EMPM

OTHER EXPOSURE PATHWAYS: 

DRINKING WATER 

INHALATION 

AND DERMAL

Ed Odenkirchen

Environmental Fate and Effects Division

Office of Pesticide Programs

January 10, 2011

1
SPECIAL THANKS TO....

 Tiffany Mason (SIP)

 Joseph Decant (STIR)

 Gabe Rothman (Inhalation Risk Tier 1)

 Charles Peck (Inhalation Risk Tier 1) 

 Tanja Crk (DUST)

2
STATEMENT OF THE ISSUES

 Current wildlife exposure methods do not typically 

consider dermal, inhalation and drinking water 

exposures

 Problem formulations, conceptual models, and 

decisions to advance to higher tier risk 

assessments should justify the inclusion or 

exclusion of any exposure routes considered

 Office of Research and Development methods do 

not routinely recommend dermal and inhalation 

routes for Superfund-type assessments, but do 

recommend a case-by-case consideration for 

situations like pesticide use risk assessments

3
STATEMENT OF THE ISSUES (CONT.)

 Approaches for decisions regarding inclusion of 

exposure routes in risk assessment should be 

transparent and consistent

 Challenge is to avoid revamping entire process 

while accounting for other route contributions 

to potential risk

4
OPTIONS FOR SCREENING

 USE LD50/ft2

 Easy

 Routinely done

 Doesn’t identify if drinking water, inhalation or dermal are 

specifically an issue (limits risk management options)

 Develop Screening Models for Each Exposure Route

 Minimal data needed

 Should be made to provide exposure modeling continuity 

with more complicated refinement levels

 Rely on other existing risk assessment tools

 Need to avoid RQ LOC adjustments

 Need to relate to oral dose effects data

5
GOALS FOR THE NEW MODELS

 Provide a transparent rationale for excluding 

inconsequential routes of exposure at the 

problem formulation stage of risk assessment

 Provide a transparent rationale for the 

recommendation of additional data needs at 

problem formulation specific to exposure routes 

of potential concern

 Rationale is based BOTH on exposure and 

effects considerations 

6
Version 1.0

Screening Imbibition Program

(SIP)

7
WHAT IS SIP V1.0?

INPUTS

 Qualitative Tool for PF to predict potential risk to birds and 

mammals via drinking water exposure.

 Inputs:

 Solubility

 Acute Avian and Mammalian LD50

 Chronic Avian NOAEC and Mammalian NOAEL

 Mineau Scaling Factor

 Test species

 Body Weights for species other than:

 Avian:

 Northern Bobwhite Quail

 Mallard Duck

 Mammalian:

 Laboratory Rat 8
ASSUMPTIONS

 The chemical is dissolved at the solubility limit in water 

(25 C). 

 Animals obtain 100% of their daily water needs through 

drinking water. 

 100% of the drinking water consumed by the assessed 

animal is at the chemical's solubility limit in water. 

 The daily water intake rate is equivalent to the daily water 

flux rate.

9
ASSUMPTIONS CON’T

 The body weight of the assessed bird for acute exposure is 

equivalent to the smallest generic bird modeled in T-REX (i.e., 20 

g). This results in the highest ratio of exposure to toxicity for the 3 

assessed avian body weights of T-REX (i.e., 20, 100, 1000 g). 

 The body weight of the assessed bird for chronic exposure is 

equivalent to the largest generic bird modeled in T-REX (i.e., 

1000 g). This results in the highest ratio of exposure to toxicity for 

the 3 assessed avian body weights of T-REX. 

 The body weight of the assessed mammal is equivalent to the 

largest generic mammal modeled in T-REX (i.e., 1000 g). This 

results in the highest ratio of exposure to toxicity for the 3 

assessed mammalian body weights of T-REX (i.e., 15, 35, 1000 

g). 

10
UPPER BOUND ESTIMATE OF EXPOSURE

 Total daily water intake rates used by TIM (based on Nagy and 

Peterson 1988). 

