The U.S. Environmental Protection Agency (EPA) regulates
all pesticides and pest control agents to ensure that their use
causes no unreasonable adverse effects on the environment or non-target
organisms. This includes crop varieties genetically modified to
express proteins that protect the plant from insects or other pests.
Such registration is granted by EPA only after the agency
has data to answer specific questions about safety.
Bt corn is enhanced through biotechnology to protect against
insect pests. Its built-in insect protection comes from a naturally
occurring microorganism called Bacillus thuringiensis or
Bt. The protein produced by Bt corn selectively
targets caterpillars within the order of Lepidoptera. This order
includes several moth species harmful to corn, as well as other
non-target butterfly species such as the monarch. The primary target
is the European corn borer, a moth caterpillar that feeds on cornstalks
and ears. Yield losses and the cost of controlling the European
corn borer are staggering, estimated at more than $1 billion annually.
Prior to the registration of Bt corn, EPA examined risk assessment
data to evaluate the potential effects on a wide range of organisms,
including birds, aquatic invertebrates, honey bees, ladybird beetles,
earthworms and other non-target organisms.
EPA concluded that the Agency can foresee no unreasonable
adverse effects to non-target organisms, including butterflies
(U.S. EPA, 1995).
This EPA conclusion that non-target butterflies would not
be adversely impacted was based on knowledge that butterfly
or caterpillar exposure to Bt corn in the environment would
be low. Exposure would be limited to caterpillars developing on
weeds within cornfields or very near to cornfields during pollen
shed. The fact that pollen moves only a short distance away from
cornfields also would limit exposure, as well as the low concentration
of milkweeds typically found in cornfields.
Although the EPA tested Bt
corn or pollen on representative organisms rather
than all non-target organisms, we believe the EPA based its
decision to register this product on sound science and well-reasoned