Carbofuran: Toxicity, diagnosing poisoning and rehabilitation of poisoned birds - Carbofuran and Wildlife Poisoning: Global Perspectives and Forensic Approaches - page 19

2 Carbofuran: Toxicity,
diagnosing poisoning
and rehabilitation of
poisoned birds
Pierre Mineau, 1 Stuart Porter, 2 Carol Uphoff Meteyer 3
1 National Wildlife Research Centre, Science and Technology Branch, Environment
Canada, Ottawa, K1A 0H3, CANADA
2 Blue Ridge Community College, PO Box 80, 1 Community College Lane, Weyers
Cave, VA 24486, USA
3 National Wildlife Health Centre, US Geological Survey, 6006 Schroeder Rd.,
Madison, WI 53711, USA
2.1 Acute toxicity of carbofuran to birds and mammals
Of most relevance to the impacts of carbofuran documented in this topic is the acute toxicity of the
product. Like other carbamate insecticides carbofuran is a potent and direct cholinesterase inhibitor
that is toxic from the moment of exposure without the need for metabolic alteration.
It is sometimes diffi cult for non-toxicologists to appreciate the comparative toxicity of various
substances. We can start by listing LD 50 values in milligrams of active ingredient per kilogram of
bodyweight, a common measure in toxicology circles. This is the median lethal dose, or, the estimated
quantity of a substance required to kill half of a set of exposed individuals. However, when thinking
about the signifi cance of a given LD 50 value, a fair degree of mental gymnastics is required, especially
when the target organism (e.g., the birds) can vary in weight. Therefore, to provide a more graphic
illustration, we will where possible borrow from Rachel Carson's 'Aspirin™ index'. In recognising
that the average person may not relate very well to milligram/kilogram values, but that everyone
is familiar with a tablet of Aspirin ® ™, she calculated how many median lethal doses a tablet-sized
amount of pesticide would represent. The irony of using this well known Bayer product (Aspirin ® ™)
for this calculation (in view of Bayer's prominent role in the production and marketing of organophos-
phorous and carbamate insecticides) probably did not escape Ms. Carson. By dividing the number of