My keynote presentation at the Inaugural UK & Ireland Exposure Science meeting, held in Edinburgh during March 2013.

1. WORKING FOR A HEALTHY FUTURE
Estimating Dermal Exposure to
Chemicals
John Cherrie
INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

2. Outline…
• Consider what we mean by dermal
exposure
• How do chemicals enter the body?
• Available measurement methods
• Modelling exposure
• DREAM
• Efforts to improve models
• The GuLF study
• DART
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3. Growing interest in dermal exposure…
Publications in
Scopus by year
2

4. Exposure…
• Ideally, we would like to know there is an
exposure-response relationship
• For inhalation exposure
• Concentration x Duration (mg/m3.hr)
• Uptake
• Cumulative exposure x Breathing rate (mg)
• What should we use for dermal exposure?
3

5. Dermal uptake…
J = kpdC
- where kp is the permeability
constant
Important factors:
• Concentration of contaminant
• Mass on skin
• Area exposed
From Wikipedia.com
• Duration of exposure
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6. How can we measure?
• Interception (e.g. patches)
• The mass of chemical that lands on the skin over the sampling
time (integrated flux)
• Removal (e.g. wipe/wash)
• The mass of contaminant left on the skin
• In-situ (e.g. fluorescence)
• The mass (area) of a surrogate compound retained on the skin
• Tape stripping
• The mass of contaminant in the upper layers of the
stratum corneum
• Biological monitoring
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7. Dermal exposure to metals…
EASE
CaCO3 Zn Pb Sb Ni
Source: http://www.herag.net / 6

8. European and International Standards
• CEN/TC 137 - Assessment of workplace exposure
to chemical and biological agents
• Workplace exposure - Strategy for the evaluation of
dermal exposure (CEN/TR 15278:2006)
• Workplace exposure - Measurement of dermal exposure
- Principles and methods (CEN/TS 15279:2006)
• ISO TC146 SC2 WG8 - Assessment of
contamination of skin and surfaces from airborne
chemicals
• TR 14294 – accepted 3rd May 2011
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9. Biologically-relevant samplers…
• An interception sampler that mimics the skin
• with a diffusion membrane, ideally chosen with similar uptake
characteristics to the skin
• adsorbent material
• impervious backing
• Prototype IOM dermal
sampler
• NIOSH POD
• 5-layer Passive
Organic Dermal
sampler
Lindsay FE, Semple S, Robertson A, Cherrie JW. (2006) Development of a
biologically relevant dermal sampler. Annals of Occupational 8
Hygiene;50(1):85-94.

10. Problems with the IOM sampler…
• A range of membranes tested but none
completely suitable
• All more permeable than skin
• Adsorbent more easily saturated than we
would have wished
• Need to correct for air concentration
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11. Schneider et al conceptual model
Surface contamination
layer Air compartment
Source
Clothing outer layer
Clothing inner layer
Skin contamination layer
Schneider et al. (1999) Conceptual model for assessment of dermal
exposure. Occup Environ Med vol. 56 (11) pp. 765-73. 10

12. Vermeulen et al (2000)
• Identified the exposure pathways in rubber
manufacturing
• They measured…
• Air concentration – both near and far-field
• Dermal loading
• They showed that…
• Hand (wrist) contamination was on average highest
• Strong correlation between hand (wrist) and whole
body contamination
Vermeulen R, Heideman J, Bos RP, Kromhout H. (2000) Identification of dermal
exposure pathways in the rubber manufacturing industry. Ann Occup 11
Hyg.;44(7):533-541.

13. Different process – different pathways
Curing Pre-treatment
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14. DREAM…
• Based on Schneider et al model
• Estimates from descriptive task information
• Assessments are reproducible between
assessors
• Estimates exposure in
“Dream Units” - DU
• Validation study showed
reasonable correlation with
measurement data
van Wendel de Joode et al. (2005) Occup Environ; 62(9): 623-32.
van Wendel de Joode et al. (2005) J Expo Anal Environ Epidemiol; 15(1): 111- 13
120.

15. The GuLF Study…
• A large epidemiological study to investigate
potential health risks for clean-up workers involved
with the Deepwater Horizon oil spill
• Using an updated version of DREAM for dermal
exposure assessment
• Need to assess exposure to
• Residues, (e.g. VOCs, PAHs, BTEX)
• Dispersants (e.g. 2-butoxyethanol,
propylene glycol)
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16. DREAM
Exposure Assessors estimate exposure from each of
the three pathways of dermal exposure:
• Emission
• Surface Contact
• Deposition
Number of Skin area Substance
exposure events exposed characteristics
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17. Personal protective equipment…
• Studies of exposure often show a high degree of
protection.
• Creely & Cherrie found >99% reduction in contaminant inside
gloves
• Available biomonitoring studies suggest gloves are
less effective
• Scheepers and colleagues found…
• With polyethylene gloves median reduction of 51% excretion
of 1-hydroxypyrene in urine
• Vinyl gloves and Tyvek sleeves showed a 97% reduction in
skin contamination with pyrene and benzo(a)pyrene and a
lowering in urinary excretion of 1-hydroxypyrene by 57%
Creely KS, Cherrie JW. Ann OccupHyg 2001;45:137–43.
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Scheeperset al.Scan J Work, Environ Health 2009;35:212–221.

18. Asphalt exposure…
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19. Adaption of DREAM for PPE…
• We argue that the biomonitoring data are more
reliable indicators of protection
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20. DART…
• Dermal Advanced Dermal exposure
database
REACH Tool from
DART deterministic
the ART Consortium model
Similarity module to
• Combine mechanistic select data
model (DREAM?)
Bayesian process
and to combine data
and model output
• Exposure data
using
• A Bayesian process Exposure estimates
for risk assessment
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21. News…
• The WHO IPCS will publish
an Environmental Health
Criteria Monograph (EHC) on
Dermal Exposurelater this
year.
• This is a companion to the
earlier volume on Dermal
Absorption, published 2006.
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22. Questions and thanks…
My collaborators…
Melanie Gorman Ng1, Mark Stenzel2, Richard Kwok3,
Berna van Wendel de Joode4,
Patricia Stewart5
1 IOM, Centre for Human Exposure
Science
2 Exposure Assessment The work was partly funded by…
Applications, LLC
3 National Institute of Environmental
Health Sciences
4 Universidad Nacional de Costa
Rica
5 Stewart Exposure Assessments,
LLC
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