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The monarch risk assessment has two basic components:
What is the potential for toxicity for a particular species?
What is the likelihood of exposure to the toxicant?
This is the standardized approach for estimating risk posed by pesticides, industrial byproducts and other potential toxicants to many non-target species. The scientific community considers it the most credible method for determining actual risk and it is also the method accepted by the EPA.
Examination of the natural habitat of monarch butterflies indicates several events must coincide for the possibility to even exist that Bt pollen could cause harm to the monarch population. First, monarchs have to have laid eggs on milkweed plants and the caterpillars must emerge from the eggs just as the Bt corn is producing pollen. Corn, including genetically modified corn, only produces pollen during a narrow window of seven to 10 days each year. Next, the caterpillars must feed on milkweed leaves with Bt corn pollen. Third, the caterpillars must consume enough Bt pollen to reach potentially toxic levels. The Bt corn/monarch risk assessment assembled the likelihood of all of these circumstances occurring.
The risk assessment’s key finding: The potential risk to monarch butterfly populations from Bt corn pollen is negligible.
Examination of the natural habitat of monarch butterflies indicates several events must coincide for the possibility to even exist that Bt pollen could cause harm to the monarch population.