Updating UK Risk Assessment Guidance
Dr. Mengfang Chen, Technical Director
Outline
Review of CLEA Development
New Guidance Just Published and Forthcoming
Changes in Standard Land Uses
Changes in Model Algorithms
Results of CLEA Testing
Potential Impact on the Published SGV
USEPA RAGSTier 2 RBCA Toolkit
ASTM E1739Petroleum RBCA
RBCA V1.0ASTM P104
Chemical RBCA
Marked the Start of CLEA
CLEA 97 CLEA2000 CLEA2002 CLEA UK CLAN6/06
1989 1996 1999
1992 1997 2000 2002 2005 2006
Period of Development and Debate, and Continuing
2008
RBCA V2.01
2000
RBCA
CLEAPlant Uptake
Dermal ContactIndoor and Outdoor Vapours
Probabilistic versus Deterministic
Plant UptakeVapour from Surface Soil
Probabilistic versus Deterministic
Plant Uptake
Period of Development Period of Model Improvement and UK Compliance
CLEA 97 CLEA UK CLEA V1.03CLEA 2002
2008
CLEA V1.03
RBCA V1.3ASTM E2081
Chemical RBCA
CLEA
RBCA
History of CLEA Development
CLEA Report (Based on CLAN6/06 Way Forward November 2006)
Consolidation of technical guidance on the CLEA model into a single report focussed on the derivation of SGVs with improved readability and accessibility
Update of the date sets and model algorithms used in the CLEA model based recent scientific literature
Reconsideration of the generic land use scenarios default assumptions used in the CLEA model to derive SGVs including improvements in clarity, internal consistency, and practical usability of the approach.
Updating and Replacing CLR10 and CLEA Briefing Notes 1 to 4
New Guidance JUST Published and Forthcoming
CLEA 97 CLEA UK CLEA V1.03CLEA 2002
New Guidance JUST Published and Forthcoming
Just Published
CLAIRE and CIEH (Replacing CLR7??) – May 2008
CLEA Report (replacing CLR10) – August 2008
CLEA V1.03 beta and Software Handbook – August 2008
TOX Guidance Report (Replacing CLR9) – August 2008
Compilation of Data for Priority Organic Pollutants for the derivation of SGV – November 2008
Forthcoming (Updating TOX and SGV reports) – By March 2009
Arsenic, Cadmium, Chromium, Cyanide, Lead, Mercury, Nickel, and Selenium
Benzene, Toluene, Ethylbenzene, Xylene
Phenol
Dioxins and Dioxin-like Polychlorinated Biphenyls (PCBs);
Polycyclic Aromatic Hydrocarbons (PAHs) – 11 substances
1788549 years
(Age Class 17)Working AdultCommercial
21906 years
Age Class (1 to 6)
Younger ChildAllotments
21906 years
(Age Class 1 to 6)
Younger ChildResidential
Averaging Time (days)
Exposure Duration (years)
Critical Receptor
Standard Land Use
Exposure Duration and Averaging Time
Changes in Standard Land Uses
Exposure Frequencies
170230170230-23017 (16 to 65)
365 (65)365 (0)365 (65)365 (0)365365 (65)6 (5 to 6)
365 (65)365 (0)365 (65)365 (0)365365 (65)5 (4 to 5)
365 (130)365 (0)365 (130)365 (0)365365 (130)4 (3 to 4)
365 (130)365 (0)365 (130)365 (0)365365 (130)3 (2 to 3)
365 (130)365 (0)365 (130)365 (0)365365 (130)2 (1 to 2)
365 (25)365 (0)180 (25)180 (0)180180 (25)1 (0 to 1)
days /year
Outdoor Inhalation
Indoor Inhalation
Dermal Outdoor
Dermal Indoor
Homegrown Produce
Soil and Dust IngestionAge Class
(year)
Changes in Standard Land Uses
