the conceptual model of dermal exposure

WORKING FOR A HEALTHY FUTURE

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

A conceptual model of dermal exposure

John Cherrie

…acknowledging the contribution of Schneider, Vermeulen, Brouwer, Kromhout and Fogh

Summary...

• Why do we need a conceptual model of dermal exposure?

• From source to exposure: the compartments• The mass transport processes• Uptake• Some implications for measurement

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Why do we need a model?

• Present methods for dermal exposure monitoring are:• pragmatic• non-standard

• Contextual information generally not collected

• Relevance of other measurements not clear

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What is the model?

Surface contamination layer Air compartment

Clothing outer layer

Skin contamination layer

Source

Clothing inner layer

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Environmental compartments…

Surface contamination layer Air compartment

Source

Personal Barrier

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Personal compartments…

Clothing outer layer

Skin contamination layer

Clothing inner layer

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Personal Barrier

Stratum Corneum Barrier

Clothing Barrier

Emission processes...

Source

Personal Barrier

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Deposition and Losses

Surface contamination layer Air compartment

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Transfer...

Surface contamination layer

Clothing outer layer

Skin contamination layer

Clothing inner layer

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Penetration and Permeation...

Clothing outer layer

Clothing inner layer

Clothing Barrier

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Redistribution...

Surface contamination layer Air compartment

Clothing outer layer

Skin contamination layer

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Personal Barrier

Stratum Corneum Barrier

Uptake...

Uptake by diffusion… concentration, area exposed, mass and duration are important

Skin contamination layer

Stratum Corneum Barrier

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Measurement implications...

• Measurement of compartment mass and mass transfer are different

• Mass transfer should be measured under standard conditions

• Particles are less likely to be taken up than liquids

• We should measure both the mass on skin and uptake

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