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<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Dear Andrew,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoPlainText><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>« I'll take the liberty of reposting your question to Prof
Lloyd about how come the smallest particles are more likely to be exhaled
rather than absorbed through the lung membrane and his good explanation and
response »<o:p></o:p></span></i></p>
<p class=MsoPlainText><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Sure! Thanks!<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Dear Philip,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>OK, thanks for
the explanation.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Trying to learn
a little more on that, but that’s not so clear.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>This study here:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><a
href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5735549/">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5735549/</a>
<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>says<o:p></o:p></span></p>
<p class=MsoNormal>« Matter with a diameter of 10 µm or less is considered
suspended particulate matter, and matter with a diameter of 2.5 µm or less is
considered fine particulate matter. Ultrafine particles refer to particles of
100 nm or less; by their nature, these particles do not readily sediment or
flocculate, and thus have a longer retention time in the atmosphere than fine
particles allowing them to be carried long distances by the wind [<a
href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5735549/#b1-eht-32-e2017021"
id="__tag_655718834">1</a>,<a
href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5735549/#b2-eht-32-e2017021"
id="__tag_655568956">2</a>]. In terms of health hazards, fine particles are
only absorbed by alveolar macrophages when they enter the lungs, whereas
ultrafine particles are also absorbed by airway epithelial cells, which can
cause an inflammatory response in the airway. »<span style='font-size:
11.0pt;color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>This one talks
about really small ultrafine particles:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><a
href="https://arstechnica.com/science/2010/11/why-do-some-nanoparticles-get-trapped-in-our-lungs/">https://arstechnica.com/science/2010/11/why-do-some-nanoparticles-get-trapped-in-our-lungs/</a>
<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>« With
particles smaller than 34nm, surface properties began to matter. Positively
charged surfaces impeded the translocation of nanoparticles, while the negatively
charged, polar, and zwitterionic surfaces allowed translocation from lungs to
lymph nodes. The smallest zwitterionic particle (5nm) can be easily cleared
from the body. They moved from lungs to lymph nodes within three minutes and
into urine after just half an hour. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>The authors’
findings are helpful for drug design. For example, if you wanted to deliver
drugs quickly to the blood stream and allow unused drugs to be cleared via
urination, you would design nanoparticles to be around 5nm and avoid positively
charged surfaces. On the other hand, if you wanted the drugs to accumulate in
the lungs, you would design large or positively charged nanoparticles. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>The research
results also provide insight into nanoparticle toxicity. Pollutants that are
not positively charged and less than 34nm in diameter are fairly dangerous, as
they can easily traverse through the body. Particle diameters between 6nm and
34nm are possibly the most toxic, as they won’t be easily cleared from the
body; they could migrate around and accumulate in organs and tissues. <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>The authors’
results agree with a lot of the existing data that relate nanoparticle
properties with toxicity or therapeutic efficiency. »<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Submicron
particles indeed seem of the erratic kind.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Best,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><br>
Xavier<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-family:"Tahoma","sans-serif"'>De :</span></b><span
style='font-family:"Tahoma","sans-serif"'> Stoves
[mailto:stoves-bounces@lists.bioenergylists.org] <b>De la part de</b> Philip
Lloyd<br>
<b>Envoyé :</b> mardi 29 mai 2018 18:42<br>
<b>À :</b> 'Discussion of biomass cooking stoves'<br>
<b>Objet :</b> Re: [Stoves] ***SPAM*** Re: ***SPAM*** RE: Stoves Digest,
Vol 93, Issue 5<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;color:#1F497D'>It
is difficult conceptually to even think about the mechanism whereby submicron
particles interact with matter. I have suggested to you it is a question of
momentum. At the sub-micron scale “surfaces” are a moosh of electrons –
that’s all you can see as you approach the surface. You may be lucky, and
be riding a particle which is looking for an electron, but even so with that
excess of surface electrons you are likely to get repulsed. Alternatively you
may be going fast enough (Boltzmann allows it) to dash through the Coulomb
barrier. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;color:#1F497D'>These
probabilities are calculable and lead to low adsorption at less than 0.5
micron. I’ve given you a mechanistic, Newtonian interpretation, which is a good
enough first approximation. Being more exact gets fun but some of the approximations
you have to make are hairy.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;color:#1F497D'>Hope
that gives some clarity<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;color:#1F497D'>Philip<o:p></o:p></span></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:12.0pt;
font-family:"Times New Roman","serif"'><o:p> </o:p></span></p>
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