Environmental Engineering Reference
In-Depth Information
for carbofuran in corn and alfalfa. Overall, it appears that the LiquidPARAM
performed well for carbofuran, but may have over-predicted risk for fl owable
CPY, based on the results of fi eld studies conducted with CPY.
7
Risk Characterization for Granular Chlorpyrifos
For each exposure scenario, acute risk was determined using the same approach as
described in Sect.
6
for fl owable chlorpyrifos.
As with fl owable CPY, the dose-response curve used to estimate acute risk
depended on the focal species. If a dose-response curve was available for the focal
species of interest, that curve was used (i.e., northern bobwhite (
C. virginianus
),
red-winged blackbird (
A. phoeniceus
)). In the absence of species-specifi c dose-
response curves, acute dose-response curves were generated for three hypothetical
species representing a range of sensitivities. In this section, the results from the
GranPARAM modeling exercise are discussed. In addition, the results of avian fi eld
studies are discussed and compared to the results from the modeling exercise.
The section concludes with a discussion of sources of uncertainty and strengths of
the assessment for granular CPY.
7.1
Modeled Acute Risks from Granular CPY
Simulations conducted for granular CPY indicated that, with two exceptions, all
bird species were at
de minimis
risk, even if they had high sensitivity to granular
CPY (Table
8
). The two exceptions were for horned lark in corn/sweet corn and
tobacco, assuming that horned larks (
E. alpestris
) are highly sensitive to CPY.
Horned larks forage more in row crops than do any other focal species considered
in this assessment (SI Appendix 3, Sect. 1.2). In corn/sweet corn and tobacco,
survival of horned larks was predicted to be >95% (Table
8
).
7.2
Results of Field Studies for Granular CPY
Avian fi eld studies were performed with Lorsban 15G on corn fi elds in Iowa
(Frey et al.
1994
). Lorsban 15G was applied at 2.87 kg ha
−1
(2.6 lb ai A
−1
) at-planting
(ground banded), and at 1.07 kg ha
−1
(0.975 lb ai A
−1
) during the whorl and tassel
stages (aerial broadcast). Monitoring of fi eld sites for birds exhibiting signs of
toxicity was done prior to each application and for 13-d following each application,
including abundance determinations, carcass search effi ciency evaluations, and
residue analyses.
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