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THE WORK ENVIRONMENT AND THE SKIN
D Koh, C L Goh

INTRODUCTION

The effects of the work environment on the skin are rarely life threatening. However, they can cause much morbidity and suffering to the workers, and are a significant cause of decreased productivity and sickness absence in industry(1).

Occupational dermatoses are defined as any pathological conditions of the skin for which job exposure can be shown to be a major direct or contributory factor(2)

EPIDEMIOLOGY OF OCCUPATIONAL DERMATOSES

In a reported series of 1,727 cases of occupational dermatoses which were confirmed by the Ministry of Labour in Singapore between 1983 to 1987, contact dermatitis was the most common presentation of occupational dermatose3. It accounted for 86% of all cases. About one fifth of the cases were from the construction industry, while the rapidly expanding electronics industry contributed to 15% of all cases. Many of these cases were assessed in a government skin hospital.

A published series of 557 patients with occupational dermatoses seen at a Singapore government skin hospital between 1984 and 1985 reported that the majority of cases were contact dermatiti4. Irritant contact dermatitis was the most predominant (56%) followed by allergic contact dermatitis (39%). A small proportion (5%) of the cases were non-contact dermatitis, such as fibre glass dermatoses, miliaria and oil folliculitis. Most of the affected workers were from the construction (30%), metal and engineering (21%), electrical and electronic (16%), transport (6%) and food catering (4%) industries. Cutting fluids, oil, cement, solvents, detergents and soldering flux were the commonest occupational irritants. The common occupational allergens included chromates, rubber chemicals, resins, nickel and cobalt. A few workers had contact urticana to proteinaceous foods.

It should be remembered that most statistics from notification of occupational diseases are an underestimation of the true magnitude of the problem. Most of the cases reported also required tertiary assessment and management. The types of cases seen at the primary health care level would be different.

Cross-sectional prevalence surveys provide a better reflection of the situation at the industry level. Some prevalence studies have been undertaken in different industries in Singapore (Table 1). point and period prevalence rates. The prevalence I However, the reported rates in all the studies were rates would differ for different industries, and also, not strictly comparable, as they vary between for different countries.

CLINICAL PRESENTATION OF OCCUPATIONAL DERMATOSES

The commonest presentation of occupational dermatosis is contact dermatitis. It accounts for over 90% of all cases seen at the secondary and tertiary levels of care, and a large proportion of the cases seen at the primary care level. Occupational dermatoses can also present in other forms, such as contact urticaria, disorders of pigmentation and skin cancers, although less commonly.

Dermatitis

Dermatitis or eczema (synonymously), is an inflammation of the skin with characteristic morphology but varied cause. Dermatitis is characterized by redness, swelling, small fluid filled blisters, and oozing in the acute state and as a scaly lichenified, thickened, fissured with pigmentary changes in the chronic stage.

Contact dermatitis refers to dermatitis caused by skin contact with an environmental agent. Most occupational dermatoses are eczematous reactions to an environmental contactant.

Endogenous dermatitis such as atopic, seborrhoeic, varicose and discoid den-natitis, are dermatitis which are genetically inherent skin disorders. They are not caused by environmental agents. However, environmental factors may often aggravate existing endogenous dermatitis.

Irritant Contact Dermatitis

Irritants are substances which directly damage skin at the site of contact or application. Skin inflammation caused by contact with irritants is called irritant contact dermatitis. The inflammation process in irritant contact dermatitis is not mediated through an immunologic mechanism. Irritant contact dermatitis is more common than allergic contact dermatitis. Irritant contact dermatitis is classified into acute irritant dermatitis/reaction and cumulative insult irritant contact dermatitis.

a. Acute irritant dermatitis

Strong irritants e.g. concentrated acids, alkalis or solvents cause an acute irritant contact dermatitis following a single exposure or repeated exposures. The skin structures are damaged directly by the irritant. The cause of acute irritant contact dermatitis is often obvious.

Strong irritants cause irritant contact dermatitis in almost all individuals. In contrast, weak irritants such as water and mild detergents tend to cause irritant contact dermatitis in susceptible individuals only (e.g. individuals with previous atopic dermatitis or hand eczema). Weak irritants tend to cause dermatitis only after repeated skin contact.

