h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Our world today i littered with dangerous chemicals.
Our governments seem to be trying to protect us - for instance by banning medicines that have not been round long enough.
One substance we all have in every part of our daily lives is PTFE - one of its commercial names is Teflon - this if heated on an ordinary stove long enough, produces among other substances 2 gases which are in the chemical weapons convention section 2. On Du ponts own website it says it must not be heated over 260 degrees centigrade and yet from my research temperatures capable of producing these gases are reached on an ordinary stove in less than five minutes.
From reading the internet it kills pet birds very quickly if overheated, and makes users sick if inhaled after overheating.
yet it seems that ptfe is a major ingridient in fireworks - they reach these temperatures in seconds.
This year there have been major bird dye offs in villages and cities seemingly after the new year and christmas when masses of fireworks were let off.
Du pont have been fined tens of millions of dollars for environmental pollution, for not revealing to its workers that the chemicals used in its production were mutagenic and carcionogenic, and paid out vast sums in compensation for those effected.
(Its all on the net)
I live in Norway - i cannot buy dental floss here which is not coated with ptfe.
it is in water pipes, it is sprayed on aeroplanes, it is in cosmetics now, so why is no one worried, why are our governments not trying to ban its use?
Perhaps my information is wrong?
Perhaps we have so many similarly dangerous substances that no one worries?
Can anyone explain please?

I'd imagine part of the reason is you'd have to heat it to emit the gasses. To be honest, if you've something in your mouth, or on your face, if it gets hot enough to emit the gas, the tiny amount given off is going to be a tiny worry in comparison to the fact your head is almost certainly on fire.

As a sensible answer, it's always a balancing act. PTFE is an amazingly useful compound. It makes lives better for millions, if not billions of people every day. Counterbalancing that, there's a tiny risk that it will get hot enough, bearing in mind the temperature it would need to attain is hundreds of degrees outside it's normal use, except possibly in cookware, where it's only scores of degrees out. There's also the cost to consider of developing an alternative which is (a) cheaper and cleaner to manufacture and use and (b) safer.

I would say your information is sensationalist and scaremongering certainly, if not wrong.

The (unnamed) toxic gases released in the manufacture of teflon are only ever going to be of worry to those in its large scale manufacture. The amount you generate in your kitchen is not likely to be significant enough to harm a fly, let alone yourself.

Teflon is extremely inert so even at such elevated temperatures it will only break down slowly. It won't breakdown significantly over geological timescales at room temperature (I may be exaggerating for effect here ) so your dental floss remains perfectly safe to use.

Did you know there are measurable levels of carcinogens in burnt toast? Yet how is it that toast is not banned?
Doseage.

Yes, PTFE contains something that is a constituent of a chemical weapon. That is why companies who make PTFE have controls over amounts they can keep and how it is kept. Twiggy can explain more when he arrives.

Of course, there are chemicals everywhere that could be harmful to people but it is all controlled by regulating authorities.

Although one of the main chemical killers of people is not regulated at all...read and be afraid...be very afraid...

http://www.dhmo.org/facts.html#SYMPTOMS

Yes, I heard recently there were high levels of that in the water supply.

try mixing different cleaning products in the same toilet bowl, sooner or later you'll pull off weapons grade chlorine

OK, full disclosure upfront: I'm a chartered chemical engineer with fifteen years in industry, the last five and a half on the only PTFE manufacturing plant in the UK.

I make this fact known for two reasons. First, to allow you to make a judgement as to how much credence you may give my input, given that it is the very basis of my professional life and has been for half a decade. Second, to allow you to make that judgement on the basis that given what I've just said about myself above, you could narrow down the field of who I might be and who I might work for to a field of precisely one, and therefore I shall be duly circumspect in what I shall say.

Before we get on to the main question, what is this?

"Our governments seem to be trying to protect us - for instance by banning medicines that have not been round long enough"

What is this a reference to?

Anyhoo...

PTFE is a long, long chain of carbons, each with two fluorines attached. These fluorines don't quite fit neatly together, so the chain is a bit twisted. PTFE undergoes two phase transitions around room temperature, around fifteen and nineteen degrees centigrade, as the polymer chain stretches slightly and the fluorines rearrange themselves. This is harmless.

I don't know what Dupont's website says, but the figure of 260 C is very, very low indeed. What I do know is that PTFE is sold as having a viable working temperature of up to 300 degrees, and every day we sinter granular PTFE (heat it to adjust its physical properties) at about 400 C. PTFE only starts to unzip (i.e. thermally degrade) above 420 degrees. It's possible some gas may be given off at a lower temperature, but I've not seen anything which suggests this is a problem (i.e. I've seen websites that say things like "studies show...", but they never link to those studies.)

