Hello all,
I am thinking about the following two principles of toxicology, and how they relate to beekeeping:
1. Haber's rule states that Dt = c, where D is dose, t is time, and c is a constant. This rule was developed and tested by a German chemist trying to figure out how long a poisonous gas of a given concentration must be breathed to produce death, or other toxic effect (Witschi, 1999). The consequence of this simple relationship is that smaller doses over longer times will have the same effect as larger doses over shorter times.
Witschi, Hanspeter 1999. Some notes on the history of Haber's Law. Toxicological Sciences vol. 50, 164-168
2. There are three independent time scales that can affect Haber's rule: Dynamic (intrinsic property of the compound), Kinetic (intrinsic property of the organism), and Frequency of Exposure. One result is that, if the compound has a long half-life (dynamic), then a smaller dose over a longer time can actually have a greater effect than predicted by Haber's Law, because the effect is cumulative (rate of removal of the compound < rate of addition). The same thing happens if the kinetic effect is large (the organism cannot metabolize the compound effectively, for example).
Rozman, Karl K. (2000) Approaches for Using Toxicokinetic Information in Assessing Risk to Deployed U.S. Forces. IN: Strategies to Protect the Health of Deployed U.S. Forces: Assessing Health Risks to Deployed U.S. Forces -- Workshop Proceedings Board on Environmental Studies and Toxicology, National Research Council
One conclusion I come to, where beekeeping is concerned, is that this is why we are told to remove foundations more than three years old.
Many (most?) of the studies discussed on the Bee-L listserve have been whole-colony studies. How are crop pesticides officially evaluated with respect to bee toxicity? I've been told that insect toxicity in the US is determined based on the LD50 of adult insects held in incubators that are given measured, acute doses (thus, "tightly controlled" for dosage). LD50 is evaluated some 3 days later or so....longer term mortality is not assessed.
While many honeybee colony stressors have been acknowledged, beekeepers focus on Varroa because it causes the most acute problems. The predominant attitude I'm reading here seems to be a pragmatic one...split and treat, break the brood cycle, split and treat.....this will dilute the various stressors enough to keep the bees alive. Won't this approach ultimately fail?
Sincerely,
Christina (upstate NY)
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