The world’s greatest ever solution to disease? A toxic chemical worthy of something from Dante’s fevered imagination? The original Weapon of Mass Destruction? Chlorine is a versatile element – its story ranges from bleaching paper and clothes to water purification to trench warfare and environmental disasters such as dioxin poisoning. It’s not really whiter than white….
As a young secondary school chemistry student I witnessed a case of chlorine gassing – in the classroom. It wasn’t that the teacher deliberately gassed my friend, young Bill – it was self-inflicted by Bill himself more or less. We had just had a demonstration of how to make chlorine gas from scratch. I can’t remember the precise method now but it probably involved producing chlorine by mixing manganese dioxide and concentrated hydrochloric acid. The chlorine gas which is supposed to be green-coloured was collected in a ‘gas jar’. To keep the gas in order to experiment on it and protect us from its ravages the freshly made chlorine gas was sealed in with a glass lid sealed by Vaseline petroleum jelly. Precisely the same stuff you would have used on a baby’s bottom back in those days before the advent of Sudocrem and its ilk for treatment of ‘ammoniacal dermatitis’ or nappy rash. But I digress.
Our bright chemistry teacher decided that the whole of his first year chemistry class needed to recognise the smell of chlorine when they were exposed to it. This was back in the days of ‘touchy feely’ chemistry you see when you recognised compounds by their look and feel and smell. The suggestion that cyanide smells of bitter almonds, for example, always made me wonder who was the one to smell it and impart the information before keeling over like the spy caught by the enemy faced with no choice but to chomp on his handy cyanide capsule.
Teacher passed the gas jar full of the fresh chlorine around for each pupil to get a whiff of the gas, this strange alien-looking green gas which had just been produced on the lab bench in front of our eyes. You delicately slid the glass lid back on its airtight Vaseline seal enough to let a little bit waft out and then you sniffed it – carefully. Most of us gently wafted the aroma of ‘swimming pool’ towards our nostrils with our fingers waving above the jar.
At this kind of close range the smell of chlorine is much, much purer than the vaguely disguised chlorine you smell in and around a swimming pool complex – it is much more astringent, if that is the right word. With a gas jar beneath your nose right in front of you, you sure don’t forget the piercing smell of even the most delicate, gentle wafting of chlorine as it enters your nostrils.
But the bould young Bill did not waft it gently towards him, he stuck his shnozzle right into the jar and sniffed it in strongly. It was as if he were snorting a line of cocaine or that, while suffering from a bad cold, he was sniffing a rose trying to catch a very elusive and delicate scent. Bill quickly began to look green about the gills and passed out right there in the classroom. An ambulance was called and he was carted off to hospital to spend the best part of a week in an oxygen tent. Lucky for the teacher and lucky for Bill too, of course, he lived to tell the tale. Effectively he had received a chlorine gas dose close to the lethal dose that killed so many soldiers fighting in the trenches in the World War I.
By the same token if you drink a litre or two of disinfected water from the tap and you will imbibe a legally required residual amount of chlorine gas perhaps a milligram or two depending on how far you are from the water works. Perhaps sufficient chlorine to kill a family of mice if it was in the atmosphere and not the water? The lethal concentration for rats exposed is 293 part per million in one hour – i.e. in an hour half the rats exposed to 293 ppm chlorine in air will die. The desired concentration in drinking water is a hundred to a thousand times less than this. It is also dissolved in water so it is less harmful in your intestines than as a free gas attacking, say, the lining of the lungs of a soldier sitting in a WW1 trench.
Chlorine does react with organic matter in water, however, and produces by products such as chloroform and carbon tetrachloride which are definitely carcinogenic. The trick is to chlorinate water that has as little organic matter as possible in it – e.g. by using aluminium or iron salts to clean it up first. Unfortunately in some small group water schemes that don’t have iron or aluminium treatment facilities operators have been known to add more chlorine when the water goes brown or peaty after rain in order to bleach it. In such cases the amount of carcinogens coming out of the tap supply will well exceed all EU limits for nasties such as dissolved carbon tetrachloride (smell of rotten cabbage) and chloroform (gas used once used by dentists to knock you out).
