Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 233

study on cotton, the concentration of CPY declined to 3.6% of its initial value at
24 h and probably would not be efficacious for pest control (Buck et al. 1980 ). This
suggests that exposure to pollinators would also be below toxic doses within a day
after application. From reported values in Table 4 , geometric means for concentra-
tions of dislodgeable CPY at 0 and 3-4 d after spraying were 1.46 and 0.019 μg cm −2 ,
respectively (adjusted for a 1.12 kg ha −1 application rate).
Reported effects of irrigation on the concentration of dislodgeable residues on
foliar surfaces have been variable (Table 4 ). Whereas immediate post-application
irrigation did not affect the concentration of dislodgeable CPY from leaves of turf
grass (Hurto and Prinster 1993 ), significant reductions in concentrations of CPY on
grass foliage were found (4-fold difference after 6 h) following post-spray irrigating
with water, as recommended by the product label instructions for most turf insect
control situations (Goh et al. 1986 ).
At least two studies have also examined dislodgeable concentrations of CPYO.
After applications at 11.2 kg CPY ha −1 , no CYPO was detected with a detection
limit of 0.01 μg cm −2 . The results also showed very rapid disappearance of the par-
ent insecticide (Iwata et al. 1983 ). On grapefruit leaves, trace amounts (0.013-
0.028 μg cm −2 ) of CPYO were detected in samples collected 3 d after application.
When applied to cranberry at 2 kg ha −1 , small amounts of CPYO were initially
detected (<7 μg kg −1 ), but did not accumulate (Putnam et al. 2003 ). These results
indicate that any CYPO formed on foliage is rapidly dissipated and does not accu-
mulate. Given the demonstrated lack of potential exposure, higher Tier-refinement
of the potential exposure to CPYO is not required.

3.5 Other Potential Routes of Exposure

Exposure via beeswax . Although wax is not consumed as food, there is direct
contact between wax cell surfaces and food or individuals. Residues initially present
in the wax could come from sublethal concentrations of CPY inside the body of
bees that secrete the wax. After it is secreted, it may accumulate from contact with
bees, pollen, nectar or other materials. The transfer of residues into or from wax is
reversible and given the nonpolar nature of CPY it is likely that the partition of CPY
between wax and bees or food substances tends toward equilibrium with higher
concentrations in the wax. The net effect of absorption into wax is to reduce the
potential for exposure of bees to CPY.
Several of the North American and European studies mentioned above examined
concentrations of pesticides in beeswax collected from honey bee hives. Mullin
et al. ( 2010 ) found CPY more often in foundation wax than in comb, but at similar
concentrations (Table 5 ). Excluding pesticides that are used by beekeepers within
hives to control Varroa mite parasites (fluvalinate, coumaphos, and its degradate
coumaphos oxon), CPY was the most frequently detected pesticide in beeswax of
the 118 pesticides and metabolites analyzed (Mullin et al. 2010 ). CPY was detected
less often in beeswax collected from hives in France (Chauzat et al. 2011 ) and Spain