[Stoves] particulate size retention

Andrew Heggie aj.heggie at gmail.com
Thu May 24 17:40:03 CDT 2018


I find this an interesting  facet of the particulate  discussion so I have
changed the subject  as it referred to a whole digest and had plainly been
labelled as spam

Philip posted

"We measured retention of silica dust as a function of particle size. The
human filter scavenged everything above 10 micron very well. Between 10 &
2.5 there was degradation and increasing quantities were retained. Below
2.5 down to about 0.8 retention increased. Below about 0.6retention dropped
rapidly ,and was effectively nil from 0.3.
This was publshed back in about 1974, research by the gold mining industry
in Johannesburg."

Xavier posted


"Dear Philip,



OK, thanks for the precisions.

But don’t the recent studies found, or suspect, that below a certain size,
like below 0.1µ, retention increases since the nanoparticles cross the cell
membranes?

Not sure I understood right."

My inference from Prof Philip's post about the 1974 study was that the nose
effectively filtered out 10 micron and above, the particles from 10 microns
  down to 2.5 microns were filtered out to some extent but the remainder
entered the lungs and were retained. From 2.5 microns down to 0.8 microns a
higher proportion was retained in the lungs but particles below 0.3 microns
acted increasingly like gases and did not impact the lung membranes and
were thus largely exhaled.

I'm unsure which size and below would pass through the lung membranes and
enter the blood stream rather than remain in the lung, or indeed by what
mechanism the body could evict them.

The point as I understand it is >10microns don't get as far as the lung,
<10microns  but >2.5microns  some do get retained in lung but what happens
to them?

<2.5microns and >0.8microns  are increasingly retained in lung and most of
these will cross into the blood stream??. Less than 0.6 microns  and down
to 0.3 microns the percentage retained decreases again (but is this
particle numbers or mass?) Below 0.3 microns enter the lungs but get
exhaled so do not enter the body.

Andrew




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