In the workplace, cases of acute irritant dermatitis often occur as accidents or as a result of workers' poor work habits e.g. failure to use gloves, boots or aprons when indicated, or from careless handling of acute irritants. It also results from workers' failure (usually due to ignorance) to recognize the hazards of corrosive work materials. Acute iritant dermatitis can very often be prevented and affected workers need not require a job change. Health education is very important here. Where permissible, the use of impervious gloves, aprons and boots during work can prevent acute irritant contact dermatitis.

b. Cumulative insult irritant contact dermatitis

This type of irritant contact dermatitis is caused by repeated skin contact with weak irritants. Weak irritants cause irritant contact dermatitis in susceptible individuals only. The duration between first exposure to the irritant and the appearance of derniatitis varies from weeks to years, depending on the nature of the irritant, frequency of contact, and host susceptibility. The clinical presentation is usually a chronic dermatitis.

Cumulative insult dermatitis is exemplified by the chronic hand dermatitis caused by water and detergents among dishwashers and housewives, and by cutting fluid dermatitis among metalworkers. Solvents such as thinners and kerosene when used inappropriately as skin cleansers often cause cumulative insult dermatitis.

Allergic Contact Dermatitis

Allergic contact dermatitisis an immunologic inflammatory reaction of the skin due to contact with an allergen. In contrast to irritant contact dermatitis, the inflammatory reaction is mediated through an immunological process. An individual does not develop any reaction to the allergen during his initial exposure to the allergen. Often repeat contacts are necessary before an individual becomes sensitized to an allergen. The expression "I have been in contact with the substance for many months and never had any rash with it previously and therefore the substance cannot be the cause of my rash" is a misconception.

Different substances have different sensitizing potential, and there is individual susceptibility to sensitization by an allergen. Once an individual becomes sensitized to an allergen, further contact with the allergen will trigger a type IV hypersensitivity reaction, during which chemical mediators are released from immunocompetent cells, leading to the manifestation of dermatitis. The dermatitis usually appears 36 to 48 hours after contact with the allergen. The dermatitis may be acute, subacute or chronic, depending on the sensitivity of the worker. Allergy to a substance is specific, and once developed, is usually life long.

Common allergens in industry include nickel, fragrances, hexavalent chromate, rubber chernicals and epoxy resins.

Unlike a worker with irritant contact dermatitis, a worker who develops allergic contact dermatitis to a work substance may require a job change. Hence, it is important to differentiate an irritant from an allergic contact dermatitis. Once an allergen has been identified as the cause of occupational dermatitis, it is necessary to inform the worker of the sources of the allergen and to avoid contact with these substances permanently. One must also be aware that "automated processes" need maintenance and workers maintaining such processes are exposed to chemicals used in the automated machines and may also develop contact allergy to the chemicals(11).

Patch Testing

Patch testing is the definitive test for allergic contact dermatitis. The patch test procedure allows the dermatologist to identify the allergen that causes the dermatitis. The patch test procedure consists of applying a set of suspected allergens under occlusion on the skin of the upper back for 48 hours. The reaction to the test allergens is scored after the allergens are removed at 48 hours. A second scoring is made at 96 hours. Patch testing must be carried out by an experienced dermatologist to avoid false positive and false negative test results. For example, a false positive reaction may result if the concentration of the test allergen applied on the skin is too high and a false negative patch test recording may result if the concentration of the test allergen is too low12.

Phototoxic andphotoallergic contact dermatitis

A phototoxic substance is a substance which absorbs ultraviolet light and causes skin inflammation. Examples of phototoxic substances include medicaments (e.g. phenothiazines and tetracyclines), industrial chemicals (e.g. tars) and plant resins. Phototoxic contact dennatitis is not mediated through an immunologic mechanism. The reaction is dose related. Phototoxic substances tend to cause reactions in almost all individuals who are exposed to them.

Photoallergic contact dermatitis, like allergic contact dermatitis, is mediated through an immunological mechanism. The allergen becomes activated only in the presence of ultraviolet light. There is individual susceptibility to photoallergy. Examples of photoallergens include medicaments, fragrances, sunscreens and antiseptics. Photoallergic contact dermatitis can be confirmed by a photopatch test.

Other types of environmentally induced skin disorders

Contact Urticaria

Contact urticaria is an immediate wheal and flare reaction of the skin to a contactant (an urticant). Unlike contact dermatitis, which tends to develop several days after skin contact, contact urticaria develops very soon after skin contact with the urticant. The clinical presentation is usually immediate urticarial eruption (within 30 minutes of contact), and in long standing cases dermatitis. Contact urticaria is not uncommon.