 Avian: (0.0162 L, assuming 20 g bird, 0.494 L, assuming 

1000 g bird)

 Mammalian: (0.172 L, assuming 1000 g mammal)

 Equation to determine high end dose (exposure):

(1.180* ) 1000 0.874 Fluxwater

= BW ÷

(0.708* ) 1000 0.795 Fluxwater

= BW ÷

BW

Flux Solubility Dose water

*

=

11
ADJUSTED ACUTE TOXICITY VALUES

( 1)

50

−





 



 =

x

TW

AW AT LD

 LD50 values are adjusted using the same approach employed by T-REX (USEPA 

2008) 

 Avian:

 Mammalian:

 Components / Units for the above equations are as follows:

 AT = adjusted toxicity value (mg/kg-bw).

 LD50 = endpoint reported by toxicity study (mg/kg-bw).

 TW = body weight of tested animal (350g rat; 1580g mallard, 178 g Northern bobwhite quail or 

other weight specified by user).

 AW = body weight of assessed animal. (20 g for bird, 1000 g for mammal).

 x = Mineau scaling factor. Chemical specific values for x may be located in the worksheet titled 

"Mineau scaling factors". If no chemical specific data are available, the default value of 1.15 

should be used for this parameter. 

( )

0.25

50 



 



 = AW

TW AT LD

12
13
ADJUSTED CHRONIC TOXICITY VALUES

( )

0.25





 



 = AW

TW AT NOAEL

 Chronic avian toxicity studies produce endpoints based on concentration in 

food, not dose. Therefore, these endpoints have to be converted. 

 Avian: Adjusted using the Wildlife Exposure Factors Handbook (USEPA 1993), FI = 

0.0582 kg-food for 1000 g bird.

 Mammalian: Adjusted using same approach employed in T-REX (USEPA 2008). If 

only NOAEC (in mg/kg-diet) is available, the NOAEC is divided by 20 (also 

employed in T-REX and relies on the standard FDA lab rat conversion).

BW

NOAEC FI Dose Equiv Toxicity* . = 0.651 FI = 0.0582*BW

14
WHAT IS TO COME?

 SIP v 2.0

 Will be a quantitative model used in Risk Assessment

 Will differentiate possible drinking water sources

 Dew

 Puddle

 Can be added into T-REX at a later date.

 Projected Release Date is Summer 2011

15
Version 1.0

Developed by Ed Odenkirchen and Joseph DeCant

Screening Tool for Inhalation Risk

(STIR)

16
MODEL OVERVIEW

 Estimates inhalation-type exposure and compares 

these estimates to avian and mammalian toxicity 

data. 

 Incorporates mammalian-oral, mammalian-inhalation, 

and avian-oral toxicity values from the literature.

 Problem formulation tool that assists chemical 

reviewers in assessing the need for further evaluation 

of inhalation risk to birds and mammals.

17
ROUTES OF EXPOSURE

Directly applied spray

Volatilization of residues on 

plant canopy

Volatilization of 

residues in soil

Suspension of residues 

associated with soil 

particulate







X

 addressed by screening 

tool

X not addressed

The Inhalation Route Conceptual Model

18
ASSUMPTIONS

Fate:

 Vapor pressure at 25oC and 1 atm

 Partial pressure at saturation

 Duration of exposure 

 Drift: 1.5 minutes aerial, 30 seconds ground

 Vapor: one hour vapor exposure

Effects:

 Use of a 0.02 kg bird, 0.015 kg mammal

 Allometric equation for inhalation based on non-passerine

 Avian Allometric equation based on oral toxicity

 Risk to only birds and mammals

19
CALCULATION OF EEC’S: SPRAY DROPLET 

CONCENTRATION

 Exposure based on:

 Method of application 

(spray or non-spray, 

ground or aerial)

 Application rate

















×

=

H 100

AR

Cair

Where:

