Ernie said:
>Hasn't it
> been shown that there is a trade off of dose required to produce
> an effect with time of exposure- such that an acute LD50 of 8 nanograms
> per bee, for instance, would convert to a chronic LD50 of perhaps
> less than 1, or even 0.1, nanogram per bee ?
>
Randy said:
No, hasn't been shown to the best of my knowledge.  The two papers that I
know of that imply that they do (Suchail and Tennekes) both have serious
flaws.


Randy,
The 2006 paper issued by the California Department ofPesticide Regulation
 by Matthew Fossen, Ph.D, enititled “Environmental Fate of Imidacloprid” , available at http://www.cdpr.ca.gov/docs/emon/pubs/fatememo/Imidclprdfate2.pdf
says,

< “Acute oral toxicity LD50 values for both Apis mellifera mellifera and Apis mellifera
 caucasica are approximately 5 ng/bee, while contact LD50 values are 14 ng/bee for
 A. m. caucasica and 24 ng/bee for A. m. mellifera (Suchail et al., 1999). Imidacloprid 
toxic in smaller doses when ingested over an extended period: chronic LD50 values 
range from 0.01–1.0 ng/bee (Suchail et al., 2001).>

Is Fossen’s reference to Suchail the paper* you are referring to ? Could you please 
describe the “serious flaws” that you have found? Perhaps this topic header should
now become something else- like "Acute LD50 versus Chronic LD50" ? It seem like
this is an important subject and ought to be the basis of future sound science 
investigations and of future regulatory actions.
Thank you,
                 Ernie

*Suchail, S., D. Guez, and L.P. Belzunces. 1999. Characteristics of imidacloprid toxicity in
 two Apis mellifera subspecies. Environ. Toxicol. Chem. 19(7): 1901–1905.

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