The goal of occupational health programmes is to allow workers to maintain their job and their health over several years. The development of effective programmes requires the identification of sectoral, population-based, and workplace-specific risk factors. This information can then be used to develop prevention policies both for groups and individuals.

The Québec Occupational Health and Safety Commission (Commission de la santé et de la sécurité au travail du Québec) has characterized work activities in 30 industrial, commercial, and service sectors (Commission de la santé et de la sécurité au travail 1993). Its surveys reveal that occupational dermatoses are most prevalent in the food and beverage industries, medical and social services, miscellaneous commercial and personal services and construction (including public works). Affected workers are typically engaged in service, manufacturing, assembly, repair, materials handling, food-processing, or health-care activities.

Occupational dermatoses are particularly prevalent in two age groups: young and inexperienced workers who may be unaware of the sometimes insidious risks associated with their work, and those workers approaching retirement age who may not have noticed the progressive drying of their skin over the years, which increases over several consecutive workdays. Because of such dehydration, repeated exposure to previously well-tolerated irritant or astringent substances may cause irritative dermatitis in these workers.

As table 1 indicates, even though most cases of occupational dermatoses do not involve compensation exceeding two weeks, a significant number of cases may persist for over two months (Durocher and Paquette 1985). This table clearly illustrates the importance of preventing chronic dermatoses requiring prolonged work absences.

Table 1. Occupational dermatoses in Quebec in 1989: Distribution by length of compensation

Source: Commission de la santé et de la sécurité au travail, 1993.

Risk Factors

Many substances used in industry are capable of causing dermatoses, the risk of which depends on the concentration of the substance and the frequency and duration of skin contact. The general classification scheme presented in table 2 (overleaf) based on the classification of risk factors as mechanical, physical, chemical or biological, is a useful tool for the identification of risk factors during site visits. During workplace evaluation, the presence of risk factors may be either directly observed or suspected on the basis of observed skin lesions. Particular attention is paid to this in the classification scheme presented in table 2. In some cases effects specific to a given risk factor may be present, while in others, the skin disorders may be associated with several factors in a given category. Disorders of this last type are known as group effects. The specific cutaneous effects of physical factors are listed in table 2 and described in other sections of this chapter.

Table 2. Risk factors and their effects on the skin

Mechanical factors

Trauma
Friction
Pressure
Dusts

Physical factors

Radiation
Humidity
Heat
Cold

Chemical factors

Acids, bases
Detergents, solvents
Metals, resins
Cutting oils
Dyes, tar
Rubber, etc.

Biological factors

Bacteria
Viruses
Dermatophytes
Parasites
Plants
Insects

Risk co-factors

Eczema (atopic, dyshidrotic, seborrhoeic, nummular)
Psoriasis
Xeroderma
Acne

Group effects

Cuts, punctures, blisters
Abrasions, isomorphism
Lichenification
Calluses

Specific effects

Photodermatitis, radiodermatitis, cancer
Maceration, irritation
Heat rash, burns, erythema
Frostbite, xeroderma, urticaria, panniculitis, Raynaud’s phenomenon

Group effects

Dehydration
Inflammation
Necrosis
Allergy
Photodermatitis
Dyschromia

Specific effects

Pyodermatitis
Multiple warts
Dermatomycosis
Parasitosis
Phytodermatitis
Urticaria

Mechanical factors include repeated friction, excessive and prolonged pressure, and the physical action of some industrial dusts, whose effects are a function of the shape and size of the dust particles and the extent of their friction with the skin. The injuries themselves may be mechanical (especially in workers exposed to repeated vibrations), chemical, or thermal, and include physical lesions (ulcers, blisters), secondary infection, and isomorphism (Koebner phenomenon). Chronic changes, such as scars, keloid, dyschromia, and Raynaud’s phenomenon, which is a peripheral neurovascular alteration caused by prolonged use of vibrating tools, may also develop.

