Page 351 - Industrial Ventilation Design Guidebook

5.3 TOXICITY AND RISKS INDUCED BY OCCUPATIONAL EXPOSURE TO CHEMICAL COMPOUNDS 307

glands, phagocytic cells, skin metabolism, and melanin pigmentation (which
protects the skin from ultraviolet irradiation from the sun) belong to the bat-
tery of the dermal defense systems. However, skin is exposed to many chemi-
cal compounds. Skin diseases account for a considerable percentage of all
occupational diseases (20% in Finland). Among exposure-induced skin dis-
eases, inflammations due to both irritation and sensitization are common.
Assessment of skin exposure continues to be relatively difficult because it
is difficult to measure or estimate the dose actually absorbed by the skin,
Toxic Reactions of the Skin Irritation is the most common reaction of
the skin. Skin irritation is usually a local inflammatory reaction. The most
common skin irritants are solvents; dehydrating, oxidizing, or reducing com-
pounds; and cosmetic compounds. 160 Acids and alkalies are common irritants.
Irritation reactions can be divided into acute irritation and corrosion. Necrosis
of the surface of the skin is typical for corrosion. Acids and alkalies also cause
chemical burns. Phenols, organotin compounds, hydrogen fluoride, and yel-
low phosphorus may cause serious burns. 161 Phenol also causes local anesthe-
sia, in fact it has been used as a local anesthetic in minor ear operations such
as puncture of the tyrnpanous membrane in cases of otitis. 36
The common skin reaction allergic contact dermatitis is evoked subsequent
to exposure to a chemical compound via a cell-mediated type IV allergic reac-
tion. Allergic contact dermatitis is also a common skin disease in the occupa-
tional environment. The reaction is compound-specific and re-exposure to very
small amounts of chemical compounds provoke a severe reaction. Skin aller-
gens often have small molecular size and are frequently haptens that become
bound to a protein and in that way induce an immunological reaction. Many
chemical compounds can induce allergic contact dermatitis (see Table 5.18). 161
Especially important inducers of allergic contact dermatitis are metals (nickel)
and metallic compounds (cobalt, chromium, and nickel salts as well as organic
mercurial compounds). Also several cosmetic products, resins, a number of col-
ors, rubber (latex) and leather additives, and pesticides (fungicides such as thi-
urams and dithiocarbamates) are skin allergens. Compounds that belong to the
same group of chemical compounds may cross-sensitize sensitive individuals.
Thiurams and dithiocarbamates are good examples of this: if you are sensitive
to one compound in this group you are allergic to all members of this group of
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chemicals. 162 163 Table 5.19 lists common cross-reacting chemicals. 161
Light and Toxic Reactions In many individuals, exposure to ultraviolet
radiation from the sun causes skin reactions such as erythema, thickening of
the epidermis, and darkening of existing pigment. Exposure to ultraviolet light
also increases the risk of different forms of skin cancers, especially malignant
161
melanoma.
Chemical Acne Many chemical compounds induce skin lesions that are
similar to acne. Oils, tar, creosote, and several cosmetic products induce chemical
acne. These compounds induce keratinization of the sebaceous glands of the skin,
obstruction of the glands, and formation of acne. Chloracne is a specific skin lesion
that is induced by chemical compounds that are structurally similar to 2,3,7,8-tet-
rachloro dibenzo-p-dioxin (TCDD). Chloracne is slow to heal and difficult to