Cair is in mg/cm3

AR = application rate in mg/cm2

H = height of spray column in m

100 = conversion from meters to centimeters

Assumed: Instantaneous mixing and release 

time

One Acre in Area

Ground Spray Applications: 1 m Aerial Applications: 3.3 m

Spray Height

20
SPRAY DROPLET INHALATION DOSE

60 AW

C IR D F

SID air inhaled

×

× × ×

=

Where:

SID = Spray droplet inhalation dose of assessed animal in mg/kg 

bwt

Cair = Air column concentration after spray in mg a.i./cm3

IR = Inhalation rate of assessed animal in cm3/hr 

D = Duration of direct spray inhalation (1.5 minutes for aerial and 

0.5 minutes for ground applications) 

Finhaled = Inhalable fraction of the spray distribution

AW = Body weight of assessed animal in kg

60 = Hours to minutes conversion

21
CALCULATION OF EEC’S: VAPOR CONCENTRATION

 The screening tool calculates the theoretical maximum pure 

product air concentration at 1 atm and 25 C

 Based on:

 Vapor pressure 

 Molecular weight

m

s 760 V

VP MW 1000 1000 C

×

× × ×

=

Where:

Cs = Air vapor concentration of a 

pesticide at saturation in mg/m3

VP = Vapor pressure in mm Hg 

MW = Molecular weight in g

Vm = Volume in liters (24.45 L/mol) 

occupied by 1 mol of a gas at a 

temperature of 25oC and pressure 

1atm according to the ideal gas law

22
VAPOR INHALATION DOSE

1000000 AW

C IR D

VID s

×

× ×

=

where:

VID = Vapor Inhalation Dose in mg/kg

Cs = saturated air concentration in mg/m3

IR = inhalation rate of assessed animal in cm3/hr

AW = body weight of assessed animal in kg 

D = duration of exposure, 1 hour

1,000,000 = conversion factor in cm3/m3

23
INHALATION TOXICITY

 2000 Scientific Advisory Panel advocated the need to assess 

inhalation toxicity as a route of exposure

 Mammalian Toxicity

 Guideline study – 870.1300 mammalian inhalation toxicity

 Avian Toxicity

 No established guideline study

 2004 Scientific Advisory Panel

 Established a method to extrapolate mammalian inhalation 

toxicity data to avian inhalation toxicity

 Extrapolation method based on relative diffusion rates in 

mammals and birds

 Define X

LD50 inhlation mammal = LD50 inhalation bird * X

LD50 oral mammal LD50 oral bird

24
FACTORS AFFECTING UPTAKE BY DIFFUSION

• Agency focus on surface area and exchange tissue thickness

• Other factors remain to be evaluated

- Cross current vs. alveolar systems and concentration gradient

Fick’s law of diffusion

Δ Q = -D*A*(Δ u/ Δ x)* Δ t

ΔQ - mass uptake,

D - chemical specific diffusion constant,

A - surface area of the diffusion site,

Δ u - concentration gradient,

Δ x - tissue thickness,

Δ t - duration of diffusion

25
RESPIRATORY SURFACE AREA

Respiratory surface area is 1.16 times 

greater in birds than mammals

Surface area birds = 60.6*BW0.883

Surface area mammals= 52.1*BW0.883

Maina et al. (1989)

26
EXCHANGE TISSUE THICKNESS

Avian exchange tissue thickness is from one 

half to one third mammal thickness for 

bodyweights 1 to 2000g

Mean harmonic thickness birds= 116.51*BW0.044 

Mean harmonic thickness mammals = 237.66*BW0.090

Maina et al. (1989)

