Current Approaches to Occupational Health: Volume 3

Current Approaches to Occupational Health deals with problems and progress in relation to occupational health. This book is organized into 21 chapters written by different contributors. The occupational health issues covered by these chapters include ethical problems in occupational medicine, the role of legislation, regulation and enforcement in occupational health, the monitoring of occupational risks for cancer and the identification and intervention for problem drinkers at work. This book will be of interest to occupational health students and practitioners and to other medical professionals.

• Language: English
• Publisher: Elsevier Science
• Release date: Oct 22, 2013
• ISBN: 9781483193502

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Industry.

1

LOW-HUMIDITY OCCUPATIONAL DERMATOSES

R.J.G. Rycroft

Publisher Summary

This chapter focuses on low-humidity occupational dermatoses. Low-humidity occupational dermatoses are because three reasons—(1) the annoyance and anxiety caused by itching can be out of all proportion to the visible signs of skin dryness; (2) the exigency of symptoms may lead to a large amount of time and money being spent on the investigation of other possible causes such as allergy; and (3) the condition once diagnosed is usually amenable to remarkably simple and inexpensive measures. These skin problems are a prime example of the value in occupational medicine of making oneself as familiar as possible with the details of the working environment. There are several factors that may complicate a primarily low-humidity dermatosis, in addition to local heat sources and sharp or hygroscopic particles.

An attractive young lady, who has had mild eczema since childhood, starts work as a receptionist in a large hotel. Her eczema gets gradually worse the longer she works there. A harassed-looking middle-aged businessman, involved in a take-over bid, itches all over after a hectic schedule of flights back-and-forth across the Atlantic. An ageing handyman in a modern electronics factory has a patchy facial eczema. It seems to have come up during a winter in which his redundancy has been on the cards. At first sight, the suggestion that there might be a common factor between all three of these skin problems seems improbable—unless perhaps it was stress. Yet these cases all resulted from the low humidity of indoor environments: hotel, aeroplane and factory. How could this be?

Below a water content of 10 per cent the outer tissue-paper-thin layer of the skin, the stratum corneum or horny layer, loses its softness and pliability.¹ The water content of the horny layer stays below 10 per cent when the relative humidity is less than around 50 per cent (relative humidity is the ratio of the actual vapour pressure of water to the saturated vapour pressure of water at the same temperature, expressed as a percentage). Drying out of the horny layer occurs most rapidly under conditions of high temperature, low humidity and fast-flowing air. The first two, and sometimes all three, of these conditions now occur in a large number of modern working environments.

It has therefore become necessary to recognize the effects of such working conditions on the skin. Those that are seen can roughly be divided into three: itching (pruritus), whealing (urticaria), and reddened flaky rashes (eczema). Dermatologists have long recognized similar, though not identical, skin problems arising from cold dry winter weather. Terms such as ‘winter itch’ have been coined to describe these related phenomena. The conditions arising from warm dry indoor working environments can conveniently be termed low-humidity occupational dermatoses.²

One point needs stressing at the outset. Low-humidity occupational dermatoses are more important than they might seem. There are at least three reasons for this. First, the annoyance and anxiety caused by itching can be out of all proportion to the visible signs of skin dryness. This can be highly destructive of good industrial relations. Second, the exigency of symptoms may lead to a large amount of time and money being spent on the investigation of other possible causes such as allergy. Last, the condition once diagnosed is usually amenable to remarkably simple and inexpensive measures. No one can afford to ignore this unstable borderland between skin physiology and pathology.

These skin problems are a prime example of the value in occupational medicine of making oneself as familiar as possible with the details of the working environment. It is far more difficult to make the diagnosis on an individual patient in a medical department than it is from looking at employees together as a group. But a warning is due. Time spent in reconnaissance is seldom if ever wasted: the problem should always be well considered from other angles before deciding on low humidity as the sole cause. It is not unusual, for example, for low humidity to be only one of two or more factors involved in an occupational dermatosis.

