6. Modelling dermal exposure


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The sixth lecture on modelling exposure for a course held in Norway 2011

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  • Because all of these methods produce estimates of exposure in terms of mass per unit area its often assumed they are interchangeable. They are not! Interception methods measure… >> Do the experiment
  • 50% within +- 100% of average
  • 6. Modelling dermal exposure

    1. 1. Modelling dermal exposure John Cherrie
    2. 2. Outline of the talk… <ul><li>Dermal exposure – it’s not like inhalation exposure </li></ul><ul><li>Modelling dermal exposure: </li></ul><ul><ul><li>Tier 1 tools (TRA, MEASE, RISKOFDERM…) </li></ul></ul><ul><li>Dermal ART – just a DREAM? </li></ul><ul><li>Heavy fuel oil – an example illustrating where we are going </li></ul>
    3. 3. Schneider and colleagues… Schneider et al. Conceptual model for assessment of dermal exposure. Occup Environ Med (1999) vol. 56 (11) pp. 765-73 Surface contamination layer Air compartment Clothing outer layer Skin contamination layer Source Clothing inner layer
    4. 4. Measurement of dermal exposure… <ul><li>What do they measure? </li></ul><ul><li>Interception </li></ul><ul><ul><li>The mass of chemical that lands on the skin over the sampling time (integrated flux) </li></ul></ul><ul><li>Removal </li></ul><ul><ul><li>The mass of contaminant left on the skin </li></ul></ul><ul><li>Fluorescent tracers </li></ul><ul><ul><li>The mass of a surrogate compound retained on the skin </li></ul></ul>
    5. 5. Interception sampling…
    6. 6. Removal sampling…
    7. 7. Fluorescent tracers…
    8. 8. DREAM… van Wendel de Joode et al. DREAM: A method for semi-quantitative dermal exposure assessment. Annals of Occupational Hygiene (2003) vol. 47 (1) pp. 71-87 Emission Deposition Transfer Clothing Body surface factor
    9. 9. DREAM… <ul><li>Complex deterministic algorithm </li></ul><ul><li>Estimates are reasonably reproducible between assessors </li></ul><ul><li>Only provides estimates in “Dream Units” - DU </li></ul>van Wendel de Joode et al. Accuracy of a semiquantitative method for Dermal Exposure Assessment (DREAM). Occup Environ Med (2005) vol. 62 (9) pp. 623-32
    10. 10. Heavy fuel oil (HFO)… <ul><li>Industrial fuel for power stations </li></ul><ul><li>Heating large industrial sites </li></ul><ul><li>Heating fuel in hospitals and distilleries in remote area (e.g. Scottish Highlands) </li></ul><ul><li>Marine oil </li></ul>
    11. 11. What is HFO? <ul><li>Heavy fuel oil (HFO): blended hydrocarbon residues from refinery distillation and cracking processes </li></ul><ul><li>High MW compounds: aromatic, aliphatic and naphthenic hydrocarbons, along with asphaltenes and some heterocyclic compounds containing sulphur, nitrogen and oxygen </li></ul><ul><li>UK crude is predominantly from the North Sea A barrel of North Sea crude oil will usually yield about 12% of HFO </li></ul>
    12. 12. What are the health concerns? <ul><li>Prolonged repeated contact with the skin may cause: </li></ul><ul><ul><li>oil acne </li></ul></ul><ul><ul><li>oil folliculitis </li></ul></ul><ul><ul><li>dermatitis. </li></ul></ul><ul><li>HFOs contains compounds that may cause skin cancer, including benzo(a)pyrene and other polycyclic aromatic hydrocarbons (PAHs) </li></ul>
    13. 13. Composition…
    14. 14. Aims of our study… <ul><li>To develop a validated method for measuring dermal HFO exposure </li></ul><ul><li>To collect exposure data using the validated method </li></ul><ul><li>To collect contextual exposure information and use these data to apply the DREAM model </li></ul>
    15. 15. Methods… <ul><li>Quantitative data collection </li></ul><ul><ul><li>Validated method developed at IOM </li></ul></ul><ul><li>Semi-quantitative data collection </li></ul><ul><ul><li>Using modified DREAM (van Wendel de Joode et al, 2003) (deposition route removed) </li></ul></ul><ul><ul><ul><li>By proxy (questionnaires sent to company contact) </li></ul></ul></ul><ul><ul><ul><li>Direct assessment at sites </li></ul></ul></ul><ul><li>Comparison of measured vs semi-quantitative </li></ul>
    16. 16. Methods… <ul><li>Removal method using clinical wipes saturated with 70% isopropyl alcohol – three sequential wipes </li></ul><ul><ul><li>25 cm 2 forearm and neck </li></ul></ul><ul><ul><li>Palms of each hand </li></ul></ul><ul><li>Collected following the completion of task and before rest breaks </li></ul><ul><li>Some pre-task samples also collected </li></ul><ul><li>Filed blanks </li></ul><ul><li>GG-MS analysis for marker PAHs </li></ul>
    17. 17. Sites investigated… <ul><li>Production </li></ul><ul><ul><li>2 oil refineries </li></ul></ul><ul><li>Distribution </li></ul><ul><ul><li>2 fuel distribution terminals </li></ul></ul><ul><ul><ul><li>including 1 associated with distribution by shipping </li></ul></ul></ul><ul><li>Use </li></ul><ul><ul><li>2 Energy providers </li></ul></ul><ul><ul><li>1 Power plant engine building and repair </li></ul></ul>
    18. 18. Dermal exposure by type of site…
    19. 19. DREAM vs measurements…
    20. 20. Task average data… van Wendel de Joode et al. Accuracy of a semiquantitative method for Dermal Exposure Assessment (DREAM). Occup Environ Med (2005) vol. 62 (9) pp. 623-32
    21. 21. The way forward? <ul><li>The Advanced REACH Tool </li></ul><ul><ul><li>www.AdvancedREACHtool.com </li></ul></ul><ul><li>Currently for inhalation exposure only </li></ul><ul><li>Uses Bayesian algorithm to combine model prediction with measurements </li></ul><ul><ul><li>Model estimates of the mean exposure level and the uncertainty around this </li></ul></ul><ul><ul><li>Updated with whatever measurements are available </li></ul></ul>
    22. 22. Where do we want to go next? <ul><li>Develop a Dermal ART </li></ul><ul><ul><li>Plans to use DREAM to develop the dermal tool </li></ul></ul><ul><ul><li>We have started preparatory work this year </li></ul></ul><ul><ul><li>Exploring ways of combining different measurement approaches , e.g. removal or interception, to give a single estimate </li></ul></ul><ul><li>Hope to extend measurement data and validation of DREAM to other oils and fuels, e.g. gasoline and lubricating oil </li></ul>