Phyll > wrote:
>> Of the 30 items Ankit Lochan lists for analysis it would be impossible
>> (in the real world) to have zero presence for at least 29 of them -
>> then at what positive level of presence do you define 'pollution'?
>> And is your level the same as my level?
>
>Wouldn't the test show what a the upper limit is in ppm or other unit
>measurement? Anything above a certain threshold is a red flag...like
>my cholesterol level.

Right, but the point is where that threshold is set. Where I think it
should be set may not be the same place where you care to set it.

In some cases, the tests don't tell everything. For example, if you do
a typical test for a heavy metal, it cannot distinguish between soluble
salts which are very bad, and insoluble salts which are much less harmful.
So where you decide to put the threshold requires making some assumptions
about the composition in the first place.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."