Dermal Exposures

Anatomy of the Skin

• Cutaneous Membrane

• Largest organ of body (2500-3000 in2 in most adults)

• Varying thickness (0.5 - 4 mm)

• Diverse functions:– Protection, excretion, sensation– Maintenance of fluid, electrolytes, temperature

Epidermis

• Outermost layer of skin

• Cells migrate outward through this layer, in the process dying and becoming converted to the water-repellent protein keratin.

• Inner (living) portion produces pigment (melanin) genetically driven to provide protection against electromagnetic radiation

• Inner portion also produces new cells (mitosis)

Dermis

• Inner layer of skin• Parallel ridges give rise to fingerprints• Provides structural integrity• Capillary blood supply provides “plumbing”

to support the movement of materials in the skin

• Blood vessels also act to permit temperature regulation through the skin

Pores and Hair Follicles

• About 0.1% of skin surface area

• Sebaceous glands secrete oil for the hair (prevents excess moisture movement)

• Sweat glands (3000/in2 on the palms!) provide water to the skin’s surface to facilitate cooling through evaporation (and increased loss of keratin layer)

• Hair follicles tunnel into dermis

Contact Dermatitis

• Localized effect in response to chemical

• Keratin layer is a barrier, except to corrosives and if physically compromised

• Irritation results from inflammation and swelling, with sensory response

• Cell death and damage to blood vessels can result

Irritant Contact Dermatitis

• Chemical damage– Protected by oils and dead cells

• Physical damage– Fibers, particulates can penetrate and abrade

skin

• Removal of oils and damage to keratin layer– Solvents– Soaps and detergents

Allergic Contact Dermatitis

• Wide variation in response between workers

• Sensitization permits increase in response with repeated contact

• Results from immune system response to “invasion” of chemical-protein complexes produced when the chemical is absorbed into the skin

Photodermatitis

• Results from photo-stimulated reaction of chemicals on the skin

Hair Problems

• Hair loss– Death of cells at hair root– Chemical or radiation exposure

• Color change– Most often caused by metals such as copper and

cobalt– Has absolutely nothing to do with age

Acne

• Result from blocked hair follicles trapping oils produced by the sebaceous glands

• Can be exacerbated by temperature, chemical exposure, or physical stressors

• Chloracne is similar but blockage results from damaged keratin rather than oil

Alteration of Skin Pigmentation

• Phenolic compounds can interfere with melanin production

• More severe cell damage can result in healing without regeneration of melanin producing cells

Corrosives

• Produce acute and general tissue damage

• Acids– “Strong” acids dissociate completely– Sometimes acid precursors react with water

from or on skin

• Bases– Strong bases (e.g. sodium hydroxide) equally

damaging, and harder to remove

Cancer

• UV light implicated in many skin cancers

• “Tar warts” (some eventually becoming malignant) associated with polycyclic hydrocarbons

• Similar evidence associated with chronic exposure to arsenic

Anatomy of the Eye

Eye Hazards

• Chemical Hazards– Corrosive vapors and splashes causing direct

damage to eye is most important– Eye provides only a minor route of general systemic

chemical exposure

• Physical Hazards– Cuts and abrasions due to flying particles– Irritation due to particulate pollution– Optical damage (e.g. lasers)

Prevention of Irritation or Damage

• Engineering Controls– Task re-design– Fume hoods, glove boxes, robots– Splash guards, enclosed pumps

• Administrative Controls– Allergy screening prior to work assignment and

monitoring for possible reassignment– On-going training regarding materials handling

procedures

Prevention of Irritation or Damage (cont’d)

• Personal Protective Equipment– Barrier creams– Protective clothing– Gloves– Safety glasses– Face shields