The final lecture slides for a CES at the Australian Institute of Occupational Hygienists conference 2017 in Canberra.

1. INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org
Interpretation of dermal
exposure measurements
& model outputs
John Cherrie

2. Summary…
• Methodological and quality
issues
• Contextual information
• Data analysis, what do the
results mean?

3. What do we assess?
• Interception measurements assess
cumulative amount of contaminant on skin
• In many cases they are unrealistic
• Removal samples recover what’s left
• They are more realistic but may underestimate
because of losses
• Fluorescent monitoring is useful for
assessing the area exposed
• May overestimate mass for reasons similar to
interception sampling
• Biological monitoring integrates all routes
• It is difficult to interpret for this reason

4. Models…
• Dermal exposure models are generally poor
at estimating exposure
• Generally overestimate exposure
• May be best for screening
• Multiple independent assessments reduces
variability
• DREAM / Gulf DREAM are useful for
assessing possible impacts of controls
• Conceptual model can help understanding

5. Measurements…
• No real standardisation of methods
• Quality assurance procedures are
necessary, e.g. assessment of
recovery efficiency
• Interception samplers will give
results that may be an order of
magnitude higher than recovery
samples
• Preliminary data from Gorman-Ng et al
Ng, M. G., de Poot, S., Schmid, K., Cowie, H., Semple, S., & Van Tongeren, M. (2014). A preliminary
comparison of three dermal exposure sampling methods: rinses, wipes and cotton gloves. Environmental
Science: Processes & Impacts, 16(1), 141–147.

6. Wipe vs rinse for particles…
Calcium acetate = CA Epsom salts = ES Zinc oxide = ZO

7. Golve vs Wipe for liquids…

8. Contextual data…
• Contextual data are necessary to properly
interpret measurements or modelled
exposure
• The conceptual model from Schenider et al
helps guide what data should be collected
• Use of the model to map out the exposure
pathways can be helpful
• Linking to air concentrations and surface
samples can further help quantify pathways
• Plan measurement survey using the
conceptual model

9. Interpretation of risks…
• We do not generally have a dermal OEL
• Main exception are REACH dermal
DNELs
• We can generate a pseudo OEL for skin
exposure from the inhalation OEL, e.g.
assuming a certain inhaled air volume
for the working day
• If OEL is 10 mg/m3 and the worker inhales
10 m3 in the working day then then she will
inhale 100 mg of the contaminant

10. An example…
• 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

11. 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)
11

12. Composition…

13. 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

14. 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
14

15. 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
15

16. Dermal exposure by activity…
Hands

17. Dermal exposure by activity…
Forearms

18. How do we interpret these data?
• Exposure levels much lower than
predicted by ECETOC TRA
• Assuming the area of hands and arms is
3700 cm2
• Maximum mass of HFO on skin is then
around 37 mg
• For comparison workers machining
metal typically were exposed to 1400 –
1600 mg MWF on hands

19. DNEL
• Target organ and developmental effects are
associated with the types and levels of
aromatic constituents
• 8hr dermal DNEL for HFO 0.065 mg/kg,
which for a 70kg man would be 4.5 mg
• Maximum exposure 37 mg HFO
• Flux estimated for naphthalene as 0.45 x
10-3 mg/cm2/hr
• 1.6 mg naphthalene could be taken up in
1hr
Jakasa, I., Kezic, S., & Boogaard, P. J. (2015). Dermal uptake of petroleum substances.
Toxicology Letters, 1–17.

20. Summary…
• Interpretation of dermal exposure
measurements is not straightforward
• There is no standardisation and generally
no limit values to compare with
• You need to be a bit creative to come to
some appropriate conclusions