Values in brackets are EF for ALLOTMENT where different from Resident Land use
Building Parameters
0.165 (0.1647)0.04 (0.0423)m2Floor Crack Area
0.150.15mFoundation Thickness
4.43.1PaPressure Difference between Soil and Indoor Air
1.00.5hour-1Air Exchange Rate
6.4 (9.6)4.8mLiving Space Height
42428m2Footprint Area
Commercial (Three-Storey Pre 1970 Office)
Residential (Two-Storey Small Terrace House)
UnitParameters
Changes in Standard Land Uses
Consumption Rates and Home Grown Fractions
0.270.04 (0.22)4.264.2611.9611.9611.963.82Tree Fruit
0.60.09 (0.35)0.160.160.540.540.542.23Shrub Fruit
0.40.06 (0.24)1.851.853.963.963.961.83Herbaceous Fruit
0.130.02 (0.12)3.383.385.465.465.4616.03Tuber Vegetables
0.40.06 (0.38)1.771.773.303.303.3010.69Root Vegetables
0.330.05 (0.39)3.743.746.856.856.857.12Green Vegetables
AllotmentResidential5 to 64 to 53 to 42 to 31 to 20 to 1
Home Grown Fractions (HF)
Consumption Rate (CR) (g FW kg-1 BW day-1)Vegetable Type
Changes in Standard Land Uses
Key Exposure Parameters
14.80.78.3501607017 (16 to 65)
12.2 (24.9)1 (3)1910011019.76 (5 to 6)
12.2 (21.3)1 (3)1910010016.95 (4 to 5)
12.2 (19.1)1 (3)231009015.14 (3 to 4)
12.7 (20.7)1 (3)231009012.73 (2 to 3)
13.3 (18.8)1 (3)23100809.82 (1 to 2)
8.5 (10.3)1 (3)23100705.61 (0 to 1)
m3/dayHour d-1Hour d-1mg/dcmkg
Daily Inhalation Rate (Vinh)
Outdoor Site Occupancy Period (Tsite)
Indoor Site Occupancy Period (Tsite)
Soil and Dust
Ingestion Rate
Body Height (H)
Body Weight (BW)
Age Class (year)
Changes in Standard Land Uses
Changes in Standard Land Uses
Parameters Affecting Inhalation of Indoor and Outdoor Dust
1000.70.8120Commercial
--0.5120Allotment
600.70.752400Residential
µg m-3g g-1-g.m-2.s-1/kg.m-3
Soil Loading Factor (SL)
Transport Factor (TL)
Fraction of Vegetative and Buildings (V)
Air Dispersion Coefficient (Q/C)Land Use
Q/C default values were taken from Newcastle
representing areas of 0.01, 0.5 and 2 Ha
Respectively for residential, allotment and
commercial land uses
TL and SL used to calculate
intake rate for inhalation of indoor dust
Soil Parameters
7.54E-080.35090.12217.36E-030.070.540.240.31.18Sand
3.05E-080.32010.06893.56E-030.120.530.330.21.21Sandy Loam
1.05E-080.30780.03751.58E-030.180.580.4400.141Silt Loam
1.83E-080.30980.0562.37E-030.150.530.370.161.2Sandy Clay Loam
1.08E-080.30390.04371.51E-030.190.560.420.141.14Clay Loam
7.28E-090.30720.02911.17E-030.210.580.50.11Silty Clay Loam
7.18E-090.31550.05411.17E-030.260.630.510.120.94Silty Clay
6.58E-090.29720.03859.93E-040.240.590.470.121.07Clay
dimensionlesscm3 cm-3cm2
mαcm s-1cm3 cm-3
TotalWaterAirg cm-3
Effective Air Permeability
van GenuchtenSaturated Hydraulic
Conductivity
Residual Water Content
PorosityBulk
DensitySoil Type
Changes in Standard Land Uses
Effective air permeability is calculated using Equations A4 to A7 in Appendix A of the CLEA Report
New USEPA Method to Calculate Total Skin Surface Area 51456.042246.00235.0 BWHSA ××=
476 (411)476 (411)0.080.081.7851607016 to 65
873 (792)688 (642)0.330.260.79411019.75 to 6
822 (790)657 (632)0.350.280.70410016.94 to 5
742 (700)593 (560)0.350.280.6369015.13 to 4
620 (582)485 (454)0.320.250.5829012.72 to 3
