Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 246

Table 10 Concentrations of chlorpyrifos (CPY) detected in honey bees
Concentration ( μ g kg −1 )

95th
centile b Mean a Median b Maximum b LOD c % of samples Reference

3.4 2.2 10.7 9.7 0.1 8.6 (12/140) Mullin et al. ( 2010 )

ND d - ND - 10.0 0 (0/307) Chauzat et al. ( 2011 )

43 - 57 - 30.0 e 3.2 (3/92) Ghini et al. ( 2004 )

77 - 80.6 NA NA NA DeGrandi-Hoffman

et al. ( 2013 )

a Based on positive detections
b Based on calculations that included 0 μg kg −1 for non-detections
c Limit of detection
d ND = CPY was included in residue analysis but was not detected
e Limit of quantification

with 955 μg CPY kg −1 was compared to that in colonies with free access to flora of
the southwestern US desert (DeGrandi-Hoffman et al. 2013 ). The experiment was
repeated using the same pollen to which Pristine ® (boscalid + pyraclostrobin) fungi-
cide was added. The authors reported that deformed wing virus (DWV) was not
detected in emerged queens grafted from or reared in the reference colonies but was
found in all emerged queens grafted from or reared in colonies where pollen con-
tained CPY (DeGrandi-Hoffman et al. 2013 ). Titres of DWV in queen larvae and
emerged queens were less than two-fold those in nurse bees in some treatments.
This study had a number of weaknesses. Treatments were not matched to appro-
priate controls. Bees exposed to CPY were restricted to almond pollen alone with
no reserves of other pollen in the hive. Pollen from almond trees might not have
been nutritionally sufficient (Somerville 2005 ) and contains the natural toxin amyg-
dalin at concentrations that are sublethal for honey bees (Somerville 2005 ). In con-
trast, control bees were free to forage on plants of the southwestern desert, which
are known to provide the complete nutritional requirement for bees (Ayers and
Harman 1992 ); the correct control should have been almond pollen without CPY.
Thus, potential nutritional effects from different pollen sources were confounded
with the potential effects of CPY and the applied fungicides. It was not clear whether
the uncaged, reference colonies had reserves of pollen or bee bread. Also, there was
no evidence of exposure of the queens. CPY was not detected in royal jelly or in
queens so exposures, if any, were less the limit of detection (0.1 μg kg −1 wwt) and
much less than a toxic dose (Table 7 ). CPY was detected in nurse bees but no symp-
toms of toxicity were described and they had lower titres of virus, which is the
opposite of what would be expected if there were a relationship between CPY expo-
sure and titer of virus. Another weakness of the study was exposure to only one
concentration of CPY, which precluded the characterization of a concentration-
response, a key factor in the determination of causality.

Concentrations of CPY found in honey bees . Pollinators can be exposed to CPY by
contact with spray droplets or residues on surfaces such as pollen, foliage or blos-
soms. The extent of transfer of these residues to pollinators can be estimated from
published residue data for CPY in bees (Table 10 ). CPY was detected in a small