# 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 LD 50 

# /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 LD 50  

### 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): 

# ( **)** 1000 * 180 . 1 874 . 0 

## ÷ **=** BW Flux water 

# ( **)** 1000 * 708 . 0 795 . 0 

## ÷ **=** BW Flux water


## BW ility lub So Flux Dose water 

## * **=** 11

# ADJUSTED ACUTE TOXICITY VALUES
**( )**  1 50 **− **  ** **  ** **  ** =**  x TW AW LD AT  

### LD 50 

### 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).  LD 50 = 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. 

## ( **)** 25 . 0 50 

###  ** **  ** **  ** =**  AW TW LD AT

1213

# ADJUSTED CHRONIC TOXICITY VALUES

**( )**  25 . 0 ** **  ** **  ** **  **=** AW TW NOAEL AT  

### 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 FI NOAEC Toxicity Equiv Dose *

. **=** 651 . 0 

### * 0582 . 0 BW FI **=**

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 

#  ** **  ** **  ** **  ** ×**  **=** 100 H AR C air 

### Where: C air 

### is in mg/cm 3 

### AR = application rate in mg/cm 2 

### 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 AW 60 F D IR C SID inhaled air 

# × **× ×**  **× =**  Where: SID = Spray droplet inhalation dose of assessed animal in mg/kg bwt C air 

### = Air column concentration after spray in mg a.i./cm 3 

### IR = Inhalation rate of assessed animal in cm 3

### /hr D = Duration of direct spray inhalation (1.5 minutes for aerial and 0.5 minutes for ground applications) F inhaled 

### = 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 

# V 760 1000 1000 MW VP C **× ×**  **× ×**  **=** Where: C s 

### = Air vapor concentration of a pesticide at saturation in mg/m 3 

### VP = Vapor pressure in mm Hg MW = Molecular weight in g V m 

### = 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 AW 1000000 D IR C 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 cm 3

### /m 3
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  

# Q avian

# /Q mammal 

# 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 Q avian

# /Q mammal

28

# DEVELOPING A ROUTE RELATIVE POTENCY FACTOR

oral 50avian inhalation 50avian oral 50mammal inhalation 50mammal 

# LD X LD LD LD **× =**  inhalation 50mammal oral 50mammal 

# LD ) / ( LD Fe m a 

# Q Q **× =**  where, F re 

## = the avian inhalation route equivalency Q a

## /Q m 

## = 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 LD 50 

## value (mg/kg- bw) by applying the relationship between mammalian oral and inhalation LD 50 

## values to the most sensitive avian oral LD 50 

## value.  

## 3.5 = Qa/Qm = the ratio of avian to mammalian pulmonary membrane diffusion rates oral rat 50 inhalation rat 50 oral avian 50 est 50 

# LD 3.5 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 50 50adj 

# AW TW LD LD ** **  ** **  ** **  ** **  **× =**  **( )**  1 x avian avian 50 50adj 

# TW AW LD LD **−** 

#  ** **  ** **  ** **  ** ×**  **=**
where: LD 50

### adj 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 LD 50 

### 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 LD 50(mg/kg bw) 12 Enter Mineau Scaling Factor 1.2 Enter Tested Bird Weight (kg) 1.58 **Mammal** Enter Lowest Rat Oral LD 50(mg/kg bw) 440 Enter Lowest Rat Inhalation LC 50(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/m 3) 1.04E+05 Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.30E+04 Adjusted Inhalation LD 50 8.81E-03 Ratio of Vapor Dose to Adjusted Inhalation LD 50 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 LD 50 1.45E-01 Proceed to Refinements Results Mammalian (0.015 kg ) Maximum Vapor Concentration in Air at Saturation (mg/m 3) 1.04E+05 Maximum 1-hour Vapor Inhalation Dose (mg/kg) 1.64E+04 Adjusted Inhalation LD 50 5.95E+00 Ratio of Vapor Dose to Adjusted Inhalation LD 50 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 LD 50 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 concentration receptor On -field ground - level concentrations assumed uniform plume plume receptors

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 ., LD 50

# ).  

# Incorporates mammalian -acute dermal and avian acute 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/cm 3 

### soil (standard assumption) 7. 

### Soil depth = 1 cm 8. 

### Foliar contact rate = 6.01 cm 2 

### foliage/hr/cm 2 

### body surface (Bradbury 2004, SAP; analogous to picker’s hands ≈ whole body contacting vegetation ) 9. 

### Soil to skin adherence factor = 0.958 mg/cm 2 (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/cm 2
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 D foliar Dermal dose from foliar spray mg/kg - bw -- DFR Dislodgeable Foliar Residue mg/cm 2 - @ t = 0 R’ foliar contact Rate of foliar contact cm 2foliage intercepted / hour - Equals : SA total * 6 . 01 cm 2 /hr/cm 2 (i . e . hourly contact rate)

- Based on complete transfer of residues

-Assumption : 12 hour feeding period Arate Application rate mg/cm 2 -- SA total Total surface area of animal cm 2 - 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 - 20 g bird ; 15 g mammal 

## ) 1000 / ( ) 5 . 0 * ( ) 12 * ' ( D foliar 

## BW SA A R DFR total rate act foliarcont 

## + **=** 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 A rate application rate from label mg/cm 2 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 **ρ** soil Assumed soil density 1 . 3 g soil /cm 3 = 1300 mg soil /cm 3 soil rate 

# A S **ρ** * d f * surface 

# = Exposure (dust bathing) 

## BW/1000 * * D granular total adherence 

## SA f S **=** Symbol Parameter Description Units / Values D granular Dermal dose from granular applications mg / kg - bw fadherence Soil to skin adherence factor 0 . 958 mg/cm 2 SA total Total surface area of animal cm 2 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 D ground Dermal dose from bare ground spray mg/kg - bw -- S Surface soil concentration mg a . i ./ mg soil - Equals (A rate * fsurface) / (d * **ρ** soil ) fadherence Soil to skin adherence factor mg/cm 2 - Equals 0 . 958 mg/cm 2 Arate Application rate mg/cm 2 -- SA total Total surface area of animal cm 2 - 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 / ( ) 5 . 0 * ( * * D ground 

## BW SA A SA f S total rate total adherence 

## + **=** 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 LD 50 

### (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 1) - (x ) ( 50 ) ( 50 g/TW) 20 ( * . dermal dermal LD LD Adj **=** ) LD *(log 0.62 0.84 ) ( 50 50(oral) 

### 10 **+** 

### = dermal 

### LD Birds/Reptiles LD 50(dermal) < LD 50(oral), when LD 50(oral) >162.38 LD 50(dermal) > LD 50(oral), when LD 50(oral) < 162.38 LD 50(dermal) = LD 50(oral), when LD 50(oral) = 162.38 

### Amphibians LD50(dermal) 

### ≈ LD 50(oral)

50

# DERMAL TOXICITY DATA: MAMMALS  

# Data available from HED  

### Most sensitive mammalian acute dermal LD 50 

### (mg/kg- bw)  

### Scale to 15 g mammal (0.25) ) ( 50 ) ( 50 

## ) 15 / ( * . g TW LD LD Adj 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

5253

# 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)

54

# 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
55

# FUTURE STEPS

TREX / THERPS Screening Tools: SIP Exposure Pathway: Drinking Water STIR DUST Dermal Inhalation 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 56