Contact urticaria may be immunologically mediated (type I hypersensitivity reaction = allergic contact urticaria) or non-immunologically mediated. The latter reaction is usually localized and not life-threatening, unlike allergic contact urticaria which can be generalized and lifethreatening. Hence, there is a need to differentiate allergic from non-allergic contact urticaria. Allergic contact urticaria can be confirmed by a skin prick test.

Causes of contact urticaria include foodstuff (e.g. meats, eggs, seafood, vegetables), animal danders and secretions (e.g. from caterpillars and other arthropods), plants and spices (e.g. seaweed, thyme and cayenne pepper), fragrances and flavourings such as Balsam of Peru and cinnamon oil, several types of medicaments (e.g. some antibiotics), metals (e.g. cobalt), some preservatives (e.g. formaldehyde and benzoic acids), and rubber latex (e.g. gloves).

Non-eczenwtous presentations

Other environmental agents, including physical agents (e.g. ionizing radiation, mechanical factors, ultraviolet light, heat, and cold) can damage the skin. Some chemicals are absorbed percutaneously and can cause systemic toxicity (e.g. dioxins causing chloracne). Oils and greases can cause oil acne. Phenolic compounds such as para-tertiary butyl phenol formaldehyde resins may cause skin depigmentation. Table 2 summarizes the causes of non-eczematous presention of occupational dermatoses. Non-eczematous presentations of occupational dermatoses are uncommon. They account for less than 10% of all occupational dermatoses.

Skin cancers

Skin cancers from environmental carcinogens (such as ultraviolet fight, polycyclic aromatic hyderocarbons, and arsenic) are often induced after many years following exposure. In some countries such as in Singapore, statutory regulations require designated factory doctors to undertake special medical examinations of the skin to screen for skin cancers in workers exposed to potential skin carcinogens such as arsenic, tar, pitch, bitumen and creosote.

INDUSTRIES AND OCCUPATIONS AT RISK

Workers in some occupations are at higher risk of developing occupational dermatoses than others. Table 3 lists some industries with risks of occupational dermatoses and some of the commonly encountered occupational irritants and allergens(13).

MANAGEMENT OF OCCUPATIONAL DERMATOSES

An approach to the diagnosis of occupational dermatosis

The diagnosis of an occupational dermatosis requires not only a good knowledge of dermatology, but also a working knowledge of the patient's work process, materials, practice and habits. The clinical appearance of an occupational dermatosis (e.g. dermatitis, acne, skin cancer) is exactly the same as a non-occupational related skin disorder. The danger of overlooking an occupational dermatosis is that the patient's skin problem will recur when he returns to work. The failure to identify and avoid the causative agent of occupational dermatosis at a workplace may also result in failure to recognize similar skin problems in other workers.

It is essential that a detailed occupational history be obtained during any dermatological consultation. Occupational dermatosis should always be suspected when a worker presents with hand dermatitis and dermatitis on the exposed parts, as this is the commonest presentation of an occupational dermatosis. Important elements to look out for in the occupational history and during clinical examination are listed in Table 4.

Additional Information And Follow Up

Occasionally, further information on the nature of the chemicals which are handled by the worker may be required during investigation. The usual way of obtaining such information is to ask the worker for the Material Safety Data Sheets (MSDS) which may be available for the work chemical which is used. The MSDS provides information on the nature of the substance and its possible health effects. Chemical safety and health databases (available either at the Poisons Centres, or Occupational Health Centres) are other sources of information.

Where indicated, samples of the work materials handled by the worker should be obtained for patch testing or for chemical analysis. This may be necessary for the detection of impurities which may not be specified in the information sheet, or detection of decomposition products. The physician may need re arrange for a factory visit to better assess the worker's work conditions, to screen other workers for similar occupational dermatoses or to learn more about the work process.

Specific Management of Occupational Dermatoses

The management of occupational dermatosis depends on its morphological presentation and cause. An accurate diagnosis is essential. The causative agent must be identified. A detailed history, thorough physical examination, and where indicated, relevant investigations including patch tests and laboratory tests together with a factory visit, will often enable the physician to arrive at a correct diagnosis.

The worker should avoid the causative agent immediately if the dermatitis is severe. A temporary job change maybe necessary. Severely affected workers should be given medical leave or hospitalized. Workers with mild dermatosis should be encouraged to resume work with proper pretective garments and advised to observe good work habits.