27
RELATING AREA AND THICKNESS TO RELATIVE 

DIFFUSION RATE

 From Fick’s law diffusion rate is directly 

proportional to: Q = surface area / thickness

 Qavian/Qmammal ranges from 2.4 to 3.4 for 

bodyweights of 1 to 2000g

 For a given inhaled mass, birds will absorb 

more than mammals by at least a factor 

equivalent to Qavian/Qmammal

28
DEVELOPING A ROUTE RELATIVE POTENCY 

FACTOR

50avian oral

50avian inhalation

50mammaloral

50mammalinhalation

LD

LD X

LD

LD ×

=

50mammalinhalation

50mammaloral

LD

LD ( / ) Fe× Qa Qm

=

where, 

Fre = the avian inhalation route equivalency 

Qa/Qm = the ratio of avian to mammalian 

pulmonary membrane diffusion rates

Qa/Qm = X

Recall:

29
AVIAN INHALATION LD50

 The screening tool estimates a bird inhalation LD50 value (mg/kg- bw) by applying the relationship between mammalian oral and 

inhalation LD50 values to the most sensitive avian oral LD50 value. 

 3.5 = Qa/Qm = the ratio of avian to mammalian pulmonary 

membrane diffusion rates

50rat oral

50avian oral 50rat inhalation

50est 3.5 LD

LD LD

LD

×

×

=

30
ADJUSTED INHALATION ENDPOINTS

 The LD50 for both mammals and birds 

are adjusted to the body weight of a 

0.015 kg mammal and a 0.020 kg bird

 These body weights represent the most 

sensitive body weight in screening level 

assessments

0.25

mammal

mammal

50adj 50 AW

TW LD LD 















= ×

(x 1)

avian

avian

50adj 50 TW

AW LD LD

−

















= ×

where:

LD50adj in mg/kg-bw

AW = Body weight of assessed 

animal (0.015 kg rat, 0.020 kg 

bird) 

TW = Body weight of tested 

animal (e.g. 0.350 kg rat, 0.178 

kg Bobwhite quail)

All LD50 values are in mg/kg-bw

31
SAMPLE SCREEN SHOT OF STIR INPUT SECTION

Welcome to the EFED 

Screening Tool for Inhalation Risk

This tool is designed to provide the risk assessor with a rapid method for determining the potential

significance of the inhalation exposure route to birds and mammals in a risk assessment.

Input

Application and Chemical Information

Enter Chemical Name Chemical X

Enter Chemical Use

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) air

Enter Chemical Molecular Weight (g/mole) 350

Enter Chemical Vapor Pressure (mmHg) 5.50E+00

Enter Application Rate (lb a.i./acre) 0.012

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 12

Enter Mineau Scaling Factor 1.2

Enter Tested Bird Weight (kg) 1.58

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 440

Enter Lowest Rat Inhalation LC50 (mg/L) 0.1

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

**NOTE**: When entering values, press the "Enter" key in 

order to update linked cells.

32
RATIO

 Exposure / Toxicity

 Ratio ≥ 0.1 Pathway potentially significant

 Ratio < 0.1 Pathway likely not significant

 0.1  most conservative terrestrial animal LOC

*Tool does not calculate a risk quotient, nor does it 

estimate risk

33
SAMPLE SCREEN SHOT MODEL RESULTS

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 1.04E+05

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.30E+04

Adjusted Inhalation LD50 8.81E-03

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.48E+06 Proceed to Refinements

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.28E-03

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 1.45E-01 Proceed to Refinements

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m3) 1.04E+05

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.64E+04

Adjusted Inhalation LD50 5.95E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 2.75E+03 Proceed to Refinements

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.61E-03

Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD50 2.70E-04 Exposure not Likely Significant

34
PROBLEM FORMULATION CONSEQUENCES 

FOR CASES NOT PASSING STIR

 Step 1: Vapor or Droplet Phase

 Identify utility of an inhalation toxicity study for birds 

based on OPPTS Guideline 870.1300

 Step 2: Tier I Inhalation Risk Assessment

 Incorporation of refined exposure estimate using 

flux rate and dispersion model

 Comparison of refined exposure with available 

toxicity data

35
TIER 1 AIR EXPOSURE MODEL

36
EFED CONCEPTUAL MODEL FOR 

INHALATION EXPOSURE

Directly applied spray

Volatilization of 

residues on plant 

canopy

Volatilization of 

residues in soil

Suspension of residues 

associated with soil 

particulate





X 

addressed by proposed Tier 1 tool

X not addressed by proposed Tier 1 tool



addressed by proposed Tier 1 tool

X not addressed by proposed Tier 1 tool

37
VAPOR-PHASE MODEL SCENARIOS

 Bare Soil – On and Off-Field

 Vertical flux through soil coupled with downwind transport and dispersion in air at ground-level.

