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

Why is dermal exposure assessment important?

John Cherrie

Summary…

• The skin

• Effects of chemicals on the skin

• Uptake through the skin

• How should we deal with dermal exposure

The skin…

• Two-way protective barrier

• Complex structure that is metabolically active

• About 2m2 area for an adult

• Hands comprise about 5% and arms 15% of area

Why is the skin important?

• Controls the loss of moisture

• Protect against injury

• Provides a protective barrier against harmful substances

• Reduces the harmful effects of UV radiation

• Acts as a sensory organ - touch, temperature

• Helps regulate body temperature

• Helps detect and protect against infections

• Produces vitamin D

Structure of the skin…

Contact dermatitis…

Key signs of dermatitis…

• Redness

• Scaling/flaking

• Blistering

• Weeping

• Cracking

• Swelling

• Itching

What causes occupational dermatoses…

• Chemical

• Irritants and allergens

• Mechanical

• Friction and pressure

• Physical

• Heat, cold, radiation

• Biological

• Infection of previous lesions

Incidence (UK)…

http://research.bmh.manchester.ac.uk/epidemiology/COEH/research/thor/schemes/epiderm/

Occupations with the highest dermatitis incidence (UK)...

• Florists (109 cases per 100,000 workers per year),

• Hairdressers and barbers (81 cases per 100,000 workers per yr),

• Beauticians (73 cases per 100,000 workers per yr),

• Cooks (61 cases per 100,000 workers per yr)

• Metal working machine operatives (54 cases per 100,000 workers per yr).

Industries with the highest incidence (UK)…

Industry Per

100,000

Personal service activities 53

Human health activities 17

Manufacture of chemicals 19

Extraction crude petroleum and gas 18

Manufacture base metals 14

Financial and insurance activities 0.4/100,000

Cumulative concept of dermatitic damage…

Time

Threshold

after Malten/van der Walle

Dermatitis

Allergic dermatitis (type I)…

Allergic dermatitis (type IV)…

Systemic effects…

• Some chemicals can pass through the unbroken skin and contribute to total body burden

• Skin notation

• Solvents, pesticides, some nanomaterials

• Inhalation limits- but no dermal workplace exposure limits…

• Approximately 275 compounds are considered to be skin hazards

• 92% show a theoretical potential for dermal absorption or toxicity, only 35% have a skin notation

Chemicals that pass through the skin…

• Lipophillicsubstances

• Solvents

• Pesticides

• Biocides

• Mercury

• PCBs

• PAHs

• Isocyanates

How absorption/uptake takes place…

VIABLE EPIDERMIS

BLOOD

LOWER DERMIS / SUBCUTANEOUS FAT

(1) (2)(3)

Hair follicle

CHEMICAL

DEPOSIT

Corneocytes

Lipid

matrix

ST

RA

TU

M C

OR

NE

UM

1. Extracellular

diffusion- lipophilic

chemicals

2. Intracellular diffusion

–hydrophilic

chemicals

3. Transapendageal

transport (via

hairs/sebaceous

glands) – large

molecules

What factors influence uptake

Workplaces where dermal exposure is important

• Petrochemicals

• Painters

• Dry cleaners

• Farmers

• Crop-harvesters

• Shoe manufacturers

• Engineers

• Hairdressers, nurses and many, many more…

Most common agents for dermatitis

Occupational hygiene and dermal exposure…

• The same framework as used in inhalation exposure scenarios

Recognition

Evaluation

Control

How do we know if dermal exposure is an issue?- Recognition

• Skin notation

• Risk phrases

• All wet work

Evaluation…

• Who is exposed?

• How much are they exposed to?

• How often are they exposed?

• What are existing control measures?

• Are they adequate to control risk?

Control…

• Hierarchy of control

• Elimination

• Substitution

• Engineering controls

• Local controls

• Management/behavioural changes

• PPE

• Health surveillance

• Inspecting for early signs of skin damage

• Skin care programs

Summary…

• Dermal exposure is common across many industrial tasks

• Local effects

• Dermatitis is a big issue!

• Avoidance is better than trying to treat symptoms

• Systemic effects

• Can add to total body burden

• Dermal exposure can be tackled in the same way as inhalation exposure

• Recognition – Evaluation – Control