Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 248

Incident report data were also obtained from the Pest Management Regulatory
Agency (PMRA) of Health Canada. Since 2007, when reporting of honey bee pes-
ticide incidents was officially initiated, there have been only nine reports potentially
implicating CPY as the cause of the incident. All reports were from the province of
Saskatchewan in 2012. Four of these incidents were classified as “minor” by PMRA
(≤10% of bees suffering lethal or sublethal effects), three were classified as “mod-
erate” (10-30% of bee affected), and two incidents were classified as “major”
(≤30% affected).

5 Characterization of Risk of CPY to Pollinators

Hazards and risks were calculated using the margin of exposure method to generate
RQ values. For CPY, the hazard to honey bees and other pollinators from direct
exposure during spray is well known. This has been dealt with through mitigation
measures to protect pollinators through restricted use patterns that minimize direct
exposure to spray or spray drift during application (see discussion of Tier-1 expo-
sure above). The following paragraphs cover the calculation of RQ values and
assessment of the potential risk to pollinators from post-application exposure.

5.1 Estimates of Risk to Honey Bees

Estimated risk to honey bees through dietary exposure . The geometric mean of LD 50
values from dietary tests using technical CPY was less than that derived from tests
with formulated product (Table 7 ). The geometric mean of the oral LD 50 for technical
CPY (0.114 μg CPY bee −1 ) was used as a worst case in calculating RQs.
The upper limit dietary intake of CPY per day can be estimated for different life
stages of honey bees based on surrogate T-REX screening values for pollen and
nectar (USEPA 2012 ), or empirical data collected from pollen and honey and/or
nectar in the field. The proposed Tier-1 scheme includes an acute oral LOC of 0.4
for adult and larval honey bees that is compared to estimates of RQs for exposure
and effects. Using the maximum screening values suggested in the USEPA's pro-
posed risk assessment scheme for pollinators (Table 1 ), RQ values for oral exposure
of adult and larval honey bees following sprays of CPY exceeded the LOC by over
three orders of magnitude.
Tier-1 estimates of oral exposures based on T-REX are intended to be conserva-
tive, when compared to data for concentrations of CPY collected in the field. Tier-2
estimates are based on measured values of CPY in honey bee food and reflect actual
use conditions. Using the monitoring data for concentrations in pollen collected
from commercial beehives in the U.S. by Mullin et al. ( 2010 ) and food consumption
rates established by the USEPA (USEPA 2012 ), the upper 95th centile dietary expo-
sures were 0.066 μg CPY d −1 for adult bees and 0.027 μg CPY d −1 for larvae