On the other hand what if we did away with chlorine in our drinking water? What then? Undoubtedly we’d immediately be much worse off unless we had something to replace it with. Drink a litre or two of non-chlorinated non-disinfected water and you run a very high chance of imbibing a nice little colony of bacteria, viruses or some nasty protozoan parasite. Typhoid, cholera and all those gasteroenteric diseases prevalent before the discovery of public sanitation would be rife without the disinfecting action of chlorine. Some public health specialists laud chlorine as the single biggest lifesaver known to modern man. Much more important than antibiotics or modern surgical techniques in that it is used to prevent disease outbreaks which would otherwise occur on a routine and massive scale. Of course chlorine doesn’t solve all our problems. Cryptosporidium in particular is resistant. There have been a number of Irish outbreaks of Cryptosporidium (which usually originates from cattle slurry) and ‘boil notices’ from county councils seem to be increasingly common. Mullingar and Ennis come to mind in the last few years. In these cases chlorination is inadequate to kill the parasite. It’s immune to chlorine and requires extremely careful pollution control to eliminate the bovine source – cowshit entering into the drinking water system in other words.
Chlorine is of course an essential component of our own makeup with each person on the planet containing something of the order to 1.2 grammes of chlorine per kilogram body weight. We need it particularly to make the hydrochloric acid in our stomachs required for digestion. If the world’s population is something like 6.5 billion and the average person weighs, say 45 kg, then this means that the human population itself contains something over 350,000 tonnes of chlorine. This is the kind of useless fact that you can amuse or amaze your colleagues and friends with at coffee time tomorrow!
Many plastics and pesticides contain chlorine as a key element of their makeup. PVC, for example, is short for PolyVinyl Chloride. DDT the infamous insecticide, which accumulates in our fatty tissues, but nowadays banned pretty much everywhere around the globe, has quite a bit of chlorine in it too. Chlorofluorocarbons – those enemies of the ozone layer - have chlorine as also does dioxin a highly toxic cancer causing compound.
The production of dioxin when e.g. chlorinated plastics are burned is a temperature dependent process. The lower the temperature of the burn the more likely you are to get dioxins produced. In a well-designed and well-run incinerator that amount of dioxin produced is minimal – much less than that produced by backyard fires and motor car exhausts. If things go wrong and the burn temperature drops that is a different matter of course. In the USA the main route into the body is the eating of beef and dairy produce. Luckily in Ireland dioxin levels in milk and beef are much lower than many other industrialised countries. We clock in at one sixth the levels found in Belgium, less than one third of UK milk dioxin concentrations and half to one third of those found in France, Germany and the Netherlands.
The use of chlorine as a bleaching agent is well known to anyone who watches TV adverts for products such as Domestos. Cleaning, bleaching disinfecting all known germs and all at one go! The use of chlorine to bleach baby’s nappies or cloth for the making of T-shirts, or to whiten up that ream of paper you are loading into your printer or photocopier is another big use for chlorine. An interesting side effect of the use of bleach in toilets is the effective disabling of septic tank systems. This is because, like it says on the pack, chlorine is a pretty effective way of killing all known bugs. It can’t distinguish between good bugs and bad bugs though. Thus, killing the bugs that are needed to break down your toilet waste effectively knocks your septic tank out of action. Down there at the end of your garden it could perhaps be a highly efficient means of digesting down your toilet waste if the bugs that undertake this task were left alone long enough to deal with the ‘business’ to hand (using the word business advisedly). The punctuated flushing of large volumes of chlorine-based bleach/disinfectant down the loo, however, puts paid to that possibility. As a result your septic tank stinks to high heaven and annoys the neighbours and probably pollutes the groundwater even worse than it would if left to its own devices.
Should chlorine be banned completely? This is a non-argument because it’s not possible to simply ban the ninth (or eleventh depending on the source you read) most abundant element in the Earth’s crust outright as it will keep popping up regardless. There's a lot of chlorine in the sea as sodium chloride. But certainly there’s a case for eliminating or substituting chlorine in many industrial processes and day to day materials especially those we are likely to burn and produce dioxins in the process. But we need to change our attitudes – it is only when you begin to accept that it is okay to have something less than ‘white’ paper being stacked into your photocopying machine or printer that we can begin to reduce the amount of chlorine floating around the environment. The chlorine industry of course screams blue murder because plastics and paper together account for about half the modern production of industrial chlorine. They screamed over the ban on chlorofluorcarbons too but somehow the world has managed to struggle on without CFC cans of hairspray.
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