Refined Avian Risk Assessment for Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 200

Fig. 10 Percent mortality per application of Furadan ® 4F in corn and alfalfa as estimated by
LiquidPARAM, TIM (v1), and observed in fi eld studies by Booth et al. ( 1989 ) and Jorgensen
et al. ( 1989 )
birds per time step) as a point estimate. Free metabolic rate is treated as a distribution
in LiquidPARAM.
LiquidPARAM has several capabilities not available in TIM. These include:
(1) The ability to model exposure scenarios involving multiple applications of
pesticide taking place at a user-specifi ed interval; (2) Addition of many new crops;
(3) Addition of ten new focal bird species; and (4) The ability of users to select day
length, time of application for fi rst, second, and third applications, and length of
time that dew is present on treated fi elds.
As described in SI Appendix 3, Sect. 1.4, sensitivity analysis and evaluation of
model performance has been undertaken for LiquidPARAM. The sensitivity analysis
was useful in determining which variables had an important infl uence on acute and
chronic risk for bird species in high exposure scenarios (e.g., choice of drinking
water scenario and chronic averaging period in the chronic modeling simulations)
and in low exposure scenarios (varying any one factor had little effect on estimated
acute or chronic risk to birds regardless of assumed sensitivity).
In addition to the sensitivity analysis, the model for LiquidPARAM has been eval-
uated. Field studies involving the application of fl owable carbofuran, a carbamate
pesticide that inhibits brain and plasma acetylcholinesterase activity, and subsequent
determination of avian mortality were reviewed to determine those that could be used
to evaluate LiquidPARAM performance. Each of the selected studies (Booth et al.
1989 ; Jorgensen et al. 1989 ) reported mortality from applications of fl owable carbo-
furan. The exposure scenarios for the selected studies were run in LiquidPARAM to
determine how close model predictions were to fi eld observations. For the two fi eld
studies selected, LiquidPARAM predictions and fi eld observations of mortality were
similar, with LiquidPARAM slightly over-predicting risk. Conversely, EPA's TIM v1
vastly over-estimated risk of carbofuran compared to fi eld observations (Fig. 10 ).
Although LiquidPARAM model predictions and fi eld study results were fairly close