The document summarizes proposed changes to the UK's Contaminated Land Exposure Assessment (CLEA) guidance. Key changes include updates to standard land use scenarios, exposure parameters, and plant uptake and indoor/outdoor vapor inhalation algorithms based on new scientific evidence. The proposed changes aim to improve the technical basis, consistency, clarity and usability of the CLEA model for deriving soil guideline values. A new CLEA report consolidating the guidance has been published, with additional updates planned over the next year.

1. Updating UK Risk Assessment Guidance Dr. Mengfang Chen, Technical Director

3. USEPA RAGS Tier 2 RBCA Toolkit ASTM E1739 Petroleum RBCA RBCA V1.0 ASTM 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 CLEA Plant Uptake Dermal Contact Indoor and Outdoor Vapours Probabilistic versus Deterministic Plant Uptake Vapour from Surface Soil Probabilistic versus Deterministic Plant Uptake Period of Development Period of Model Improvement and UK Compliance CLEA 97 CLEA UK CLEA V1.03 CLEA 2002 2008 CLEA V1.03 RBCA V1.3 ASTM E2081 Chemical RBCA CLEA RBCA History of CLEA Development

6. Exposure Duration and Averaging Time Changes in Standard Land Uses 17885 49 years (Age Class 17) Working Adult Commercial 2190 6 years Age Class (1 to 6) Younger Child Allotments 2190 6 years (Age Class 1 to 6) Younger Child Residential Averaging Time (days) Exposure Duration (years) Critical Receptor Standard Land Use

7. Exposure Frequencies Changes in Standard Land Uses Values in brackets are EF for ALLOTMENT where different from Resident Land use 170 230 170 230 - 230 17 (16 to 65) 365 (65) 365 (0) 365 (65) 365 (0) 365 365 (65) 6 (5 to 6) 365 (65) 365 (0) 365 (65) 365 (0) 365 365 (65) 5 (4 to 5) 365 (130) 365 (0) 365 (130) 365 (0) 365 365 (130) 4 (3 to 4) 365 (130) 365 (0) 365 (130) 365 (0) 365 365 (130) 3 (2 to 3) 365 (130) 365 (0) 365 (130) 365 (0) 365 365 (130) 2 (1 to 2) 365 (25) 365 (0) 180 (25) 180 (0) 180 180 (25) 1 (0 to 1) days /year Outdoor Inhalation Indoor Inhalation Dermal Outdoor Dermal Indoor Homegrown Produce Soil and Dust Ingestion Age Class (year)

8. Building Parameters Changes in Standard Land Uses 0.165 (0.1647) 0.04 (0.0423) m 2 Floor Crack Area 0.15 0.15 m Foundation Thickness 4.4 3.1 Pa Pressure Difference between Soil and Indoor Air 1.0 0.5 hour -1 Air Exchange Rate 6.4 (9.6) 4.8 m Living Space Height 424 28 m 2 Footprint Area Commercial (Three-Storey Pre 1970 Office) Residential (Two-Storey Small Terrace House) Unit Parameters

9. Consumption Rates and Home Grown Fractions Changes in Standard Land Uses 0.27 0.04 ( 0.22 ) 4.26 4.26 11.96 11.96 11.96 3.82 Tree Fruit 0.6 0.09 ( 0.35 ) 0.16 0.16 0.54 0.54 0.54 2.23 Shrub Fruit 0.4 0.06 ( 0.24 ) 1.85 1.85 3.96 3.96 3.96 1.83 Herbaceous Fruit 0.13 0.02 ( 0.12 ) 3.38 3.38 5.46 5.46 5.46 16.03 Tuber Vegetables 0.4 0.06 ( 0.38 ) 1.77 1.77 3.30 3.30 3.30 10.69 Root Vegetables 0.33 0.05 ( 0.39 ) 3.74 3.74 6.85 6.85 6.85 7.12 Green Vegetables Allotment Residential 5 to 6 4 to 5 3 to 4 2 to 3 1 to 2 0 to 1 Home Grown Fractions (HF) Consumption Rate (CR) (g FW kg -1 BW day -1 ) Vegetable Type

