6. Modelling dermal exposure

WORKING FOR A HEALTHY FUTURE

INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

Modelling dermal exposure

John Cherrie

Outline of the talk…

• Dermal exposure – it’s not like inhalation exposure

• Modelling dermal exposure:• Tier 1 tools (TRA, MEASE, RISKOFDERM…)

• Dermal ART – just a DREAM?• Heavy fuel oil – an example illustrating where we

are going

Schneider and colleagues…

Surface contamination layer Air compartment

Clothing outer layer

Skin contamination layer

Source

Clothing inner layer

Schneider et al. Conceptual model for assessment of dermal exposure. Occup Environ Med (1999) vol. 56 (11) pp. 765-73

Measurement of dermal exposure…

• What do they measure?• Interception• The mass of chemical that lands on the skin over

the sampling time (integrated flux)

• Removal• The mass of contaminant left on the skin

• Fluorescent tracers • The mass of a surrogate compound retained on

the skin

Interception sampling…

Removal sampling…

Fluorescent tracers…

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

DREAM…

• Complex deterministic algorithm

• Estimates are reasonably reproducible between assessors

• Only provides estimates in “Dream Units” - DU

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

Heavy fuel oil (HFO)…

• Industrial fuel for power stations• Heating large industrial sites• Heating fuel in hospitals and distilleries in remote

area (e.g. Scottish Highlands)• Marine oil

What is HFO?

• Heavy fuel oil (HFO): blended hydrocarbon residues from refinery distillation and cracking processes

• High MW compounds: aromatic, aliphatic and naphthenic hydrocarbons, along with asphaltenes and some heterocyclic compounds containing sulphur, nitrogen and oxygen

• UK crude is predominantly from the North Sea A barrel of North Sea crude oil will usually yield about 12% of HFO

What are the health concerns?

• Prolonged repeated contact with the skin may cause:• oil acne • oil folliculitis • dermatitis.

• HFOs contains compounds that may cause skin cancer, including benzo(a)pyrene and other polycyclic aromatic hydrocarbons (PAHs)

Composition…

Aims of our study…

• To develop a validated method for measuring dermal HFO exposure

• To collect exposure data using the validated method

• To collect contextual exposure information and use these data to apply the DREAM model

Methods…

• Quantitative data collection• Validated method developed at IOM

• Semi-quantitative data collection• Using modified DREAM (van Wendel de Joode

et al, 2003) (deposition route removed)• By proxy (questionnaires sent to company

contact)• Direct assessment at sites

• Comparison of measured vs semi-quantitative

Methods…

• Removal method using clinical wipes saturated with 70% isopropyl alcohol – three sequential wipes• 25 cm2 forearm and neck• Palms of each hand

• Collected following the completion of task and before rest breaks

• Some pre-task samples also collected• Filed blanks• GG-MS analysis for marker PAHs

Sites investigated…

• Production• 2 oil refineries

• Distribution• 2 fuel distribution terminals

• including 1 associated with distribution by shipping

• Use• 2 Energy providers• 1 Power plant engine building and repair

Dermal exposure by type of site…

DREAM vs measurements…

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

The way forward?

• The Advanced REACH Tool • www.AdvancedREACHtool.com

• Currently for inhalation exposure only• Uses Bayesian algorithm to combine model

prediction with measurements• Model estimates of the mean exposure level and

the uncertainty around this• Updated with whatever measurements are

available

Where do we want to go next?

• Develop a Dermal ART• Plans to use DREAM to develop the dermal tool• We have started preparatory work this year• Exploring ways of combining different measurement

approaches , e.g. removal or interception, to give a single estimate

• Hope to extend measurement data and validation of DREAM to other oils and fuels, e.g. gasoline and lubricating oil