TIM v3.0

(Terrestrial Investigation Model)

Presentation to the EMPM

TIM team: Brian Anderson, Kris Garber, Nick Mastrota, Ed Odenkirchen

10/28/14

1
Outline

• Model overview

• Discussion of model components

• Bird behavior

• Different exposure routes

• Mortality

• Model results

• Example application

• Future work

2
Model Overview

Drinking

D

e

r

m

al

Adjacent area Treated field

(receives spray drift)

3
Model Overview

Drinking

D

erm

al

Adjacent area Treated field

(receives spray drift)

4
Model overview

• Each exposure route considers

• Uptake rate

• Environmental concentration

• Total dose at any time step 

• Sum of all exposure routes at that time step

• Carryover from previous time step

• Elimination

• Converted to oral-equivalent

• Mortality occurs when total dose exceeds individual sensitivity

• Selected from dose-response curve based on LD50 and slope

inhalation t dermal t total t retained t

Dtotal t Ddiet t Ddrinking D D D ( 1)* F ( ) ( ) ( )

( ) 

( )

    

5
Variability and Uncertainty

• The model uses distributions to account for many sources of 

variability

• Body weight

• Consumption rates

• Environmental concentrations

• Bird movement

• Uncertainty associated with model parameters can be addressed by 

the model user

• For example: entering ranges of LD50 and confidence intervals of slope values 

to bound risk predictions

6
Species parameters

• Body Weight

• Diet

• Frequency on field and fidelity factor

• 30 generic species

• 3 body sizes (small, medium, large)

• 5 diets (insectivore, granivore, herbivore, frugivore, omnivore)

• 2 resident statuses (field, edge)

• Custom species

• Non-listed and listed

7
Bird behavior

• Feeding times

• Bimodal feeding pattern 

(morning and afternoon)

• Movement

• Birds move between each time step during 

feeding period

• Birds are on the nest when not feeding

• Several exposure routes are 0 when not 

feeding

• Diet, drinking, dermal

• Field and edge residents treated differently

Hypothetical examples of the avian bimodal 

feeding pattern. X-axis is hour of day; Y-axis is 

daily dietary fraction.

8
Spray drift transport (new to version 3)

• Model includes spray drift deposition calculations

• Considers movement of bird on and off field

• Calculates distance from edge of field based on size of home range

• Nest located at center of home range

Area with 

no pesticide 

exposure 

Treated field Spray 

drift 

zone

Bird #1 

Home 

range

d1

d2

d

d’

Bird #2 

Home 

range

304 m

d3’

9
Exposures

• Function of uptake and concentration

• Uptake rates based on allometric equations

• Concentrations in air and water based on equilibrium partitioning models

• Food items considered

• Arthropods, seeds, fruit, grass, broadleaf

• Inhalation

• Droplets and volatilized residues

• Dermal

• Direct spray and contact with foliage

• Drinking water

• Puddle and dew

10
Comparison of 

different versions

• FIFRA SAP Reviews

• Version 1: 2001

• Version 2: 2004

Model Component version 1.0

(2-21-2001)

version 2.0

(3-10-2004)

version 3.0

(9-2014)

Species considered Focal Generic Generic or focal

Duration of exposure 7 days User defined User defined

Time step User defined Hourly Hourly

Exposure routes 

considered

Dietary

Drinking water

Dietary

Drinking water 

Inhalation

Dermal

Dietary 

Drinking water

Inhalation

Dermal

Spray drift No No Yes

Feeding pattern Unimodal Bimodal Bimodal

Serial correlation 

between foraging events

None Yes Yes

Drinking water exposure 

from puddles

Addressed using 

PRZM4 outputs

Addressed using 

complex model 

comparable to 

PRZM4 conceptual 

model

Addressed using 

equilibrium partitioning 

approach

Number of pesticide 

applications modeled

1 1 Up to 5

User has ability to turn 

on/off exposure routes

Yes No Yes

Model platform Excel and 

Crystal Ball

C executable 

with Excel GUI

C executable (currently 

working on developing 

Matlab GUI)

11
Model results

• Number of dead birds

• Probabilities associated with killing x birds out of a flock

• PDF (probability associated with killing exactly x birds)

• CDF (probability of killing ≤ x birds)

• CCDF (probability of killing > x birds)

• Relative importance of exposure routes

• Time of death

12
Example application

13
Species of interest: Lesser Prairie Chicken

• Threatened species

• Population estimate = 37,000 birds 

• Location: CO, KS, NM, OK, TX

• Characteristics of adults

• BW: 727 g (mean for females)

• Diet: insects, seeds, grass

• Edge nester

• Available information indicates that individuals may visit agricultural fields in 

Spring and Fall to consume seeds

• Insects, grass and seeds are expected to be consumed throughout the year in 

their native habitat, which is prairie

14
Pesticide of interest • Very highly toxic to birds • LD50 for bobwhite quail = 5.2 mg/kg

-bw

• Fate properties • Mobile (Koc = 600) • Moderately persistent • Foliar dissipation half-life = 5 d • Aerobic soil metabolism half life = 40 

d

• Semi volatile

• Use• Corn • 1 ground application at 2 lb a.i./A

15
Tier I results

• T-REX acute dose-based RQs (BW = 727 g) exceed listed species LOC (0.1) 

for all food items

• AgDRIFT analysis indicates that risk extends as far as 470 feet from edge 

of field (EOF)

• Conclusion: potential risk of mortality to individuals consuming seeds on 

treated field and other food items within edge habitat

Food item upper bound RQ mean RQ

Distance (ft) from EOF 

where risks extend

Short Grass 24 8.6 470

Tall Grass 11 3.6 260

Arthropods 9.5 6.6 220

Seeds 0.34 0.16 10

16
Tier II analysis with TIM

• Two scenarios:

• Individuals nest in edge habitat that receives spray drift

• Adults do not forage on treated field

• Adults are assumed to be within 1000 feet from EOF

• Diet: insects (55%), seeds (22%), grass (23%)

• Individuals forage in field for seeds after corn is harvested

• Dermal and inhalation routes turned off

17
Results

• Scenario 1 (spray drift)

• Mortality to 0.62% of simulated birds 

• Very fine to fine droplet spectrum

• Probability of mortality to one or more birds (out of 25): 0.14

• Diet was dominant route of exposure for dead birds

• No mortality to any simulated birds with fine to medium/coarse droplets

• Scenario 2 (consumption of seeds and puddles on field)

• Mortality to 0.50% of simulated birds

• Probability of mortality to one or more birds: 0.12

• 50% rate reduction results in substantially lower risk of mortality 

• Probability of mortality to one or more birds: 0.0094

18
Conclusions

• The current use pattern poses a risk to individual lesser prairie 

chickens

• Potential mitigation options for reducing risks include:

• Use of spray nozzles that produce medium/coarse droplets

• Rate reductions

19
Future work

• Beta test

• Sensitivity analysis

• Explore application of TIM for ESA case studies

• Diazinon, chlorpyrifos, malathion

• Integrate TIM and MCnest

• Develop GUI

• Add population model

20