Refined Avian Risk Assessment for Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 198

Fig. 8 Percentage of bird
species affected versus
percent mortality for fl owable
chlorpyrifos applied
broadcast at-plant and band
post-plant at a rate of
1.12 kg ha −1 (1 lb ai A −1 ) 3×
with a 10-d interval to corn
fi elds

6.4 Discussion of Avian Risks for Flowable CPY

There are a number of bird species that frequent agroecosystems besides those
included as focal species in this assessment (see Best and Murray 2003 ). The
USEPA (USEPA 2005 ) used estimates of mortality for the combination of focal
species and bird sensitivities in each modeled exposure scenario to approximate the
cumulative distribution of outcomes for the complex of species using treated fi elds.
The approach assumes that the focal species included in the modeling exercise are
representative of the birds and their exposures occurring in the fi elds (USEPA
2005 ). This assumption is supported by the selection of focal species known to
occur on the treated crops by actual survey (e.g., Best and Murray 2003 ). According
to the USEPA ( 2005 ), the outcomes of the three modeled sensitivity assumptions
(low, median and high sensitivity) “can be viewed as a stratifi ed sample from the
population which estimates the limits and mid points of the cumulative risk distribution
and therefore provides a reasonable approximation of the distribution.”
The resulting cumulative distribution of acute risk for banded application on
corn at the maximum application rate of 1.12 kg ha −1 (1 lb ai A −1 ) is shown in Fig. 8 .
Results of simulations using LiquidPARAM indicate that several species of birds, if
highly sensitive, would experience up to approximately 30% mortality. Similar
results were predicted for alfalfa, almond, apple/cherry, grape, grapefruit and
soybean (Table 5 ). For orange, somewhat greater risk is expected in the bird com-
munity because this crop has the greatest application rate allowed on the Lorsban
Advanced label (i.e., 6.27 kg ha −1 (5.6 lb ai A −1 )) (Fig. 9 ).
Although the results of the LiquidPARAM modeling indicated some acute risk
to the most sensitive species for several crops listed on the Lorsban Advanced label
(Table 5 ), the evidence from fi eld studies that used the corresponding application
rates (i.e., corn, grapefruit, and orange) indicate that fl owable CPY poses little risk
to birds (Dittrich and Staedtler 2010 ; Frey et al. 1994 ; Gallagher et al. 1994 ; Selbach
and Wilkens 2008b ; Wolf et al. 2010 ). Thus, it would appear that LiquidPARAM