This chapter is intended to equip its readers with a realistic index of suspicion for low-humidity effects on the skin at work; to acquaint them with environments in which such problems may arise; and to indicate the ways in which the skin condition can be corrected. A number of other common disorders are discussed under differential diagnosis, since it is just as important not to over-diagnose this factor as it is to recognize it when it is there. From time to time I have imposed on the reader some point of general principle in occupational dermatology that seems to me to be illustrated by particular aspects of the outbreaks described. This is intended to broaden the usefulness of the discussion without, I hope, distracting from the subject at hand.

PRURITUS

The skin can itch following quite minor physiological alterations.³ Individual itch thresholds vary widely. Atopics, for example, may relatively easily be stimulated to itch. A typical example of an outbreak of pruritus being caused by warm dry flowing air was provided by the introduction of hot unhumidified air downwards through a continuous vent around the periphery of an open-plan office. Complaints of itching came particularly from clerks sitting directly beneath this vent, though they came to a lesser extent from clerks working on the rest of the floor.

The worst case in this epidemic was that of a young female who already had atopic eczema, but whose skin was made very much worse by this environment. Beware of accepting such a case as typical: the remainder of the clerks had skin appearances varying from mild to scarcely detectable dryness (asteatosis or xerosis) and flaking (scaling).

It is not unusual for the worst case or cases in an outbreak of an occupational dermatosis to be atypical or even irrelevant to the more general problem. The occupational health practitioner should be reluctant to allow his clinical assessment of a widespread skin problem at work to rely too exclusively on the examination of the two or three worst cases, especially if they are self-selected or chosen by a representative without medical or nursing training. By all means examine such patients first, but then follow this up by talking to, and looking briefly at, as many other members of the working group as their cooperation—and your time—allows.

PRURITUS AND URTICARIA

Low-humidity occupational dermatoses do not only occur in offices. Ten years ago I was asked to investigate gathering complaints of severe pruritus and mild urticaria among men installing international telephone exchange equipment in a purpose-built new building.² The discrepancy between ‘ten years ago’ and the publication date of the reference just given, 1980, is a telling example of just how long it can take an unprepared mind to identify the real cause of an occupational skin problem. The problem eventually had to solve itself and, because all investigated causes had previously been rejected, the file on the problem had been kept open until that time. This at least allowed me to learn from my failure to identify the cause myself.

The alternative possible causes that I had previously investigated with essentially negative results are not uninstructive, since they adumbrate the range of conditions that may have to be considered in the differential diagnosis. The skin complaints comprised urticarial wheals and involved predominantly areas of skin covered by clothing, including the lower limbs.

Inhalable and ingestible allergens were considered. I well remember a searching examination that I made of the works canteen in pursuit of potentially allergenic foods. Glass fibre from filters within the air conditioning system was looked for in air samples: so near geographically, and yet still so far away mentally, did the investigation get to the source of the problem. Powder released from within electronic cables came under suspicion. Even psychological stress, such as might be induced by fear of redundancy after the contract was finished, was entertained as a possible explanation.

While these investigations continued, at a variable pace according to the pressure of other investigations, the situation progressively deteriorated. Much to my embarrassment the number of cases continued to rise. After a while, my secretary was scarcely able to bring herself to tell me that the company nurse was on the telephone again. During the summer of 1977 symptoms seemed to subside but such temporary alleviations can never be depended on: the autumn of 1977 saw a resurgence. I was fortunate enough to undertake a year’s work in the USA at this juncture, though I must insist that the two events were totally unconnected.

By my return from the USA the problem was solved. This occurred when, following completion of the exchange equipment installation, the itching men no longer had to work for long periods in the carefully-controlled environment of the telephone exchange equipment. To prevent corrosion of metal contacts, temperature and humidity had been controlled within narrow limits by a double air-conditioning system: a central system supplying humidified air all year round, and a peripheral system supplying warm, unhumidified air during the winter months.

It was around the periphery of the telephone exchange floor that the worst-affected men had their temporary offices and it was in winter that their symptoms had been at their peak. The relative humidity around them had been approximately 35 per cent when they had been most symptomatic: their symptoms resolved when they eventually escaped into a relative humidity of 50 per cent and above.

