Environmental Engineering Reference
In-Depth Information
it unlikely that volatility from wax in a honey bee hive is a significant exposure
pathway. Partitioning of vapor from air into wax is more likely.
•
The transfer of CPY from soil or foliage during nest construction is expected to
be minor or insignificant, except in the first few hours after application. However,
tests on the transfer of CPY from nesting materials on a variety of species is
needed to confirm that this route of exposure is negligible, and it may be that the
exposure is so low that differences in species sensitivity are unimportant. As this
route of exposure is one of the key differences between the exposure pathways
encountered by foraging honey bees and many solitary pollinators, new research
results would clarify the usefulness of honey bees as a surrogate for other
species.
•
The significance of extra-floral nectaries as a food source and potential route of
exposure appears to be minor, but has not been quantified.
6
Summary
CPY is an organophosphorus insecticide that is widely used in North American
agriculture. It is non-systemic, comes in several sprayable and granular formula-
tions, and is used on a number of high-acreage crops on which pollinators can for-
age, including tree fruits, alfalfa, corn, sunflower, and almonds. Bees (Apoidea) are
the most important pollinators of agricultural crops in North America and were the
main pollinators of interest in this risk assessment.
The conceptual model identified a number of potential exposure pathways for
pollinators, some more significant than others. CPY is classified as being highly
toxic to honey bees by direct contact exposure. However, label precautions and
good agricultural practices prohibit application of CPY when bees are flying and/or
when flowering crops or weeds are present in the treatment area. Therefore, the risk
of CPY to pollinators through direct contact exposure should be small. The main
hazards for primary exposure for honey bees are dietary and contact exposure from
flowers that were sprayed during application and remain available to bees after
application. The main pathways for potential secondary exposure to CPY is through
pollen and nectar brought to the hive by forager bees and the sublethal body burden
of CPY carried on forager bees. Foraging for other materials, including water or
propolis, does not appear to be an important exposure route. Since adult forager
honey bees are most exposed, their protection from exposure via pollen, honey, and
contact with plant surfaces is expected to be protective of other life stages and castes
of honey bees.
Tier-1 approaches to estimate oral exposure to CPY through pollen and nectar/
honey, the principle food sources for honey bees, suggested that CPY poses a risk to
honey bees through consumption of pollen and nectar. However, a Tier-2 assess-
ment of concentrations reported in pollen and honey from monitoring work in North
America indicated there is little risk of acute toxicity from CPY through consump-
tion of these food sources.
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