adaptation of the dream tool
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DESCRIPTIONA presentation given at X2012 as part of a session on the GuLF study.
- 1.WORKING FOR A HEALTHY FUTUREDevelopment of the DREAM model for dermalexposure assessment of oil clean-up workersin the GuLF STUDY Melanie Gorman Ng1, John W Cherrie1, Mark Stenzel2, Richard Kwok3, Berna van Wendel de Joode4, Patricia Stewart51 Institute of Occupational Medicine2 Exposure Assessment Applications, LLC3 National Institute of Environmental Health Sciences4 Universidad Nacional de Costa Rica5 Stewart Exposure Assessments, LLCINSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UKwww.iom-world.org
2. GuLF STUDY Dermal ExposureOver 150,000 air measurementsNo dermal or surface contamination measurementsNeed to assess dermal exposure to: Oil Residues, (e.g.. VOCs, PAHs, BTEX) Dispersants (e.g. 2-butosyethanol, propylene glycol)2 3. DREAM Develop estimates from taskdescriptive information Estimates are reproduciblebetween assessors Estimates exposure inDream Units - DU Validation study showedreasonable correlation withmeasurement datavan Wendel de Joode et al. Accuracy of a semiquantitative method for Dermal 3Exposure Assessment (DREAM). Occup Environ Med (2005) vol. 62 (9) pp. 623-32 4. Challenges for GuLF STUDYPoor precision when range of exposure levels is small (less than half an order of magnitude)Does not take into account many factors that may be important (e.g. heat, use of sun screen, insect repellents, etc)Model is ten years old and based on limited data4 5. DREAMExposure Assessors estimate exposure from each ofthe three pathways of dermal exposure: Immersion Surface Contact Deposition Number of Skin area Substance exposure events exposed characteristicsFrequency x Intensity x Intrinsic Emission DermalExposure =ClothingProtectionFactor 5 6. Updating DREAMUpdate/review literature on model parameters relevant to GuLF STUDY: viscosity and stickiness evaporation gloves and protective clothing seawater and sweat sun screens & insect repellentsAmend other variables as necessary based on recent literature6 7. Major updates -PPEAvailable biomonitoring studies suggest gloves are less effective than DREAM had previously assumed E.g. Pesticide applicators: 90% vs. 40% (Brouwer and van Hemmen, 1997) E.g. Creosote workers: 60% vs. 50% reduction in 1- hydroxy-pyrene (vam Rooij et al, 1993)Brouwer and van Hemmen (1997). Brighton Crop Protection Conference: 1059-65. 7van Rooij et al (1993) Scand J Work Envir Hlth; 19:200-7 8. Major Updates - EvaporationOriginal DREAM Based onBoiling point150C = 10GuLF DREAM uses equations used in IHSkinPerm and NIOSH Skin Permeation Calculator (Kasting and Miller, 2006)6320 V 0.78 VP MW EvaporationRate =0.76 R T 3 MWKasting and Miller (2006). Kinetics of finite dose absorption through skin 2: VolatileCompounds. J Pharm Sci; 95(2):268-280. 8 9. Major Updates - EvaporationRatio Highest to Lowest Expected Evaporation RateExamined change in600evaporation rate over 500500expected range400300holding other 200parameters constant 1000 1.67 11 1.1Vapour Pressure Molecular Weight Wind Speed Temperature Developed DREAM multipliers within expected range9 10. Major Updates Exposure Pathway Skin exposure less likely to be correlated with air GMconcentration when workers also exposed to 7821contaminated surfaces (Burstyn et al, 2002; g/cm2Pronk et al, 2006; Links et al, 2007) GM 0.6 g/ cm2Also included different effect ofviscosity by exposure pathway: GM Exposure increases with 0.22viscosity but effect is strongest g/cm2for immersion 10 11. Comparison DREAM vs GuLF DREAMBoom Deployment,Near Shore DU: 0.15 GDU: 1.46Boom Retrieval,Near Shore DU 7.00 GDU: 20.2611 12. Future Challenges Matching DREAM categories to GuLF questionnaire categories Addressing uncertainty (Monte Carlo approach?) Model calibration Exposure assessor training 12 13. AcknowledgementsWendy McDowell McDowell Safety & HealthServicesHans Kromhout IRAS, UtrechtAnne Sleeuwenhoek - IOM13