Chemical factors are by far the most common cause of occupational dermatoses. To establish an exhaustive list of the many chemicals is not practical. They may cause allergic, irritant or photodermatotic reactions, and may leave dyschromic sequelae. The effects of chemical irritation vary from simple drying to inflammation to complete cell necrosis. More information on this subject is provided in the article on contact dermatitis. Material Safety Data Sheets, which provide toxicological and other information are indispensable tools for developing effective preventive measures against chemicals. Several countries, in fact, require chemical manufacturers to provide every workplace using their products with information on the occupational health hazards posed by their products.

Bacterial, viral and fungal infections contracted in the workplace arise from contact with contaminated materials, animals, or people. Infections include pyodermatitis, folliculitis, panaris, dermatomycosis, anthrax, and brucellosis. Workers in the food-processing sector may develop multiple warts on their hands, but only if they have already suffered microtraumas and are exposed to excessive levels of humidity for prolonged periods (Durocher and Paquette 1985). Both animals and humans such as day-care and health-care workers, may act as vectors for parasitic contamination like mites, scabies and head lice. Phytodermatitis may be caused by plants (Rhus sp.) or flowers (alstromeria, chrysanthemums, tulips). Finally, some wood extracts may cause contact dermatitis.

Risk Co-factors

Some non-occupational cutaneous pathologies may exacerbate the effects of environmental factors on workers’ skin. For example, it has long been recognized that the risk of irritant contact dermatitis is greatly increased in individuals with a medical history of atopy, even in the absence of an atopic dermatitis. In a study of 47 cases of irritant contact dermatitis of the hands of food-processing workers, 64% had a history of atopy (Cronin 1987). Individuals with atopic dermatitis have been shown to develop more severe irritation when exposed to sodium lauryl sulphate, commonly found in soaps (Agner 1991). Predisposition to allergies (Type I) (atopic diathesis) does not however increase the risk of delayed allergic (Type IV) contact dermatitis, even to nickel (Schubert et al. 1987), the allergen most commonly screened for. On the other hand, atopy has recently been shown to favour the development of contact urticaria (Type I allergy) to rubber latex among health-care workers (Turjanmaa 1987; Durocher 1995) and to fish among caterers (Cronin 1987).

In psoriasis, the outmost layer of the skin (stratum corneum) is thickened but not calloused (parakeratotic) and less resistant to skin irritants and mechanical traction. Frequent skin injury may worsen pre-existing psoriasis, and new isomorphic psoriatic lesions may develop on scar tissue.

Repeated contact with detergents, solvents, or astringent dusts may lead to secondary irritant contact dermatitis in individuals suffering from xeroderma. Similarly, exposure to frying oils may exacerbate acne.

Prevention

A thorough understanding of relevant risk factors is a prerequisite to establishing prevention programmes, which may be either institutional or personal ones such as relying on personal protective equipment. The efficacy of prevention programmes depends on the close collaboration of workers and employers during their development. Table 3 provides some information on prevention.

Table 3. Collective measures (group approach) to prevention

Collective measures

• Substitution

• Environmental control:

Use of tools for handling materials
Ventilation
Closed systems
Automation

• Information and training

• Careful work habits

• Follow-up

Personal protection

• Skin hygiene

• Protective agents

• Gloves

Workplace Prevention

The primary goal of workplace preventive measures is the elimination of hazards at their source. When feasible, substitution of a toxic substance by a non-toxic one is the ideal solution. For example, the toxic effects of a solvent being incorrectly used to clean the skin can be eliminated by substituting a synthetic detergent that presents no systemic hazard and that is less irritating. Several non-allergenic cement powders which substitute ferrous sulphate for hexavalent chromium, a well-known allergen, are now available. In water-based cooling systems, chromate-based anti-corrosion agents can be replaced by zinc borate, a weaker allergen (Mathias 1990). Allergenic biocides in cutting oils can be replaced by other preservatives. The use of gloves made of synthetic rubber or PVC can eliminate the development of latex allergies among health-care workers. Replacement of aminoethanolamine by triethanolamine in welding fluxes used to weld aluminium cables has led to a reduction in allergies (Lachapelle et al. 1992).