 Crops and Orchards - On-field

 Air concentrations are uniform and based on equilibrium plant residue and air concentration. 

Downwind transport and dispersion assumed small within plant canopy.

 Crops and Orchards - Off-field

 Vertical flux through crop canopy coupled with downwind transport above crop canopy and 

dispersion in air to ground-level.

Combinations 

of 

unidirectional 

wind vectors 

and 

turbulence

regimes

X x x

Bare Soil

x

Source Field Maximum concentration receptor

Crops

Combinations 

of 

unidirectional 

wind vectors 

and 

turbulence

regimes

X x x x

Off-field 

receptor

s

Maximum off-field

On concentration receptor -field ground-level 

concentrations assumed uniform

plume receptors plume

38
VAPOR-PHASE MODULES

Application 

Type

On-Field 

Module

Off-Field Module

Pre-Plant/ 

Pre-Emergent Soil

(FIFRA SAP, 2009)

Foliar Canopy/ 

Foliar Orchard

(FIFRA SAP, 2001) (FIFRA SAP, 2009)

Soil Volatile Flux

Woodrow et al., 

1997

Air 

Concentrations

SCREEN3 (Phase 1)

AERSCREEN (Phase 2)

Air 

Concentrations

Air-to-Plant Biotransfer 

Factor

Crop Canopy

Volatile Flux

Woodrow et al., 

1997

Air 

Concentrations

SCREEN3 (Phase 1)

AERSCREEN (Phase 2)

• Woodrow et al., 1997 – Upper-bound bare soil and crop canopy flux estimates 

from application rates and physical chemical properties.

• SCREEN3 and AERSCREEN – Atmospheric dispersion models from 

Office of Air estimate air concentrations using flux rates and meteorological data.

• Air-to-Plant Biotransfer Factor – Developed for the HWIR by the Office of Solid 

Waste, equilibrium air concentrations calculated based on Kow and app. Rate. 39
DIRECTLY APPLIED SPRAY

 Assessed at the screening level (STIR)

 Will also be considered at the Tier I level

 Instantaneous concentration based on loading within volume 

above treated field with depth set at the release height

Cair(drops) = Application rate / Release Height

where: 

release height = 3.3 m for aerial

release height = 1.0 m for ground

 Additional Considerations:

 Duration of exposure 

 Maximum size of respirable particle

 Off-field drift distance

40
Version 1.0

Developed by Ed Odenkirchen and Tanja Crk

Dermal Uptake Screening Tool

(DUST)

41
MODEL OVERVIEW

 Estimates dermal dose (i.e., exposure) and 

compares these estimates to mammalian and avian 

toxicity data (i.e., LD50). 

 Incorporates mammalian-acute dermal and avianacute oral toxicity values from the literature.

 Problem formulation tool that assists chemical 

reviewers in assessing the need for further 

evaluation of dermal exposure risk to mammals and 

birds (also amphibians & reptiles).

