. It is the most widely used disinfectant for drinking water and wastewater worldwide. When dissolved in water, it produces hypochlorous acid (HOCl) and hydrochloric acid (HCl). Hypochlorous acid is quite active against micro-organisms. [1]
  • Inactivating Viruses – The effectiveness of chlorine in inactivating viruses is significant. In an experiment carried out on 20 virus species, the most sensitive virus to chlorine is a reovirus species that was 99,99 % inactivated within 2,7 minutes, while the most resistant is a poliovirus species that was 99,99 % inactivated after 60 minutes. [2]

Hypochlorous acid is particularly active in inactivating Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Shigella dysenteriae. [2]

In 1991, the Peruvian government decided to stop chlorinating water in swimming pools. This resulted in a cholera epidemic. It is estimated that about 1 million people were infected and 15,000 died. [3]

While chlorine is effective in inactivating bacteria, its extensive use has resulted in the gradual resistance of bacteria. [4]

Chlorine as disinfectant in drinking water

Chlorine is a chemical element that belongs to the halogen family. For many decades it has been added to drinking water as a disinfectant since it can kill many pathogenic microorganisms. Its use in water began in 1910 by the Jersey City Water Company in Jersey City, USA. This practice proved to be very effective against waterborne diseases such as cholera and typhus.

The use of chlorine as a disinfectant in drinking water should be subject to strict criteria and should be carried out in a scientifically and technologically appropriate manner, and with continuous monitoring.

Part of the chlorine in water reacts with various water constituents and is captured, while the remainder remains in the water as a residual quantity.

The residual (free) chlorine in drinking water should not exceed 0,5 mg/l at the beginning of the network and 0,2-0,3 mg/l at the most remote points of the network.

How chlorine can be removed from drinking water

The only solution to this problem is the installation of good certified activated carbon water filters. These filters can remove every trace of chlorine and its by-products from tap water.

Thus, you can safely consume clean filtered water without the unpleasant odour and especially without the danger of chlorine, provided that you follow the rules and replace your filter at the right time.

Water running from a tap
Water running from a tap

Chlorine Toxicity

In high doses chlorine is toxic and chronic exposure can cause health problems (liver damage, stomach irritation, contribution to arteriosclerosis, etc.).

Research has shown that some chlorination by-products are carcinogenic. [5]

Swimming in pools containing chlorine may increase the risk of cancer, according to a 2010 Spanish study. [6]

According to a 2015 US study, when eyes turn red after swimming in a pool, it is the swimmers’ urine, not chlorine, that is to blame.

Chlorine Origin – Action

When chlorine is dissolved in water it produces what is known as chloride water. A substance which disinfects due to the release of oxygen according to the reaction:

2Cl2 + 2H2O → 4HCl + O2

Chlorine is a strong oxidizing agent, capable of reacting with many organic and inorganic contaminants in water, including ammonia, proteins, amino acids, iron and manganese.

The amount of chlorine required to react with these substances is called the minimum chlorine demand. In addition to pH, other factors that affect the effectiveness of disinfection are temperature, time of effect and concentration.

It is liquid in its commercial form as sodium hypochlorite. In solid form it is the calcium hypochlorite. When added to water, a variety of chlorine compounds are formed. An example would be the reaction with ammonia resulting in the production of inorganic compounds known as chloramines.

Chlorine also reacts with organic materials resulting in carcinogenic compounds, trihalomethanes possibly chloroform, bromodichloromethane, bromoform and chlorodibromomethane.

Other chemical oxidants used for the disinfection of water supply networks are: potassium permanganate, hydrogen peroxide, chloramines, chlorine dioxide and ozone.

The forms of chlorine that can be added to water for disinfection are sodium hypochlorite (salt), hypochlorous acid and organic chlorine.

However, these compounds drastically change the pH downwards. They consequently make the water more acidic, thus corrosive and aggressive to steel and copper piping. For this reason they are rarely used in public water supply systems and more commonly in swimming pools and reservoirs.

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