[Stoves] particulate size retention

Thu May 24 21:55:04 CDT 2018

Thanks Andrew

Now we can understand why there is such controversy about the health impacts of nanoparticles.

Burning grass, as in veld fires, creates a huge amount of ultrafine PM. This has been going on for eons, literally. How much additional material like that is produced by, say, diesel engines, the cleanest of which produces hardly any detectable PM1 at all. It has been pointed out that the engines shift the PM from larger sizes into the range that has nearly no efficiency at being impacted in human lings. Diffusion, yes, and that applies to the nose, eyes, anything I suppose. 

Our lives are full of ultrafine particles. We should not be making precise claims for something we cannot even measure well, let alone characterise. Smoke is bad for you. Fine. Let's get on with deleting it. We don't have to create an inverted pyramid of wild guesses standing on that single point.

Crispin

-----Original Message-----
From: Stoves <stoves-bounces at lists.bioenergylists.org> On Behalf Of Andrew Heggie
Sent: Thursday, May 24, 2018 6:40 PM
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: [Stoves] particulate size retention

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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