533 (490)420 (386)0.330.260.484809.81 to 2
366 (361)297 (293)0.320.260.343705.60 to 1
cm2cm2--
IndoorOutdoorIndoorOutdoorm2cmkg
Exposed Skin (SEin
skin)Exposed Skin
(SEoutskin)
Max Fraction of Exposed Skin (Φexp)
Total Skin Surface Area
(SA)
Body Height
(H)
Body Weight
(W)Age Class (year)
Changes in Model Algorithms
90BW
7BW)(4AT +
+×=
Preparation Factor (PF) – Soil Ingestion Attached to Vegetables
Changes in Model Algorithms
0.60.0010.157Tree Fruit
0.60.0010.166Shrub Fruit
0.60.0010.058Herbaceous Fruit
10.0010.21Tuber Vegetables
10.0010.103Root Vegetables
0.20.0010.096Green Vegetables
-(g g-1 FW)(g DW plant g-1 FW plant)
Preparation Factor (PF)
Soil Loading (SL)
DW Conversion Factors (DW)
Vegetable Type
( )∑=
×××××=TypeVegofNo
iiiiiii
soil
SLPFDWHFBWCRC
IR ___
1
Changes in Model Algorithms
New Routine (USEPA Q/C) for Inhalation of Outdoor Vapours
41031536000
4
/
10 ××
×××
××=ssw
ambeff
wind
s
K
HD
CQVF
ρτπρFor Surface Soil (10 cm)
USEPA 1996 Q/C Model
For Subsurface Soil (>10 cm)
ASTM 2000 (E2081)aw
sw
eff
wind
KK
D
gkgmcmcmmCQVF
××××
+
=−−−− 13322
10001
1000000100001
/1
1
GQRA
DQRA
τρ
××=wind
ss
CQ
dVF
/Mass Balance Approach
Changes for Inhalation of Indoor Vapours
GQRA
DQRA
Case A (τd > ED)
Case B (τd < ED)
Mass Balance
65 (including 15 cm foundation thickness)cmDepth to Top of Source
30050cm3 s-1Soil Gas Ingress Rate
Commercial (Post 1970 Office + Sandy Soil)
Residential (Detached House + Sandy Soil)
UnitParameters
Changes in Model Algorithms
33610 −××
××= mcmQ
AdVF
b
bss
τρ
( )( )βϕτβτ
ρ −+
×
××= 22
s
T
b
bss
d
L
Q
AdVF
ϕ
ββτ
2
2
2
−
+
= T
s
d
L
d
Calculating time for source depletion
Changes in Model Algorithms
Complete New Plant Uptake Algorithms
Beetroot, carrot, cassava, garlic, ginger, Jerusalem artichoke, leek, onion, parsnips, radish, rhubarb, salsify, swede, sweet potato, turnips and yam
Root Vegetables
Aubergine, courgettes, cucumber, marrow, pumpkin, strawberries and tomatoes Herbaceous Fruit
PotatoesTuber Vegetables
Apples, apricot, cherries, peaches, pears and plumsTree Fruit
Bilberries, blackberries, cranberries, gooseberries, loganberries, mulberries, physalis, raspberries, blackcurrants, redcurrants and white currants
Shrub Fruit
Beans (broad, French, green and runner beans), cabbage (red, white, greens and kale), cauliflower, lettuce, spinach, peas (garden and mange tout), stem vegetables (broccoli, celery, asparagus), okra, global artichokes, Chinese leaves, endives, chicory, chard, dandelion, watercress and fresh herbs (basil, coriander, tarragon, sage, parsley and mint)
Green Vegetables
CROPS INCLUDEDPRODUCE GROUP
35 Additional Plant Properties Introduced
Complete New Plant Uptake Algorithms
Organic Compounds
Inorganic Compounds
Changes in Model Algorithms
Complete New Plant Uptake Algorithms
Changes in Model Algorithms
DescriptionsUnitSymbol
Chemical Concentration in the Woody Stemmg cm-3 per mg g-1Cstem
Chemical Concentration in Xylem Sapmg cm-3 per mg g-1Cxy
Wood Water Partition Coefficientsmg g-1 dw wood per mg cm-3 waterKwood
Rate of Chemical Flux into PotatoHour-1k1
Rate of Chemical Flux Out of PotatoHour-1k2
