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I am attempting to research the results of case studies regarding polytetrafluoroethylene [PTFE] (commercially known as Teflon). More specifically I am attempting to make sense of this Abstract on Acute pulmonary effects of ultrafine particles in rats and mice. Not being a chemist I'm having a hard time understanding the results and hoping someone can explain in laymens terms. More specifically, the abstract mentions;

We used ultrafine Teflon (polytetrafluoroethylene [PTFE]*) fumes (count median diameter [CMD] approximately 18 nm) generated by heating Teflon in a tube furnace to 486 degrees C to evaluate principles of ultrafine particle toxicity that might be helpful in understanding potential effects of ambient ultrafine particles. Teflon fumes at ultrafine particle concentrations of approximately 50 micrograms/m3 are extremely toxic to rats when inhaled for only 15 minutes.

That seems straight forward enough. They heated up Teflon in a tube, and made rats inhale it, who subsequently died. Then it goes on to say;

We found that neither the ultrafine Teflon particles alone when generated in argon nor the Teflon fume gas-phase constituents when generated in air were toxic after 25 minutes of exposure. Only the combination of both phases when generated in air caused high toxicity, suggesting the existence of either radicals on the particle surface or a carrier mechanism of the ultrafine particles for adsorbed gas-phase compounds.

This is the part thats unclear to me. The Teflon particles alone, I think means the compound before they heat it, but what is the 'fume gas-phase when generated in air'? How is that different then the fumes they made the rats inhale (from which they died after 15 minutes)? What does the 'combination of both phases when generated in air' mean?

Aging of the fresh Teflon fumes for 3.5 minutes led to a predicted coagulation resulting in particles greater than 100 nm that no longer caused toxicity in exposed animals.

How would coagulation affect the toxicity of the fumes? Does it change the chemical structure of what the animals inhale somehow making it less toxic? Naturally speaking, I would assume 'more' particles would result in higher levels of toxicity, not less.

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    $\begingroup$ Perhaps better on the Bio stack? Particle size, accompanying toxic gases, any number of things impact uptake and impact. $\endgroup$ – Jon Custer Mar 5 at 16:38
  • $\begingroup$ Im asking for an explanation of mostly chemistry related terms. Not about the actual impact on mice. $\endgroup$ – n00b Mar 5 at 20:16
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I think the authors' choice of words might have confused you a bit.

We found that neither the ultrafine Teflon particles alone when generated in argon nor the Teflon fume gas-phase constituents when generated in air were toxic after 25 minutes of exposure.

What the authors mean is that when they used only ultrafine Teflon particles on the rats it did not kill them, nor did the Teflon fume gas-phase constituents when the rats were breathing that air for 25 minutes.

Only the combination of both phases when generated in air caused high toxicity, suggesting the existence of either radicals on the particle surface or a carrier mechanism of the ultrafine particles for adsorbed gas-phase compounds.

The individual substances, that is, ultrafine Teflon particles and Teflon fume gas-phase constituents were non-toxic for the rats. When the two were combined together in the air and the rats were made to breathe in that air was the point that they died, meaning that when these substances were combined in the air, some radicals$^{[1]}$ were being produced or some form of carrier mechanism was taking place.

The Teflon particles alone, I think means the compound before they heat it.

No, they meant that the ultrafine Teflon particles after heating. Alone meant these Teflon particles, by themselves, are not toxic.

what is the 'fume gas-phase when generated in air'

Gas-phase is simply a way of referring to the gaseous physical state. See here$^{[2]}$ for the definition. The phrase fume gas-phase refers to the fumes that the author observed on heating the Teflon to the temperature at which it turned into gaseous phase (phase is the word for referring to the physical state of a substance) while producing fumes.

How would coagulation affect the toxicity of the fumes? Does it change the chemical structure of what the animals inhale somehow making it less toxic? Naturally speaking, I would assume 'more' particles would result in higher levels of toxicity, not less.

Its not about more or less here. After some time, coagulation takes place causing the Teflon to take a solid form in the whichever utensil the researchers were using. What they mean by the coagulated Teflon being non-toxic is that in whichever way they made the animals (they have not specified which animal though) ingest it, it did not kill them. The quantity of the Teflon, the form in which it was ingested and by which animal was it ingested has not been specified, at least I couldn't find any clear reference in the abstract and I don't know how to access the full paper.

References:-

  1. IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook.
  2. IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook.
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  • $\begingroup$ I see you're edit quite a bit, but you're only making superficial edits, while editing new questions is for deciding if they are gonna get closed, and possibly deleted, or no. So edit should either substantially improve q. or may be a problem as it may interfere with reviewing. chemistry.meta.stackexchange.com/questions/3689/… You can also ask in chat if in doubt chat.stackexchange.com/rooms/3229/the-periodic-table $\endgroup$ – Mithoron Mar 6 at 13:45
  • $\begingroup$ @Mithoron I really appreciate the help mate. I'll improve :) Thanks for reaching out. $\endgroup$ – user79161 Mar 6 at 15:48

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