back to article The return of Killer Chlorine

After many mind-sapping years of trawling through the morass of health scare stories, I formulated a number of laws, one of which was the Law of Beneficial Developments: The intensity of the scaremongering attack on any new development is proportional to the level of benefit that it endows. Unbelievably, the Chlorine Scare has …


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Helmets - do you feel lucky

I had 2 notable crashes on bikes:

1st: cycling North from Castlebay on Barra (Outer Hebrides), when on coming minibus caused friend in front to brake, me looking at scenery, wildlife, etc, reacted too late and over the handlebars I went. Broken A-C joint and bike helmet in 2 parts held together by the staps, with a nice jagged rock pressed about 1/2" into one half. Painful shoulder (understatement) but no other injuries.

2nd: cycling in a bike race in Hamburg, Germany in a peloton of about100 riders, maybe at 40kph, some wheels touch in front, and down go the riders, I pick the gap I am to put the bike into but that develops into the person I am riding/falling over, a person a few riders behind me in a similar situation, his bike and pedal do a nice gouge up my back and into my helmet ripping it clean off, I have another destroyed helmet with a pedal embedded in it, that helmet was replaced by the manufacturer, who at that time wanted the damaged helmets as part of their R and D cycle, not sure if that is done today.

A 3rd incident worthy of note, a very close friend working on scaffolding a building site fell 2 metres (7 feet), eyewitnesses said he landed OK a little shocked and went to stand up a plank off the scaffolding also falling caught him squarely on the back of the head, he died instantly, his hard hat had fallen off during the fall, if the hat had remained on I am sure he would have climbed back up and carried on his job. He was 24 yo.

Helmets do work, and with my children, no helmet - no bike.


Hydrogen Hydroxide, and other responses.

I am saddened to see that nobody has pointed out that Dihydrogen Monoxide is more properly known as Hydrogen Hydroxide, and, is, in fact, quite beneficial when used properly: http://www.armory.com/~crisper/DHMO/.

Personally, I always put my bike helmet on before putting on the riding gloves, as the riding gloves impaired my dexterity a bit. But otherwise - the helmet saved me from a number of nasty bumps. It never saved my life - I never allowed myself to get into any situations in which my life was threatened in that manner. It was always very obvious to me, with the number of ventilation holes in it, that the bike helmet was not up to real impacts.

If people had been responsible in their use of DDT, none of its environmental effects would have been anywhere near the levels they were. For reference, I had an uncle who swore by DDT. He had one bucket of the stuff, which he had bought a couple years before it was banned. That bucket lasted him for many, many years (I seem to recall it finally ran out sometime around 1995.)

And, finally, to say something on-topic, the form of chlorine in tap water may be its most lethal form, but it's also the form found in your stomach. And, last I checked, my stomach has a higher concentration. If that's the case, I have a difficult time understanding how the chlorine in the tap water is going to hurt me. In any event, it tastes a bit nasty, and that's fixed by a little filtering. Of course, the statistics do play out: the number of people saved by chlorinated water is greater than the total number of people who suffer from any of the complications that have been adversely associated with its use (even including those people who would have those complications regardless, and even including those complications which are not, actually, related). If my previous statement is accurate, anyone who contests the use of chlorinated water on safety grounds is a moron.

Black Helicopters

@John Kale and Mr. Brignell

I have to wonder whether it was the researcher that caused the sensationalism in the chlorine scare. It looks like the original study was a data trawl designed to turn up items worth investigation. Someone in the researcher's organization (the media department, the Director or the researcher herself?) decided to alert the media that some interesting avenues for investigation had been identified, probably as part of a grant application cycle. It obviously snowballed from there into a meaningless mess of sensationalism. While there is a role for the media in documenting scientific research and making it meaningful to the general public, this study should never have been brought to the public media's attention.

And Mr. Brignell: while this was an interesting, thought-provoking article pointing out real flaws in the way the media handle statistics and science, I'm sorry to see you conflating the risks (or lack of risk) of ionic chlorine from salt with the Sodium Hypochlorite used in bleach and the TCH compounds that arise in drinking water. Don't fight junk science with junk science.



I live in the Netherlands, and as people know: lots of people riding bikes here and almost no one wears a helmet. As it is, most accidents involving cyclists are usually side impact from a car, and the helmet would not have helped. On the other hand, here we have a lot cycling paths (either free-laying or a reserved strip on the main road), which probably makes it a whole lot safer then in countries without a developed cycling-culture.

When I was in school I had to ride 30 km by bike daily (15km to school, and 15km back) and had some 'accidents' (linking of handlebars with the friend next to you, slippery roads, racing cyclists who don't yield). In my experience, you usually are able to break your fall and as a result are more likely to hurt your hands, arms or knees (or maybe your balls) then your head.

In my opinion the benefits of a bicycle helmet is grossly overrated (as almost all other Dutch seem to think), I only think they can have some benefit for:

1) kids: inexperience and small posture will make it easier for them to hit their head, and the helmet will probably not save more lives, but prevent them from crying (negative effect in the Netherlands: more likely to be bullied by other kids without helmets)

2) racing cyclists: racing in a large group of cyclists makes it more likely that you cannot anticipate and break your fall, or that someone in behind you drives over you

Silver badge

It's safest to not get vaccinated, as long as every one else is.

"And did you know that most children who get complications or die from whooping cough are too young to have been vaccinated"

And where did they get whooping cough from? The people who didn't get vaccinated.


Cycle safely

Ref. Cycle helmets.

There was a scientific study, I believe the researcher was based at Bath. He fitted a proximity sensor to his bicyle on his regular trip to work. He rode the bicycle with and without the helmet.