Diffusion Coefficients in Waterm2 s-1Dw
Equilibrium Partition Coefficient between Potato and Watercm3 g-1 fwKpw
Carbonhydrate-Water Partition Coefficientscm3 g-1 fwKch
Equilibrium Partition Coefficient between Root and Water cm3 g-1 fwKrw
Soil Leachate Partition Factorkg/lKsw
Plant Media Transfer Coefficients and Concentrations
Introduction of New Cross-Media Coefficients and Concentrations
Complete New Plant Uptake Algorithms
Inorganic Compounds
Changes in Model Algorithms
intfKCR
dws
×+
=ρθ
δ
0.5Tree Fruit
0.5Shrub Fruit
0.5Herbaceous Fruit
0.5Tuber Vegetables
0.5Root Vegetables
0.5Green Vegetables
Fraction of chemicals in root system reaching edible plant plants (fint)
Vegetable Type
50Selenium
5Mercury
5Chromium
5Cadmium
5Arsenic
δ
Soil to Plant Availability CorrectionContaminant
Complete New Plant Uptake Algorithms Organic Compounds – Green Vegetable
Changes in Model Algorithms
( )
+
×+= −−−
ococsw
sKKGreen fK
CF owow
ρθρ
)10784.0(82.010 44.2/)78.1(log434.005.2log95.0 2
Only Routine Retained from CLR10 (CLEA2002)
ρθρθ aococw
swHfK
K++=CLEA UK
Complete New Plant Uptake Algorithms Organic Compounds – Root Vegetable
Changes in Model Algorithms
( )( ) Vkk
KQ
KQCF
pmgrw
dRoot
ρ++= /
bow
pprw aK
LWK
ρρ+=
Correction Coefficients for Roots-b
Density Correction Factor between Water and Octanol-a
Root Lipid Contentg g-1L
Root Water Contentg g-1W
First Order Metabolism Rate Constantd-1km
First Order Growth Rate Constantd-1kg
Root Volumecm3V
Plant Root Densityg fw/cm3ρp
Transpiration Stream Flow Ratecm3 d-1Q
DescriptionsUnitSymbol
Complete New Plant Uptake Algorithms Organic Compounds – Tuber Vegetable
Changes in Model Algorithms
ρθρθ aococw
swHfK
K++=
bow
pchch
ppw aK
LKf
WK
ρρ++= )(
=
sw
pw
K
Kkk 21
2
3/7
2
)/(360023
R
K
WD
Kpw
pw
=
ρ
gTuber kk
kCF
+=
2
1
DescriptionsUnitSymbol
Radius of PotatomR
Exponential Rate of Growth of Potatohour-1kg
Correction Coefficients for Roots-b
Density Correction Factor between Water and Octanol-a
Lipid Content of Potatog g-1L
Fraction of Carbonhydrates in the Potato-Fch
Plant Tuber Densityg/cm3ρp
Water Content of Potatog g-1W
Complete New Plant Uptake Algorithms Organic Compounds – Tree Fruit
Changes in Model Algorithms
owwood KLogK log632.027.0 +−= 58.2
)5.2(log 2
756.0−−
=
owK
sw
sxy e
K
CC
gewood
xy
stem
kkMK
QM
QC
C++
=
s
fwood
stemfruitfruitf
TreeFruit C
MKC
DMQM
CF
/)(
=
DescriptionsUnitSymbol
Dry Matter Content of Fruitg g-1DMfruit
Water Flow Rate per Unit of Mass of Fruitcm3 g-1 fwQfruit
Mass of Fruitg fwMf
Rate of Dilution due to Wood Growthyear-1kg
Rate of Chemical Metabolismyear-1ke
Mass of Woody Stemg dwM
Transpiration Stream Flow Ratecm3 d-1Q
Summary of CLEA Testing
Summary of CLEA Testing
ssw
ambeff
wind
s
K
HD
CQVF
ρτπρ
××
×××
×=
31536000
4
/101
Equation 9.6
Indoor Dust
Equation 10.2
Outdoor Vapour
( )
××
××+×
×= −
241000
1 1 siteinhss
TVDLTFCKgg
PEFCIR
( ) 1100024
1 −×
××
××+
×= Kgg
TVDLTFC
PEFCIR site
inhss
ssw
ambeff
wind
s
K
HD
CQVF
ρτπρ
××
×××
=31536000
4
/
Summary of CLEA Testing
Way Forward
Comparison of RBCA V2 and CLEA V1.03 beta
Thank you for your attention
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