<<Disclaimer: Verify this information before applying it to your situation.>>

I asked for a simple explanation for those of us who are not mathmatically inclined of ppm.  Here are some that I think are easy to understand.

Its either a weight or volume comparison.  Lets say there's a pile of stuff
that weighs one million grams.  If there is 1 ppm of gluten in it, then
there would be one gram of gluten in those million grams of stuff.  It could
also be volume.  If there were a million cubic millimeters of stuff, then
one cubic millimeter would be gluten, for that same 1 ppm.  Or perhaps if
there are a million molecules of stuff, then one molecule could be the
contaminant.  I think  ppm is flexible so that you use whatever measurement
is appropriate to the situation.  In surveying, they also use ppm to express
an allowable measurement error.  If a surveyor measures a million feet with
a GPS setup, he may say the measurement to within 10 feet, for 10 ppm, or
whatever.  Regardless, it's the ratio.  If you talk about 20 ppm, then for
every million units of stuff, there could be 20 units of gluten.

It's a real common measure of contamination.

You may have been asking for the way they measure the units for this gluten
debate.  If so, I don't know.  I think that's one of the points of
contention in this particular debate over the allowable levels of gluten.
The people who want a lower standard, lower than 20 ppm, are using some very
sophisticated chemical methods.  The industry is saying they can't even
measure less than 100 ppm, obviously using a much cheaper method.
-------------------------------------------------------------------------------------

Probably the best way I can explain is to use a comparison of marbles. And 
lets say the marbles are round as they should be, but there was a problem 
with the manufacturing and twenty of the one million marbles came out in a 
square shape. If you put all one million marbles in a big vat and mixed them 
up, then 20 ppm would represent the 20 square marbles that are in the mix.

So if you gave everyone a cup of marbles from the vat and twenty of them 
were square, most people would not get any square marbles in their cup, but 
some people would get one or two or potentially even more if they were 
unlucky with the mix. Or if we were not talking about marbles, but instead 
talking about powder, maybe everyone would get an ever so small amount of 
the bad 20.

I found this definition of ppm on the internet...
Parts per million ("ppm") denotes one particle of a given substance for 
every 999,999 other particles. This is roughly equivalent to one drop of ink 
in a 150 litre (40 gallon) drum of water, or one second per 280 hours (11 
days, 16 hours). One part equals 0.0001%.

Hope this helps.

Cheryl

Cecilia, TX


*Support summarization of posts, reply to the SENDER not the CELIAC List*
Archives are at: Http://Listserv.icors.org/SCRIPTS/WA-ICORS.EXE?LIST=CELIAC