42
ROUTES OF EXPOSURE, REVISITED

Foliar spray •Aerial

•Ground

Bare ground spray

Granular

Upper 1⁄2 of body exposed

43
ASSUMPTIONS

1. Exposure to Birds and Mammals

 Bird ~ reptiles, amphibians 

2. Dermal exposure on field

3. Acute exposure

4. Smallest bird (20g) is most sensitive (applies to reptiles, amphibians)

5. Smallest mammal (15g) is most sensitive 

6. Soil density = 1.3 g/cm3 soil (standard assumption)

7. Soil depth = 1 cm

8. Foliar contact rate = 6.01 cm2 foliage/hr/cm2 body surface (Bradbury 2004, 

SAP; analogous to picker’s hands ≈ whole body contacting vegetation)

9. Soil to skin adherence factor = 0.958 mg/cm2 (EPA 2004, Superfund; 

analogous to commercial/industrial gardner’s hands ≈ mass of soil adhering to skin per unit 

of surface area)

10. Use t=0 dislodgeable foliar residue (DFR) from HED studies; when value 

not available assume 100% dislodgeability from foliage and application 

rate in mg/cm2

44
ASSUMPTIONS’

 100% absorption of pesticide through skin 

 Feathers of bird, scales of reptile, and hair of mammal do not limit exposure to skin (no such 

assumption for amphibians)

 Alternative: actual absorption depends on chemical properties

 100% availability of pesticide in environment

 Do not consider movement of pesticide from one compartment to another; what is applied 

comes directly in contact with the organism

 Alternative: availability of pesticide from soil governed by partitioning model linked to physical 

chemistry properties; mass of pesticide from foliage linked to crop type, age stage, and 

assumption of interception of application

 100% of body is exposed

 Alternative: Consider exposure to subset of the whole body (e.g. eyes or lower leg/foot)

 One application

 The amount of pesticide present in the environment is not dependent on dissipation of 

chemical over time – retention of dose in environment

 Alternative: account for dissipation of chemical over time in the environment (residue decline, 

dissipation from foliage) and metabolism of animal

45
ROUTES OF EXPOSURE: LINKED TO 

APPLICATION TYPE

Application Type 

(exposure equations)

50% of Body 

intercepts directly 

applied spray 

100% of Body 

intercepts foliar 

residue

100% of Body 

intercepts soil residue 

(dust, soil surface)

Foliar spray 

(aerial or ground)

X X

Granular X

Bare ground spray X X

Dermal dose = (application rate)(surface area)(fraction absorbed)

body weight 46
ROUTES OF EXPOSURE

 Foliar spray (aerial or ground)

 Contact with foliar residues and Directly applied spray

Symbol Parameter Description Units Notes

Dfoliar Dermal dose from foliar spray mg/kg-bw --

DFR Dislodgeable Foliar Residue mg/cm2 -@ t = 0

R’foliar contact Rate of foliar contact cm2foliage intercepted /

hour

-Equals: SAtotal* 6.01 cm2/hr/cm2

(i.e. hourly contact rate)

-Based on complete transfer of residues

-Assumption: 12 hour feeding period

Arate Application rate mg/cm2 --

SAtotal Total surface area of animal cm2

-Equals 10*BW0.667 (bird)

-Equals 12.3*BW0.65 (mammal)

-Equals: 8.42*BW0.694 (amphibian/reptile)

-Where BW is in g

-Assumption: Upper 1⁄2 of animal body is directly

exposed (spray); 100% exposed (foliage)

BW Body weight g -20g bird; 15g mammal

( /1000)

( ' *12) ( *0.5) Dfoliar

BW

DFR R foliarcontact +Arate SAtotal Exposure =

47
ROUTES OF EXPOSURE, CONT.

 Granular

 Contact with soil residues (dust and soil surface)

Symbol Parameter

Description Units / Values

S Surface Soil

Concentration mg a.i./ mg soil

Arate

application rate

from label mg/cm2

fsurface

Fraction of

concentration

assumed on

soil surface

1.00: unincorporated

0.15:chained in; lightly incorporated

0.01:side-dressed;in-furrow; drilled/

shanked

d Assumed depth 1 cm

ρsoil

Assumed soil

density 1.3 g soil /cm3 = 1300 mg soil /cm3

soil

Arate S

d *ρ

* fsurface

= Exposure

(dust bathing) BW/1000

* *

Dgranular

S fadherence SAtotal

=

Symbol Parameter

Description Units / Values

Dgranular

Dermal dose

from granular

applications

mg / kg-bw

fadherence

Soil to skin

adherence

factor

0.958 mg/cm2

SAtotal

Total surface

area of animal cm2

BW Body weight 20 g bird;

