I said:

>> I'm sorry, but 192 ppb is the consensus number...
>>
>> LD50 values range from 0.0037 to greater than 
>> 0.070 µg/bee...

Juanse Barros asked:
	
> Please James , can you iluminate me?
> How do you transform from µg/bee to ppb?
	
I love it when someone says to themselves
"Wait a minute, let's do the math..."


LD50 is expressed in "micrograms per bee". 
To get to parts-per-billion you take the
LD50 value and:

1) Divide by the amount of sucrose solution 
   ingested by a bee in an LD50 test (in mg)

2) Multiply by 1 million to convert the answer from 
   parts per thousand to parts per billion 

Some people call the "parts per billion" number
the "LC50" - the lethal concentration that kills 
half the bees in the specified time period.

So, if the bees were fed 26 mg in total syrup, 
and the LD50 is found to be 0.005 µg/bee:

LC50 = (LD50 / 26) * 1,000,000 

LC50 = (0.005 / 26) * 1,000,000 

LC50 = (1.9230 * (1 * 10^-4)) * (1 * 10^6)

LC50 = 1.9230 * 10^2

LC50 = 192.30 ppb

LC50 ~ 192 ppb

Another point that misleads people is the entire concept
of a "chronic feeding test" versus an "acute feeding test".

Both tests are done, and if the results are about the same,
one can prove that the material is metabolized by the
bees, which is a good thing.   When the "chronic", feeding
kills bees at lower doses that the "acute" feeding, then
the material bio-accumulates.  But these pesticides are
designed, not discovered, so everyone knows going into
the game if bees can metabolize the stuff or not.

The testing of the "10-day chronic" response is done
to verify the point to beekeepers, the EPA, and the
public.  Yes, there will be a "chronic" number, but
when it is about the same as the "acute" number, there
is no bio-accumulation.

One of the big accusations made is that imidacloprid has
"sublethal effects" at low levels, but for this to be
true, it would mean that the whole issue of "do bees
metabolize imidacloprid" would have to be unresolved.
People who make this accusation are self-identifying
as either unable to read scientific papers, or conspiracy
theorists who think that the data was faked.

It may sound difficult to impossible to us beekeepers,
but the toxicology guys know this stuff cold, and
can say such things with a full knowledge of the 
chemistry of the pesticide and the bee's digestive
system.

There is also the "No-Adverse-Effect Concentration",
which is another parts-per-billion number, and is
the highest level tested where no change was observed
in bee behavior.  This is the sort of level that is
being measured by the Dively/Embry/Pettis study, as
they are looking for subtle changes in gestalt colony
operations, rather than just deaths. 

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