Following this change, no further new cases presented and even previously persistent cases rapidly cleared up. The urticaria appeared to have been secondary to the scratching of itchy, dry skin, no doubt exacerbated by the men’s natural frustration at the failure of their appointed investigator to work out the answer to their problem.

LOW-GRADE ECZEMA

In 1972 the Vancouver dermatologist, John Mitchell, justly renowned for his work in the great outdoors on plant dermatitis, reported a small but effective study that he had instigated in his own hospital.⁴ He had noted that older male in-patients in the Shaughnessy Veterans Hospital frequently developed xerosis of the skin and mild eczemas. The relative humidity in the skin ward and two medical wards was measured during December and January. In all three wards the relative humidity varied between 20 and 40 per cent. The relative humidity of the air in one of the medical wards at 8.15 a.m. on 21 January was 16 per cent and the temperature 81°F (27°C). Mitchell commented, appropriately enough: These conditions may also prevail, I understand, in the Sahara desert.’

I have encountered at least ‘semi-desert’ conditions in factories manufacturing silicon chips and soft contact lenses. Since the first of these episodes, it has become clear that low humidity is a widespread problem in the new electronics industries where dry air is protective to the products during manufacture. In a silicon chip factory investigated early in 1979² the face was the sole site of complaints.

Four female process operators, all in their forties and fifties, had persistently complained of irritation and redness of their faces that winter. Their symptoms and signs had variably been ascribed by doctors to rosacea, the menopause, and even the combination of alcohol ingestion and trichloroethylene inhalation known as ‘degreaser’s flush’,⁵ because of their proximity at work to degreasing tanks. The latter two explanations, with their veiled implications respectively of sexism and alcoholism, were understandably not well accepted by the four women. Also, they had already found out for themselves that oral tetracycline did not cure their ‘rosacea’, whereas their own moisturizing creams had been surprisingly helpful. Their confidence in the medical profession had fallen to a low ebb.

Clinically, they all showed patchy redness and scaling over their cheeks and foreheads. Three had fair complexions and skins previously damaged by sun exposure (telangiectasia and elastosis). They all four worked at the same bench in one corner of the factory. They scored (scribed) lines between individual silicon chips in a block, separated (cracked) the chips along these scored lines, and finally subjected them to close visual inspection. This visually-demanding scribing and cracking required intense local illumination. In addition, vacuum pumps held chips in place for inspection; chips were stored in heated cabinets above the bench; and a diffusion furnace behind the bench was regularly checked for temperature through open doors. All these electrical devices were local sources of radiant or convective heat.

The reader will not be surprised to learn that the mean air temperature in this mini-environment was found to be a little over 77°F (25°C) and the relative humidity to average 35 per cent. While comparatively good conditions perhaps for the Shaughnessy Veterans Hospital male medical wards, they were still bad enough to dehydrate the facial skin of these scribers-and-crackers. The problem was solved when the relative humidity was raised with humidifiers so that it was at least 45 per cent in this corner and when the women made their use of moisturizing cream routine.

Complaints of facial itching in a soft contact lens factory reached epidemic proportions in the winter months of 1981.⁶ By early April, 72 per cent of 78 mainly female employees examined showed patchy or diffuse superficial scaling of the facial skin, most noticeable on the cheeks, but also visible on the forehead, nose and neck. This scaling was frequently associated with a mild redness. Blondes were involved in a higher proportion than brunettes. Some had little in the way of signs, but much more in the way of symptoms. The shaven cheeks and chins of male employees tended to show a patchy redness without scaling, the scales presumably having been removed with the stubble.

Their large workroom was found to be air-conditioned rigorously, in order to protect the special acrylic polymer from which the soft contact lenses were machined. This hard polymer absorbs water and, when it does, swells and becomes soft, just like the horny layer of the skin. The ambient air was deliberately kept dry to prevent the polymer prematurely absorbing water from the atmosphere, and thus altering its dimensions during machining. Relative humidity and temperature in the workroom were continuously monitored. The answer to the problem had therefore already been plotted on a paper strip which was immediately available for inspection. The occupational hygienist is not often lucky enough to find his work already done for