The cars came closer to him when he wore a helmet.

He was hit twice during the test, both times when wearing said helmet.

But: it doesn't mean it's better not to wear one. The risk of an incident may be slightly higher, but the consequences if you land on your head are many times more serious.

Dead Vulture

Hmmm ...good question, but -

Christine Houghton said: "Since its creation, chlorine has been a chemical catastrophe. It is either chlorine or us."

Chlorine. We're all going to die sometime ...

PS: Even the radioactive isotope version will outlive humanity by a long stretch. Its half-life is 301,000 (± 4,000 years).



"And where did they get whooping cough from? The people who didn't get vaccinated"

Or the people who did. My partner has post-polio syndrome, despite never having officially had the disease. Indeed, virtually all cases of polio in the Western world are caused by the vaccine, as it doesn't exist in the wild.

Curiously, deaths and complications from whooping cough in very young babies increased a while after vaccinations began. This was a bit of a mystery until it became apparent that mothers who had been vaccinated were unable to transfer their immunity (not being the same as that obtained from the actual disease) through breast-feeding. The same is true of measles, so none of this is quite as simple as it looks.

Also, look up shaken baby syndrome...


Bicycle helments

I used to cycle 25 miles each day, until I was given a free frlying lesson over an Audi TT.

Anyway, in ten years of cycling hard, I've fallen off the bike twice, and had the one nasty accident mentioned above, and you know what? Despite not wearing a helmet now, I'd much rather that if my head was going to scrape along the ground, I would like it to be covered.

Sure, I'm convinced that not wearing a helmet makes me a safer cyclist, but as a driver I don't notice if a cyclist is wearing a helmet or not; I go out of my way to pass considerately regardless.

So, in short: helmet makes scrapes less painful.


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bad science

I haven't seen so much bad science (on all sides of the argument) since the "Intentional Design" people last tried to argue that their hypothesis is actually a theory.


Fighting junk science with junk journalism

Reading the as "chlorination was stopped in Peru" referenced article (published by

the organisation of the US chemical industry), I've now read two articles from

people claiming to provide some scientific insight, but in fact just tell stories. "From a superior vantage point." And not even they are reported correcty.

To summarize "I was surprised to learn that some local PAHO officials were encountering pockets of resistance to chlorination from a number of health officials, both in Peru and in other countries" as "chlorination was stopped in Peru"

without any figures how widespread its adoptions was before and after the

cholera outbreak is probably just the ususal way, Greenpeace and other people

looking for attention do it.

To criticize the anti-industrial attitude of most of the ecological movement and put

the suffering of human beings at the center of the debate is absolutely reasonable,

but this kind of industry-hugging unwillingness to really climb on the " superior vantage point" is an insult to reason, even this is not the main point of the article.

I see: The Register bites the hands feeding IT, not chemistry.

If you want to read about science, read Science.


In defence of 0.05

I've had several scornful reactions from mathematicians when I have referred to 0.05 as the level of statistical significance commonly used in biology. "What about the law of large numbers?" they cry.

Well, yes, when you are looking at large numbers, a probability of 0.05 doesn't mean a hell of a lot. But a lot of the time in biology you are not dealing with large numbers. Sample sizes in the tens or hundreds are pretty typical. For those kind of sample sizes there is a whole branch of statistics which specifically deal with small samples - things like Student's t-test and so on. When you are doing that sort of thing, getting p < 0.05 generally does mean something significant.

Sadly, a lot of people in biology don't really understand what the stats are doing, so 0.05 gets treated as a magic number. Hey, I got p < 0.05, it must be true!

This is particularly true in epidemiology, which is one branch where sample sizes usually are large. Data trawling looking for correlations at p < 0.05 is just bad science.

It seems to me that this is another consequence of the dumbing down of science, and the insistence that all science has to be "applied". If you don't teach the theoretical underpinnings of pure science, then applied science is just bullshit.


Lies, damn lies and statistics

Good to see someone challenging this plethora of meaningless statistics, 68.25% of which are made up on the spot!


Oh, my...


"That would be the lethal strain of cannabis then..."

For some bizarre reason, my mind parsed this as the 'lethal strain of cannibals.'


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Reminds of a proposed road-safety measure - put an 8-inch steel spike in the centre of all car steering wheels. Drivers might then tend to be a bit more cautious.

Cycle helmets work in the opposite direction... see http://en.wikipedia.org/wiki/Risk_compensation (I haven't actually read this yet, I'm just hoping that it supports my position).


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RE: The Doctor, and the rare disease...

Right this is a long thread, so this hopefully won't get read....

There is this disease, that affects all people in equal proportion at a rate of 1 in 100 000. Assuming your a normalish human being, your chances of getting the disease is 1/100 000.

Now you go to the doctor for a routine check up (ie. the disease doesn't present any symptoms except sudden death) where he does a battery of tests. Guess what, the test comes back positive for sudden death disease.

"Lucky" for you, there is a cure, that is 100% effective, but which kills you if you don't have the disease. The doctor then tells you the test for the disease is 90% accurate. That is, if it says you don't have it, there is a 10% chance that you actually do, and if it says you don't, there is a 10% chance that actually you do.

Thus, the question is, what is the probability that you have the disease, given that the test was positive?

Applying Bayes' Theorem, hopefully correctly, gives:

(0.90*0.000 01)/(.9*0.000 01 + 0.1*0.999 9)

= 9 in 111 119 or roughly 0.0081%

or roughly 1 in 10 000.

So, no, don't take the "cure", except if your feeling really unlucky, who knows, you could be the 1 in 100 000 person who actually has the disease.




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