15 g mammal

48
ROUTES OF EXPOSURE, CONT.

 Bare ground spray

 Contact with soil residues (dust and soil surface) and Directly applied spray

Symbol Parameter Description Units Notes

Dground Dermal dose from bare ground spray mg/kg-bw --

S Surface soil concentration mg a.i./ mg soil -Equals (Arate * fsurface) / (d * ρsoil)

fadherence Soil to skin adherence factor mg/cm2 -Equals 0.958 mg/cm2

Arate Application rate mg/cm2 --

SAtotal Total surface area of animal cm2

-Equals 10*BW0.667 (bird)

-Equals 12.3*BW0.65 (mammal)

-Equals: 8.42*BW0.694 (amphibian/reptile)

-Where BW is in g

-Assumption: Upper 1⁄2 of animal body is directly

exposed (spray), 100% exposed (soil)

BW Body weight g -20 g bird; 15 g mammal

( / 1000)

* * ( * 0.5) Dground

BW

S fadherence SAtotal+Arate SAtotal

= Exposure

49
DERMAL TOXICITY DATA: 

BIRDS/REPTILES AND AMPHIBIANS

 None available for birds... Hence:

 Most sensitive avian acute oral endpoint

 Estimation of avian acute dermal LD50 (mg/kg-bw)*

* Based on peer reviewed approach presented to SAP 2004 (=Bradbury 2004 revision to Ch 3 of SAP)

 Scale to 20 g bird

(x-1) . 50( ) 50( )

*(20g/TW) Adj LD dermal = LD dermal

0.84 0.62*(log LD )

50( )

50(oral) 10 + LD dermal =

Birds/Reptiles LD50(dermal) < LD50(oral), when LD50(oral) >162.38

LD50(dermal) > LD50(oral), when LD50(oral) < 162.38

LD50(dermal) = LD50(oral), when LD50(oral) = 162.38

Amphibians 

LD50(dermal) ≈ LD50(oral)

50
DERMAL TOXICITY DATA: MAMMALS

 Data available from HED

 Most sensitive mammalian acute dermal LD50 (mg/kg-bw)

 Scale to 15 g mammal

(0.25)

50( ) 50( ) Adj.LD LD *(TW /15g) dermal = dermal

51
RATIO

 Exposure / Toxicity

 Ratio ≥ 0.1 Pathway potentially significant

 Ratio < 0.1 Pathway likely not significant

 0.1  most conservative terrestrial animal LOC

*Tool does not calculate a risk quotient, nor does it 

estimate risk

52
53
FOLLOW-UP ACTIONS FOR DUST

 Step 1: Voluntary data submission by registrant 

 Step 2: Tier I Dermal Exposure Risk Assessment

 Estimation of refined dermal dose (exposure)

 Direct acute dermal toxicity value for birds

 Comparison of refined exposure with available 

toxicity data (RQ calculation)

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SUMMARY OF APPLICATION OF THE SCREENING 

MODELS: INHALATION AND DERMAL

 Easy input Excel spreadsheet

 Scenarios are pre-built and selectable from pull- down menu

 Set up for specific use types

 Makes use of existing data

 Informs user of the need to move to next LOR 

(i.e., Tier I)

 Models automatically present:

 Calculated inhalation or dermal dose

 Decision to advance to next LOR or not

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FUTURE STEPS

TREX / 

THERPS

Screening Tools: SIP

Exposure Pathway: Drinking Water

STIR DUST

Inhalation Dermal Ingestion

Tier I Models:

Tier II Models: TIM

T o b e d e v e l o p e d

RQ calculation

Aggregation of pathways

ID data needs

Probabilistic 

Aggregation of pathways

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