Environmental Engineering Reference
In-Depth Information
surface water from wet soil and ephemeral pools, which are accessible to bees and
can be contaminated with pesticides through rain, runoff, or from soil surfaces. CPY
on vegetation and in air can contribute to residues in rainwater and dew on plant
surfaces that can be directly toxic, or can be returned to the hive/nest by foragers
collecting water as part of the sublethal body burden (Gary 1975 ). If CPY is present
in air, it can appear briefly in rainwater before hydrolysis occurs (Tunink 2010 ) or
the water dries. The release of residues from surfaces of leaves following rain after
a spray has dried should be limited due to the high affinity of CPY for nonpolar
media (Solomon et al. 2014 ). No information on collection of water by non- Apis
pollinators or where they obtain it was found, but scenarios for exposure of honey
bees from water should be protective of non- Apis taxa, because they provide water
for the hive and carry larger amounts.
Foliage and flower parts other than pollen represent a potential source of contact
exposure for foraging pollinators. Leaf cutting bees (Megachilidae) may be particu-
larly affected by dried residues of CPY on foliage since they cut and collect leaf
discs for construction of their nest cells. Plant resin, e.g. from poplar buds, was
included in the foliage compartment since honey bees collect small amounts of this
material in making propolis. These materials could contain residues from off target
drift, but propolis was considered to represent an insignificant exposure route to
honey bee foragers (Fig. 1 ).
Soil and soil-water represent a potential pathway of exposure to CPY for pollina-
tors that are ground nesters, or use soil in building nest cells, such as mason bees.
These exposures can be from sprayable formulations or granular CPY that dissolves
into soil-water.
Secondary routes of exposure . With social pollinating insects, such as honey bees
and bumble bees, secondary exposure to pesticides can occur in other adults or
offspring if the pesticide is brought back to the hive or nest and deposited in food
or other materials, or transferred to other individuals (Fig. 1 ). Solitary bees such as
alfalfa leafcutting bees or mason bees would not transfer residues to other adults,
but larvae could be exposed orally to residues in food provisions; both larvae and
eggs could potentially be exposed by contact with nesting materials that were con-
taminated in the field. Residues can also be excreted by honey bees in wax, which
is produced metabolically and secreted by bees for construction of honeycomb.
Residues in wax could originate from the sublethal body burden of CPY in bees as
they produce the wax, by partitioning of CPY from contaminated pollen or nectar,
and possibly by partitioning of CPY vapor from the air in the hive. As noted, CPY
is not persistent in air and the maximum concentration of CPY in air is expected
to be less than 250 ng m −3 . Thus transfer of CPY from air into wax in the hive is
likely an insignificant pathway (Fig. 1 ). The potential for exposure via transfer of
CPY from wax is low because wax is not consumed as food and because CPY is
strongly lipophilic, with a Log K OW of 5.0 (Mackay et al. 2014 ). This predicts that
partitioning from wax into eggs, larvae, royal jelly, honey, or stored pollen is unfa-
vorable. Wax is more likely a sink for CPY residues in the hive than a potential
pathway for exposure.
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