Now, some speculation: there *may* be an undesirable phase transition which occurs at 260 degrees which reduces the PTFE's water repellent and/or non-stick properties. It may be this which Dupont's advice refers to. Speculation ends.

There is an important caveat with PTFE, something everyone who works on our site is briefed about - polymer flu. When exposed to high temperature, PTFE does break down into harmful gases which, if inhaled directly, can cause flu-like symptoms for a short period (about 24 hours). The most common cause of polymer flu is getting particles of PTFE on your hands (VERY easy on our factory - despite its "non-stick" reputation, PTFE readily sticks to skin and clothing), transferring those particles from your hands to a cigarette, then smoking the cigarette. The tip of a cigarette can be anything from 500 to 700 C (five hundred to seven hundred, yes!), so plenty to break down the PTFE, and of course you then directly inhale the breakdown products.

The "chemical weapon" material you refer to is perfluoroisobutene, PFiB. Only very, very small amounts of this material, if any, would be produced by the breakdown of PTFE at high temperature. We make it, unavoidably, when we make TFE (it's an undesired byproduct of the reaction that makes TFE). The TFE for polymerisation has to be ultra-pure, so the PFiB and all the other byproducts must be distilled off. The PFiB and other high-boiling components are collected and incinerated. The process of collection and destruction is closely monitored, and at regular intervals UN weapons inspectors audit our factory.

It should be noted that birds have very, very sensitive pulmonary systems - it is for this reason canaries were used in mines to detect methane. Birds will be badly affected long before levels dangerous or even noticeable to humans are reached.

I'm not aware of PTFE being an ingredient in fireworks. I can't imagine why it would be. It has many undesirable properties for a firework material - it's heavy (twice as dense as water), a boring colour (white), and it doesn't burn. It does have incredibly good heat and chemical resistance, however, but it has one really terrible quality for a firework ingredient - it's expensive. But I'm not an expert on fireworks, so I'm going to leave that there.

Dupont have indeed been fined, several years ago, mainly for things related to the release into the environment of a surfactant vital to PTFE manufacture, ammonium perfluorooctanoate. No harmful effects on humans have been proven (and I say this calmly, knowing I have a slightly elevated level of this stuff in my blood), but it is biologically persistent (i.e. once it's in you it stays in you for years) and ubiquitous (i.e. it's been found everywhere, e.g. polar bear blood, and every molecule of it in the environment is there because of PTFE manufacturing processes). As a result of these difficulties, the entire PTFE industry, i.e. Dupont AND all its competitors, have agreed with the US environmental protection agency to phase out the use of this surfactant altogether. Projects related to this transition are a large part of my work, and represent significant costs to our business.

Nobody is worried about PTFE because it is, more than most chemicals you'll come into contact with every day, safe. If you were to swallow 3cm diameter disc of PTFE 1cm thick, it would pass through the concentrated acid and other vicissitudes of your digestive tract entirely unscathed. Please do not ask me how I know this. PTFE is uniquely inert - almost nothing we know of reacts with it *at all*. It is used all the time in all sorts of industries, at high and very low temperatures with corrosive, acidic, caustic materials. It is incredibly electrically resistive. It stays flexible even in liquid helium. It is, bar none and by far, the single weirdest substance I have ever been privileged to work with (and it's got some pretty stiff competition, let me tell you...).

You could swallow your entire roll of dental floss without ill effect. I would far rather drink water from a PTFE lined pipe than from one made of copper or even Bod forbid lead. Feed water through a pipe made of any metal, and some of that metal will leach into the water. Not much, but enough (if it's lead) to make you ill in the long term. Feed water down a pipe lined with PTFE, and what comes out is what went in, nothing more, nothing less.

Governments are not trying to ban its use because it's one of the most incredibly useful substances ever invented. Its incredible electrical resistance allows you to use it to insulate wire with a much thinner layer than you'd need of any normal plastic. This cuts space and weight, both of which are at a premium in aeroplanes and spacecraft. It is incredibly resistant to heat and chemical attack, meaning if you want to pump hot acid, you can line a pipe with it and stop worrying. It's ridiculously water-repellent, but it forms fibrils when you stretch it - so you can make a membrane which won't let liquid water through, but which water vapour will pass through. It's called Goretex, and it's made of PTFE. There are literally thousands of uses of this stuff, before you've got to non-stick pans and thread seal tape.

If you want to worry about a dangerous chemical in your house, look at bleach. Horrible, horrible stuff. Look in your medicine drawer - paracetamol can shut down your liver with really quite a small dose. Look at vegetable oil - nasty stuff if you leave it on the heat, far more directly dangerous than PTFE, even if you could get your non-stick pan hot enough. (I just did a back-of-an-envelope calculation - your average non-stick pan contains 0.0000000076 grammes of PTFE. How much gas can that realistically give off, do you think?)

