Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 255

Data on non- Apis bees was scant, and data available for NTA as surrogates for
non- Apis pollinators was not usable in the risk assessment. However, in many cases
the honey bee is a suitable surrogate for exposure and effects in other pollinating
insects. Since all insect pollinators have in common certain aspects of their behav-
ior, biology, and ecology, worst-case exposures for honey bees should generally be
protective of non- Apis bees. However, there are a number of biological and ecologi-
cal characteristics of these taxa that can influence risk. Some of these have been
described previously and relate to: the role of the queen in founding nests in the
spring; increased susceptibility due to smaller colony nest size (i.e., less redun-
dancy); the smaller size of some of non- Apis bees that leads to greater potential for
exposure (i.e., greater surface area:volume ratio); the smaller foraging range; and
the location and construction of nests (EFSA 2012 ; Thompson and Hunt 1999 ).
We identified several data gaps and areas of uncertainty in our assessment of
CPY on pollinators. Below, we summarize key research topics that deserve more
research attention, many of which are relevant to other insecticides:

• Given the increasing recognition of the significant role that wild bees have in

agricultural and natural ecosystems (Garibaldi et al. 2013 ), more data are needed
on non- Apis species to accurately evaluate the risk of CPY to these taxa as part
of higher tier testing.

• More information on sublethal effects of CPY on pollinators is needed, in view

of the recent increased focus on behavioral effects such as navigation to and from
the hive. However, accepted guidelines for sublethal tests are also required.

• The stability and rate of degradation of CPY residues in nectar, pollen, and bees

wax should be determined. Area-wide concentrations have been reported in
monitoring studies, but the concentrations of CPY in nectar and pollen over time,
following a defined field application, have not been quantified. Concentrations
are expected to be lower on pollen and nectar than foliage for non-systemic
insecticides like CPY, but the Tier-1 assessment models assume the same levels
are present in all parts of the plant. In addition, depending on floral phenology,
pollen present at the time of application will likely be available or attractive to
foraging pollinators for only a few days after application. Quantification of con-
centrations of CPY in pollen and nectar over time after application would help to
refine the risk assessment and facilitate testing in the laboratory with environ-
mentally relevant concentrations and routes of exposure.

• How CPY partitions and transfers between wax and bee brood or the food stored

in wax cells is unknown. It is possible that wax represents a sink for CPY in the
colony and that the residues are not bio-available when present at the concentra-
tions that have been reported in wax. Although there can be a risk of sublethal
effects from residue in wax for some pesticides, this was not the case for CPY
(Wu et al. 2011 ).

• Partitioning of CPY from wax, in the range of concentrations that have been

reported, into the airspace of a colony should be quantified. The physical proper-
ties of CPY and its strong propensity to partition into nonpolar substances makes