10. Key Exposure Parameters Changes in Standard Land Uses 14.8 0.7 8.3 50 160 70 17 (16 to 65) 12.2 (24.9) 1 (3) 19 100 110 19.7 6 (5 to 6) 12.2 (21.3) 1 (3) 19 100 100 16.9 5 (4 to 5) 12.2 (19.1) 1 (3) 23 100 90 15.1 4 (3 to 4) 12.7 (20.7) 1 (3) 23 100 90 12.7 3 (2 to 3) 13.3 (18.8) 1 (3) 23 100 80 9.8 2 (1 to 2) 8.5 (10.3) 1 (3) 23 100 70 5.6 1 (0 to 1) m 3 /day Hour d -1 Hour d -1 mg/d cm kg Daily Inhalation Rate (V inh ) Outdoor Site Occupancy Period (T site ) Indoor Site Occupancy Period (T site ) Soil and Dust Ingestion Rate Body Height (H) Body Weight (BW) Age Class (year)

11. Changes in Standard Land Uses Parameters Affecting Inhalation of Indoor and Outdoor Dust 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 100 0.7 0.8 120 Commercial - - 0.5 120 Allotment 60 0.7 0.75 2400 Residential µg m -3 g 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

12. Soil Parameters Changes in Standard Land Uses Effective air permeability is calculated using Equations A4 to A7 in Appendix A of the CLEA Report 7.54E-08 0.3509 0.1221 7.36E-03 0.07 0.54 0.24 0.3 1.18 Sand 3.05E-08 0.3201 0.0689 3.56E-03 0.12 0.53 0.33 0.2 1.21 Sandy Loam 1.05E-08 0.3078 0.0375 1.58E-03 0.18 0.58 0.440 0.14 1 Silt Loam 1.83E-08 0.3098 0.056 2.37E-03 0.15 0.53 0.37 0.16 1.2 Sandy Clay Loam 1.08E-08 0.3039 0.0437 1.51E-03 0.19 0.56 0.42 0.14 1.14 Clay Loam 7.28E-09 0.3072 0.0291 1.17E-03 0.21 0.58 0.5 0.1 1 Silty Clay Loam 7.18E-09 0.3155 0.0541 1.17E-03 0.26 0.63 0.51 0.12 0.94 Silty Clay 6.58E-09 0.2972 0.0385 9.93E-04 0.24 0.59 0.47 0.12 1.07 Clay dimensionless cm3 cm-3 cm 2 m  cm s -1 cm 3 cm -3 Total Water Air g cm -3 Effective Air Permeability van Genuchten Saturated Hydraulic Conductivity Residual Water Content Porosity Bulk Density Soil Type

13. New USEPA Method to Calculate Total Skin Surface Area Changes in Model Algorithms 476 ( 411 ) 476 ( 411 ) 0.08 0.08 1.785 160 70 16 to 65 873 ( 792 ) 688 ( 642 ) 0.33 0.26 0.794 110 19.7 5 to 6 822 ( 790 ) 657 ( 632 ) 0.35 0.28 0.704 100 16.9 4 to 5 742 ( 700 ) 593 ( 560 ) 0.35 0.28 0.636 90 15.1 3 to 4 620 ( 582 ) 485 ( 454 ) 0.32 0.25 0.582 90 12.7 2 to 3 533 ( 490 ) 420 ( 386 ) 0.33 0.26 0.484 80 9.8 1 to 2 366 ( 361 ) 297 ( 293 ) 0.32 0.26 0.343 70 5.6 0 to 1 cm 2 cm 2 - - Indoor Outdoor Indoor Outdoor m 2 cm kg Exposed Skin (SE in skin ) Exposed Skin (SE out skin ) Max Fraction of Exposed Skin (Φexp) Total Skin Surface Area (SA) Body Height (H) Body Weight (W) Age Class (year)

14. Preparation Factor (PF) – Soil Ingestion Attached to Vegetables Changes in Model Algorithms 0.6 0.001 0.157 Tree Fruit 0.6 0.001 0.166 Shrub Fruit 0.6 0.001 0.058 Herbaceous Fruit 1 0.001 0.21 Tuber Vegetables 1 0.001 0.103 Root Vegetables 0.2 0.001 0.096 Green Vegetables - (g g-1 FW) (g DW plant g-1 FW plant) Preparation Factor (PF) Soil Loading (SL) DW Conversion Factors (DW) Vegetable Type

15. Changes in Model Algorithms New Routine (USEPA Q/C) for Inhalation of Outdoor Vapours For Surface Soil (10 cm) USEPA 1996 Q/C Model For Subsurface Soil (>10 cm) ASTM 2000 (E2081) GQRA DQRA Mass Balance Approach