Back to dangerous stuff in your kitchen... Look at vodka - toxic and highly flammable, and you keep bottles of it lying around. Look, for that matter, at custard powder. 3Dots and I passed an entertaining evening in our youth building a custard powder flame thrower.

In summary - I have far more to worry about than you do, since I make the stuff for a living (well, I design and install the plants that make the stuff...). And I don't worry. I'm far, far more careful not to burn my toast, to avoid fatty foods, to eat porridge every day to lower my cholesterol and to drink alcohol in moderation.

I hope that helps you relax and take a more realistic view of the risks.

"" Look, for that matter, at custard powder. 3Dots and I passed an entertaining evening in our youth building a custard powder flame thrower.""

look at banbury!! there used to be a custard powder factory in banbury, untill it exploded, cause, custard powder and a spark!!!

BOOM!!!

"3Dots and I passed an entertaining evening in our youth building a custard powder flame thrower."

Can you tell me how? I knew custard powder is explosive, but a flame thrower as well?

dead

wild stab in the dark here

get a blue/powder fire extinguisher, empty out the powder, carefully as it has a laxative effect!!!!

fill it with custard powder??

rig up some sort of ignition device??????

zippo on a stick with sticky tape

pull the pin, hit the red button, light the zippo, squeeze the trigger, hope it does not blow up in your face!!!!

So, how exactly did you find out the powder is a laxative?

during fire training we were told to avoid inhaleing it as it has a slight laxative effect, obviously some fire fighters found out the hard way and for their sacrefice in the intersts of research, we thank them!!


you can also have fun with the old 2 part cream/foam extinguishers

you had 2 components that had to be mixed with water to produce foam

1 you put in the bowl of a toilet, the other you put in the cistern

then wait for someone to flush the toilet

Thank you Twiggster for an extremely informative reply. This is one of the things I love about h2g2 - where else would you find such a wide range of subjects, ranging from simply silly to dead serious?

Bertie



What form of PTFE was this? I too am a chemical engineer as probably worked out from Twiggers custard comment(tho I could be an electrical engineer - more to come on that).

PTFE and it's many subtely different forms (PFA) are used in pharma productino due to it inertness and high temperature resistance. Very corrisive nasty chemicals are used pharma production (obviously fully removed before selling) it's the only way to make the stuff that means a lot of us aren;t dead yet. PTFE is the main flourocarbon used to line equipment used in processing pharma products along with glass and various types of stainless steel.

The main reason it's so darn good. The temperature of 260DegC is fine for pretty much any chemical reaction and hence that will be the main reason why DuPont will give that temperature. Over time the temperature cycling will have an effect on how the PTFE lines/sits with the normally metal outcasing of piping and equipment.



The carcinogen that is seen in burnt toast and lots of other cooked, charred foodstuffs is Acrlyamide which is a possible cause of cancer in some people.



The custard flame-thrower.

Number of ways of doing this but one is to get a bicycle pump, an electrical generator or chunky battery from a mate in electrical engineering ar such like. Electrical cable. Basically, run the isolated cable from the generator along the body of the pump, attaching it as you. Peel back the plastic casing at the end and bend over in front of the hole on the pump. suck up custard powder, turn on generator which heats up end of wire and push pump in to ignite the powder. That's a way of doing it.

Or just get a pump with custard poweder in it and fire it across the top of a candle...

Do you know, I'm not sure I'd want to be holding either of those!

>>The carcinogen that is seen in burnt toast and lots of other cooked, charred foodstuffs is Acrlyamide which is a possible cause of cancer in some people.<<

Actually I was referring to N-nitrosoamines but I'll go with acrylamide if that's in there too.

http://en.wikipedia.org/wiki/Nitrosamine

Probably the most deadly carcinogen in terms of deaths caused is oxygen.
Look up oxidative stress in google and

Yeah. Beware fresh air, it'll kill you.
eventually.

I once saw a box of rat poison that proudly proclaimed "Contains no Chemicals". It was surprisingly heavy.

I once had an argument with my rather stupid stepmother who was insisting that 'chemicals' only meant poisonous artificial substances. Therefore we couldn't talk about the 'chemicals' in the lovely organic food that she had cooked.

http://www2.dupont.com/Teflon/en_US/products/safety/index.html

"The U.S. Food and Drug Administration (FDA) has found Teflon® nonstick coatings acceptable for conventional kitchen use."

And the FDA are well known for cutting people's knackers off just for filling in paperwork wrongly...

OK, that's NOT true (I made that up before their lawyers come after me) but they do take this kind of thing almost that seriously.

If the FDA are OK with it so am I (See FDA lawyers...I think your client is doing a great job ).