Modification of production processes to avoid skin contact with hazardous substances may be an acceptable alternative when substitution is impossible or the risk is low. Simple modifications include using screens or flexible tubes to eliminate splashing during the transfer of liquids, or filters that retain residues and reduce the need for manual cleaning. More natural grasp points on tools and equipment that avoid exerting excessive pressure and friction on the hands and that prevent skin contact with irritants may also work. Local capture ventilation with capture inlets that limit nebulisation or reduce the concentration of airborne dusts are useful. Where processes have been completely automated in order to avoid environmental hazards, particular attention should be paid to training workers responsible for repairing and cleaning the equipment and specific preventive measures may be required to limit their exposure (Lachapelle et al. 1992).

All personnel must be aware of the hazards present in their workplace, and collective measures can only be effective when implemented in conjunction with a comprehensive information programme. Material Safety Data Sheets can be used to identify hazardous and potentially hazardous substances. Hazard warning signs can be used to rapidly identify these substances. A simple colour code allows visual coding of the risk level. For example, a red sticker could signal the presence of a hazard and the necessity of avoiding direct skin contact. This code would be appropriate for a corrosive substance that rapidly attacks the skin. Similarly, a yellow sticker could indicate the need for prudence, for example when dealing with a substance capable of damaging the skin following repeated or prolonged contact (Durocher 1984). Periodic display of posters and the occasional use of audio-visual aids reinforce the information delivered and stimulate interest in occupational dermatosis prevention programmes.

Complete information on the hazards associated with work activities should be provided to workers prior to starting work. In several countries, workers are given special occupational training by professional instructors.

Workplace training must be repeated each time a process or task is changed with resulting change in risk factors. Neither an alarmist nor paternalistic attitude favours good working relationships. Employers and workers are partners who both desire work to be executed safely, and the information delivered will only be credible if it is realistic.

Given the absence of safety standards for dermatotoxic substances (Mathias 1990), preventive measures must be supported by vigilant observation of the state of workers’ skin. Fortunately this is easily implemented, since the skin, particularly that on the hands and face, can be directly observed by everyone. The goal of this type of observation is the identification of early signs of cutaneous modifications indicating an overwhelming of the body’s natural equilibrium. Workers and health and safety specialists should therefore be on the lookout for the following early warning signs:

• progressive drying
• maceration
• localized thickening
• frequent trauma
• redness, particularly around hairs.

Prompt identification and treatment of cutaneous pathologies is essential, and their underlying causal factors must be identified, to prevent them from becoming chronic.

When workplace controls are unable to protect the skin from contact with hazardous substances, the duration of skin contact should be minimized. For this purpose, workers should have ready access to appropriate hygienic equipment. Contamination of cleaning agents can be avoided by using closed containers equipped with a pump that dispenses an adequate amount of the cleanser with a single press. Selecting cleansers requires compromising between cleaning power and the potential for irritation. For example, so-called high-performance cleansers often contain solvents or abrasives which increase irritation. The cleanser selected should take into account the specific characteristics of the workplace, since workers will often simply use a solvent if available cleansers are ineffective. Cleansers may take the form of soaps, synthetic detergents, waterless pastes or creams, abrasive preparations and antimicrobial agents (Durocher 1984).

In several occupations, the application of a protective cream before work facilitates skin cleaning, regardless of the cleaner used. In all cases, the skin must be thoroughly rinsed and dried after each washing. Failure to do so may increase irritation, for example by re-emulsification of the soap residues caused by the humidity inside impermeable gloves.

Industrial soaps are usually provided as liquids dispensed by hand pressure. They are composed of fatty acids of animal (lard) or vegetable (oil) origin, buffered with a base (e.g., sodium hydroxide). Buffering may be incomplete and may leave residual free radicals that are capable of irritating the skin. To avoid this, a near-neutral pH (4 to 10) is desirable. These liquid soaps are adequate for many tasks.

Synthetic detergents, available in both liquid and powder form, emulsify greases. Thus they usually remove the human skin’s sebum, which is a substance that protects the skin against drying. Skin emulsification is generally less marked with soaps than with synthetic detergents and is proportional to detergent concentration. Emollients such as glycerine, lanolin, and lecithin are often added to detergents to counteract this effect.