Dcrmatitis is treated according to its severity. Acute dermatitis should be treated with wet compresses of normal saline or potassium permanganate (1:10,000) lotions until the dermatitis dries up. Chronic dermatitis should be treated with topical steroid creams or ointments of mild to moderate potency (e.g. hydrocortisone, betamethasone valerate, fluocinone acetonide).

Potent steroids such as clobetasol dipropionate should be avoided or used for short periods only because of their potential side effects. It is advisable to avoid combination steroid/anitbiotic/antifungal preparations as they may pose problems of sensitization. Contact allergy to neomycin and quinolines present in such preparations is not uncommon. Oral antibiotics should be administered where secondary bacterial infection is suspected. Oral antihistamines should be given to relieve pruritus.

Other occupational dermatoses are treated according to diagnosis; for example, cutaneous larva migrans with cryotherapy and/or oral antihelmetics, and chromomycosis with oral antifungal agents.

Causes of Chronicity of Occupational Dermatoses

Occasionally, the patient with an occupational dematosis may not respond to treatment. Chronicity of an occupational dermatosis can be due to one or more of the following:

a. Continued exposure to the offending agent.

b. Severe long standing dermatitis which generally takes longer to recover because the barrier functions of the skin are severely impaired.

c. Complications of treatment, such as superimposed contact allergy tomedicaments.

d. Untreated complications, e.g. secondary bacterial infection.

e. Underlying endogenous factors e.g. atopic dermatitis.

f. Medico-legal problems. An avaricious worker may malinger or even self-inflict injury in attempts to seek compensation.

These conditions have to be considered and managed accordingly in a patient with a chronic occupational dermatosis.

Rehabilitation

The primary consideration in the rehabilitation of a worker with occupational dermatosis is to get him back to work as soon as possible, and at the same time prevent a relapse. The worker should be taken off work during the acute stage of the disease, but the physician should not encourage a long absence from work.

Permanent job change should be avoided wherever possible. A job change will require the worker to retrain for another which may be expensive to the employee and the employer. It will also mean social adjustment for the worker - he has to adapt to a new working condition, colleagues and workplace. He may also suffer a salary reduction.

The physician should therefore consider the worker's age, skills, capability, intellect and available preventive measures before recommending a job change. Job change is usually indicated only for workers with allergic contact dermatitis and rarely for those with irritant contact dermatitis. This is because in allergic

contact dermatitis, relapses tend to be more severe witl each subsequent episode and even brief exposure to the allergen will trigger a reaction. However a when substitution of the allergen is possible, or contact with the allergen can be totally avoided by changing work procedures, job change may not be necessary.

Studies have shown that allergic contact dermatitis from some occupational allergens (e.g. chromate from cement, nickel and cobalt) has a poor prognosis". The dermatitis tends to persist even with avoidance of the allergen. Therefore job change may not benefit the worker significantly.

Another important factor to consider before recommending a job change is whether a personal history of atopy is present. Workers with an atopic background, especially those with a history of childhood atopic dermatitis or hand dermatitis, have a higher risk of developing irritant contact dermatitis when they are exposed to irritants. Job counseling is important for these workers, and they should be encouraged to do dry jobs.

The physician must distinguish between medical and social prognosis in workers with occupational dermatoses. Many workers with occupational dermatosis are able to continue work despite their dermatosis. Indeed, many do prefer to remain in their job despite their skin disorder, in order to avoid a salary reduction or a change to a less interesting or challenging job. Some who continue to be exposed to the work irritants or allergens may develop tolerance and hardening.

PREVENTION OF OCCUPATIONAL DERMATOSES

All occupational dermatoses are theoretically preventable. Standard principles of prevention". include substitution or removal of the offending agent, isolation of the worker and enclosure of work process. A well ventilated workplace is desirable when volatile solvents and irritant dusts and fibres are used in the work process.

Pre-placement medical examinations and advice to workers and employers on job suitability (e.g. advising atopics to avoid wet work) and regular health education and training of workers (for hazard awareness, proper handling techniques, and to stress the importance of good personal hygiene) play important roles in prevention.

The availability of conveniently sited washing and drying facilities at the workplace will encourage workers to utilize these facilities during breaks and after work. Proper skin cleansers should be provided, while abrasive detergents and solvents should be removed. The choice of cleanser will depend on the nature of the chemicals handled. A mild soap is usually adequate for office work. Non-aqueous cleansers may be needed to remove grease and oils. Unfortunately, strong cleansers tend to be corrosive and are more likely to cause irritant contact dermatitis.