16. Changes for Inhalation of Indoor Vapours GQRA DQRA Case A (  d > ED) Case B (  d < ED) Mass Balance Changes in Model Algorithms Calculating time for source depletion 65 (including 15 cm foundation thickness) cm Depth to Top of Source 300 50 cm 3 s -1 Soil Gas Ingress Rate Commercial (Post 1970 Office + Sandy Soil) Residential (Detached House + Sandy Soil) Unit Parameters

17. Changes in Model Algorithms Complete New Plant Uptake Algorithms 35 Additional Plant Properties Introduced 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 Potatoes Tuber Vegetables Apples, apricot, cherries, peaches, pears and plums Tree 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 INCLUDED PRODUCE GROUP

18. Complete New Plant Uptake Algorithms Organic Compounds Inorganic Compounds Changes in Model Algorithms

19. Complete New Plant Uptake Algorithms Changes in Model Algorithms Introduction of New Cross-Media Coefficients and Concentrations Descriptions Unit Symbol Chemical Concentration in the Woody Stem mg cm -3 per mg g -1 C stem Chemical Concentration in Xylem Sap mg cm -3 per mg g -1 C xy Wood Water Partition Coefficients mg g -1 dw wood per mg cm -3 water K wood Rate of Chemical Flux into Potato Hour -1 k 1 Rate of Chemical Flux Out of Potato Hour -1 k 2 Diffusion Coefficients in Water m 2 s -1 Dw Equilibrium Partition Coefficient between Potato and Water cm 3 g -1 fw K pw Carbonhydrate-Water Partition Coefficients cm 3 g -1 fw K ch Equilibrium Partition Coefficient between Root and Water cm 3 g -1 fw K rw Soil Leachate Partition Factor kg/l K sw Plant Media Transfer Coefficients and Concentrations

20. Complete New Plant Uptake Algorithms Inorganic Compounds Changes in Model Algorithms 0.5 Tree Fruit 0.5 Shrub Fruit 0.5 Herbaceous Fruit 0.5 Tuber Vegetables 0.5 Root Vegetables 0.5 Green Vegetables Fraction of chemicals in root system reaching edible plant plants (f int ) Vegetable Type 50 Selenium 5 Mercury 5 Chromium 5 Cadmium 5 Arsenic  Soil to Plant Availability Correction Contaminant

21. Complete New Plant Uptake Algorithms Organic Compounds – Green Vegetable Changes in Model Algorithms Only Routine Retained from CLR10 (CLEA2002) CLEA UK

22. Complete New Plant Uptake Algorithms Organic Compounds – Root Vegetable Changes in Model Algorithms Correction Coefficients for Roots - b Density Correction Factor between Water and Octanol - a Root Lipid Content g g -1 L Root Water Content g g -1 W First Order Metabolism Rate Constant d -1 k m First Order Growth Rate Constant d -1 k g Root Volume cm 3 V Plant Root Density g fw/cm 3  p Transpiration Stream Flow Rate cm 3 d -1 Q Descriptions Unit Symbol

23. Complete New Plant Uptake Algorithms Organic Compounds – Tuber Vegetable Changes in Model Algorithms Descriptions Unit Symbol Radius of Potato m R Exponential Rate of Growth of Potato hour -1 k g Correction Coefficients for Roots - b Density Correction Factor between Water and Octanol - a Lipid Content of Potato g g -1 L Fraction of Carbonhydrates in the Potato - F ch Plant Tuber Density g/cm 3  p Water Content of Potato g g -1 W

24. Complete New Plant Uptake Algorithms Organic Compounds – Tree Fruit Changes in Model Algorithms Descriptions Unit Symbol Dry Matter Content of Fruit g g -1 DM fruit Water Flow Rate per Unit of Mass of Fruit cm 3 g -1 fw Q fruit Mass of Fruit g fw M f Rate of Dilution due to Wood Growth year -1 k g Rate of Chemical Metabolism year -1 k e Mass of Woody Stem g dw M Transpiration Stream Flow Rate cm 3 d -1 Q

25. Summary of CLEA Testing

26. Summary of CLEA Testing Equation 9.6 Indoor Dust Equation 10.2 Outdoor Vapour

27. Summary of CLEA Testing

28. Way Forward Comparison of RBCA V2 and CLEA V1.03 beta

29. Thank you for your attention