Pastes and creams, also known as “waterless soaps” are emulsions of oil-based substances in water. Their primary cleaning agent is a solvent, generally a petroleum derivative. They are called “waterless” because they are effective in the absence of tap water, and are typically used to remove stubborn soils or to wash hands when water is unavailable. Because of their harshness, they are not considered cleansers of choice. Recently, “waterless soaps” containing synthetic detergents that are less irritating to the skin than solvents have become available. The American Association of Soap and Detergent Manufacturers recommends washing with a mild soap after using solvent-based “waterless soaps.” Workers who use “waterless soaps” three or four times per day should apply a moisturizing lotion or cream at the end of the work day, in order to prevent drying.

Abrasive particles, which are often added to one of the cleaners described above to increase their cleaning power are irritants. They may be soluble (e.g., borax) or insoluble. Insoluble abrasives may be mineral (e.g., pumice), vegetal (e.g., nut shells) or synthethic (e.g., polystyrene).

Antimicrobial cleaners should only be used in workplaces where there is a real risk of infection, since several of them are potential allergens and workers should not be exposed needlessly.

Under the influence of certain substances or repeated washings, workers’ hands may tend to dry out. Long-term maintenance of good skin hygiene under these conditions requires daily moisturizing, the frequency of which will depend on the individual and the type of work. In many cases, moisturizing lotions or creams, also known as hand creams, are adequate. In cases of severe drying or when the hands are immersed for prolonged periods, hydrophilic vaselines are more appropriate. So-called protective or barrier creams are usually moisturizing creams; they may contain silicones or zinc or titanium oxides. Exposure-specific protective creams are rare, with the exception of those which protect against ultraviolet radiation. These have been greatly improved over the last few years and now provide effective protection against both UV-A and UV-B. A minimum protection factor of 15 (North American scale) is recommended. StokogarÔ cream appears to be effective against contact dermatitis caused by poison ivy. Protective or barrier creams should never be seen as equivalent to some form of invisible impermeable glove (Sasseville 1995). Furthermore, protective creams are only effective on healthy skin.

While few people like wearing protective equipment, there may be no choice when the measures described above are inadequate. Protective equipment includes: boots, aprons, visors, sleeves, overalls, shoes, and gloves. These are discussed elsewhere in the Encyclopaedia.

Many workers complain that protective gloves reduce their dexterity, but their use is nevertheless inevitable in some situations. Special efforts are required to minimize their inconvenience. Many types are available, both permeable (cotton, leather, metal mesh, KevlaÔasbestos) and impermeable (rubber latex, neoprene, nitrile, polyvinyl chloride, VitoÔ, polyvinyl alcohol, polyethylene) to water. The type selected should take into account the specific needs of each situation. Cotton offers minimal protection but good ventilation. Leather is effective against friction, pressure, traction, and some types of injury. Metal mesh protects against cuts. KevlaÔis fire-resistant. Asbestos is fire- and heat-resistant. The solvent resistance of water-impermeable gloves is highly variable and depends on their composition and thickness. To increase solvent resistance, some researchers have developed gloves incorporating multiple polymer layers.

Several characteristics have to be taken into account when selecting gloves. These include thickness, flexibility, length, roughness, wrist and finger adjustment, and chemical, mechanical, and thermal resistance. Several laboratories have developed techniques, based on the measurement of break-through times and permeability constants, with which to estimate the resistance of gloves to specific chemicals. Lists to help guide glove selection are also available (Lachapelle et al. 1992; Berardinelli 1988).

In some cases, the prolonged wear of protective gloves may cause allergic contact dermatitis due to glove components or to allergens that penetrate the gloves. Wearing protective gloves is also associated with an increased risk of skin irritation, due to prolonged exposure to high levels of humidity within the glove or penetration of irritants through perforations. To avoid deterioration of their condition, all workers suffering from hand dermatitis, regardless of its origin, should avoid wearing gloves that increase the heat and humidity around their lesions.

Establishing a comprehensive occupational dermatosis prevention programme depends on careful adaptation of standards and principles to the unique characteristics of each workplace. To ensure their effectiveness, prevention programmes should be revised periodically to take into account changes in the workplace, experience with the programme and technological advances.

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