The habit of using organic solvents and abrasive detergents as skin cleansers must be discouraged. The most effective prevention against occupational dermatitis is to avoid skin contamination during work. It may be better to have slightly dirtied hands than to suffer from chronic dermatitis from vigorous cleansing. Disposable towels should be provided for drying. Emollients or moisturizing creams applied after work may help to restore the barrier function of the skin.

Barrier Creams

The efficacy of barrier creams against occupational dermatitis; is questionable. Most studies have found them to provide limited protection. Workers using barrier creams may have a false sense of security. However, the use of barrier creams has the advantage of increasing the worker's awareness for cleaning their skin during breaks and after work. It also facilitates skin cleansing.

Gloves

Personal protective equipment (e.g. gloves, sleeves, aprons and boots), if properly maintained and correctly used can be a very effective means to prevent occupational dermatoses. One limitation of using gloves is the risk of accidents. The correct type of gloves should be used. The choice of the type of gloves is based on the type of chemical handled and the type of work process. They should cover the distal third of the forearm to be effective. Where dripping of liquid towards the elbow is inevitable, elbow length gloves should be used. Alternatively, the dripping may be prevented by lowering the workbench or elevating the work platform. Impervious gloves are occlusive, and may cause skin maceration. Gloves with a cotton lining may act as a wick and absorb sweat, enhancing a high humidity micro climate adjacent to the skin. Workers should remember to remove gloves periodically and to change them when they become moist or when the inner lining is contaminated. Workers should be provided with several pairs of gloves to change. It should be remembered that workers can occasionally become sensitized to rubber chemicals in rubber gloves, or chromates and resins in leather gloves. Allergic contact dermatitis to gloves and boots is characteristic and should not be overlooked. The use of clean work clothes is also advisable. Skin contact with clothing contaminated by irritants and allergen may cause dermatitis.

Surveillance

The company safety officers, nurses and physician must maintain a vigilant surveillance on the occupational health of their workers so that prompt investigation and management of any outbreaks of occupational dermatoses can be undertaken.

Legislation

Different countries have different medico-legal legislation regulating occupational dermatoses. This may include regulatory laws on environmental standards on cutaneous hazards, the provision of skin hygiene and washing facilities at workplace, notification of occupational dermatoses, statutory medical examinations, and workmen's compensation. Occupational health physicians and nurses, safety officers, general practitioners and anyone responsible for the health care of workers should be familiar with the occupational laws and regulations in their countries.

PERCUTANEOUS ABSORPTION OF TOXINS

The skin is exposed to all environmental elements in the workplace. In addition to being a direct target organ for environmental chemicals, the skin is an important portal of entry of some environmental toxins into the body. The amount and rate of percutaneous absorption of contactants depends on several factors.

Different body sites have different skin permeability to chemicals. There is also individualvariation. Permeability also depends on the state of the skin barrier. Absorption is enchanced through damaged skin or when substances are placed under occlusion. Another factor which affects skin absorption rate is the physical and chemical nature of the chemical, for example, whether it is lipid or non-lipid soluble.

Skin notation in environmental standards

The skin notation is sometimes encountered in environmental standards for toxic agents. This notation serves to highlight the skin as an important portal of entry for the toxin. For example, in the American Conference of Governmental Industrial Hygienists (ACGIH) guide-lines for Threshold LimitValues (TLVs), this notation is described by the ACGIH to "refer to the potential contribution to the overall exposure by the cutaneous route including mucous membranes and eye--either by airborne, or more particularly, direct contact with the substance". It draws attention to the need for having appropriate measures to prevent cutaneous absorption of substances having a "skin notation" so that the TLV is not invalidated.

Thus for chemicals having a skin notation, (important examples of which include solvents and pesticides), respiratory protection alone may be inadequate, even for exposure levels within the prescribed TLVs. It should also be remembered that the skin notation of a chemical only refers to its potential for percutaneous absorption being an important portal of entry into the systemic circulation, and not to the capacity of the substance to cause skin irritation or sensitisation in workers.

CONCLUSION

The skin is an organ which is commonly affected by work related disorders. As such, a good working knowledge of the epidemiology, aetiology, diagnosis, management and rehabilitation of occupational dermatoses is required for the practising health professional.

Occupational dermatoses are preventable. The principle of prevention, which is a major part of the ethos of occupational health practice, should be applied to safeguard the skin of the worker wherever possible.

References

D Koh
MBBS, MSc (OM),
Phl), FFOM, FAMS

C L Goh
MBBS, MMed (Int Med),
FRCP, MD, FAMS