What is chlorine?
Chlorine, abbreviated as ‘Cl’ and with an atomic number of 17, is the twenty-first most common chemical element found on Earth. It is a yellow-green gas at room temperature. In fact, its name comes from the Greek word khloris which means ‘pale green’. It rarely occurs on its own in nature, but can be found everywhere in the form of chloride salts. Sodium chloride is the most common form which we usually refer to as plain old salt. It is essential to all forms of life and we find it all throughout the earth’s crust and our seawater. [1]
Why do we put chlorine in water?
Chlorine is the most common disinfectant when it comes to treating water, and water treatment facilities use it exclusively for disinfection before despatching the water to the population. They tend to deal with outbreaks of algae and other pathogens by adding more chlorine during the water treatment process so sometimes we get higher than usual doses of it in our tap water. This tends to happen during droughts, bushfires, floods and other extreme weather events.
Around 1 – 3.5 million people die each year from water contaminated with harmful bacteria such as E. coli, so chlorinating our municipal water supplies is absolutely necessary. Some parasites like cryptosporidium can survive being exposed to chlorine for more than ten days so our water authorities monitor for this one and will issue boil water alerts if and when it is detected. However, a good biological filter such as the EZEK EM-Medium or a reverse osmosis filter system will provide extra peace of mind. The usual symptoms of cryptosporidium infection are stomach cramps, diarrhoea, nausea and vomiting which can last from anything from several days to several weeks.
Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times.
Each individual bacterium is oblong shaped. Photo by Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU.
At high concentrations chlorine is extremely poisonous for all living organisms and it was even used as chemical warfare agent during World War I. However, at the levels used by water authorities to treat water for our taps, even when extra is added to deal with extreme weather events, it is completely safe to consume. Adding more chlorine is absolutely necessary at these times but that isn’t to say it’s not without its problems. It can sometimes make our water taste like water from a swimming pool and can leave our hair and skin after a shower feeling dry and powdery, but it is still safe to drink.
It is not technically possible to be allergic to chlorine but some people with sensitive skin can find it irritating and develop a rash when exposed to it. [2] While there are no specific warnings from doctors for babies or people with sensitive skin to avoid bathing with chlorinated water, a shower filter like the Alya Shower-Maid is a simple way to remove chlorine for a gentler showering experience. There are also claims from some sources that showering and flushing toilets can volatise chlorine into the air. While the levels will most likely be harmless to the skin, the claimers say that breathing in aerated chlorine can cause breathing difficulties for people with asthma and other respiratory illnesses, and may have ill effects over the long term. They therefore suggest de-chlorination prior to showering or bathing.
Does chlorine cause cancer?
No, this is a myth perpetuated by unscrupulous water filter suppliers and chlorine-free pool manufacturers. There is no evidence that chlorine can cause cancer. [3]
Water disinfection by-products, called trihalomethanes (THMs) can form when chlorine reacts with organic matter in the water, and these may have possible links with some cancers. However, the links are not well established or conclusive, and according to the Australian Drinking Water Guidelines: “the risk posed by disinfection by-products is considerably smaller than the risk posed by the presence of pathogenic microorganisms in water that has not been disinfected.” Water authorities strictly monitor for THMs according to the Australian Drinking Water Guidelines but they can also be reduced by aerating the water at the tap, allowing the water to stand, boiling the water or using an activated carbon filter which all i-LAN water filtration products contain. [4]
How do we test how much chlorine is in our water?
The easiest method is to buy some chlorine test strips from a hardware shop or a swimming pool supplier. These usually involve dipping the strip into the water and then waiting a period of time before comparing it to a colour chart. The closest match will determine the level of chlorine in the water. OTO drops are another common method for testing water for the presence of chlorine.
Using a pool chlorine indicator to test for chlorine gas escaping from a solution of acetic acid and sodium hypochlorite.
The Australian Drinking Water Guidelines allows for up to 5 mg of chlorine per litre in drinking water. In most cases the levels found are somewhere between 0.1 mg/L to 4.0 mg/L.
How do we remove chlorine from water?
Thankfully chlorine isn’t too difficult to remove from water. It’s a gas in its natural state at room temperature so it will evaporate out of the water if we leave it long enough. The other fact is that it’s a negatively charged ion, so if we pass it through a positively charged material, such as a granular activated carbon (GAC) filter found in all i-LAN water filtration products, the chlorine ions (and THMs) will stick to the filter and get left behind.
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One thing to be aware of is that chlorine will be absorbed by most organic material. A simple test to demonstrate this is to get some chlorine test strips and test a glass of water straight from the tap. If there’s chlorine in it (which we should hope there will be), the strip will react and change colour which you can then compare to the chart included with the package to determine the chlorine level. Then try the same test after putting your fingers or a vegetable in the water for a little while. You’ll notice the water will show little to no sign of chlorine then, which means it has been absorbed by your body or the food you were about to eat. If you don’t like that idea, always wash and/or cook your vegetables in filtered water. If you have a vegetable garden in your back yard, there’s also merit in irrigating it with filtered water or just use rain water.