Ecological Risk Assessment of the Uses of the Organophosphorus Insecticide Chlorpyrifos, in the United States - Reviews of Environmental Contamination and Toxicology - page 8

been a number of amendments to the label. These included reductions in single and
seasonal application rates, reductions in number of applications per season, and
increases in minimum re-treatment intervals (USEPA 2009 ). These changes and
their effects on risk to birds were addressed in this paper (Moore et al. 2014 ).
Refi ned risk assessments for birds exposed to CPY were conducted for a range
of current use patterns for each formulation in the U.S. The assessments relied on
focal bird species that commonly occur in and around areas where CPY might be
applied and for which adequate data were available to quantify their foraging behav-
ior and diets.
A refi ned version of Liquid Pesticide Avian Risk Assessment Model
(LiquidPARAM) was developed for the assessment of the risks of repeated uses of
fl owable formulations of CPY. Flowable formulations of CPY are registered for a
variety of fi eld and tree crops in the U.S. Focal species of birds associated with these
crops were selected for inclusion in the model. The major routes of exposure for
birds to fl owable CPY were consumption of treated dietary items and drinking
water. For acute exposure, LiquidPARAM was used to estimate the maximum
retained dose in each of 20 birds on each of 1,000 treated fi elds over the 60-d period
following initial application to account for multiple applications. For each bird, the
standard normal Z score for the maximum retained dose was determined from the
appropriate probit dose-response curve and was then compared to a randomly
drawn value from a uniform distribution with a range of 0 to 1 to determine whether
the bird survived or died. For species lacking acceptable acute oral toxicity data (all
focal species except northern bobwhite and red-winged blackbird), a SSD approach
was used to generate hypothetical dose-response curves assuming high, median and
low sensitivity to CPY. For acute risk, risk curves were generated for each use pat-
tern and exposure scenario. The risk curves show the relationship between exceed-
ance probability and percent mortality.
The results of the LiquidPARAM modeling indicated that fl owable CPY poses
an acute risk to some bird species, particularly those species that are highly sensitive
and forage extensively in crops with large maximum application rates (e.g., grape-
fruit and orange; 6.3 kg a.i. ha −1 ). Overall, most species of birds would not experi-
ence signifi cant mortality as a result of exposure to fl owable CPY. The results of a
number of fi eld studies conducted in the U.S. and EU at application rates similar to
those on the Lorsban ® Advanced label indicated that fl owable CPY rarely causes
avian mortality and suggest that LiquidPARAM is likely over-estimating acute risk
to birds for fl owable CPY. A lack of well-documented bird-kill incidents associated
with normal use since 2002 support the conclusions of the fi eld studies. Of the two
bird-kill incidents reported between 2002 and 2009, one was from a misuse and the
other lacked suffi cient information to make a determination of causality.
For estimating chronic exposure risks, the maximum average total daily intake
was compared to the chronic no-observed-effect-level (NOEL) and lowest-observed-
effect-level (LOEL) from the Mallard. The probabilities of exceeding the LOEL
were very small, thus indicating that CPY is not a chronic risk concern for birds.
Risks resulting from the use of granular CPY were estimated using the Granular
Pesticide Avian Risk Model (GranPARAM) model. Granular CPY is registered for