METHODS

Methods for the surveillance of occupational skin disease have been described previously.¹⁷ In February 1994, all British consultant dermatologists, then numbering 244, reported incident cases of occupational skin disease to the EPIDERM surveillance scheme at the University of Manchester. The scheme was redesigned in January 1996, so that a “core group”, currently comprising 24 dermatologists with a special interest in occupational skin disease reported monthly, with the remaining “sample group” of all other UK dermatology consultants reporting cases seen during a specified calendar month of the year. The estimated yearly rate for the whole sample group was calculated by applying a multiplier of 12 to the reports obtained by monthly sampling. This figure was combined with the cases that had been reported monthly by the core physicians over the 12 month period in order to give estimated yearly figures for the whole group.¹⁷ Potentially, the whole population of the UK covered by the NHS, is included.

Participating dermatologists complete a reporting card for the month(s) in question, even if they had not seen a case of occupationally related illness during that month. Late responders were reminded by telephone or fax. On the reporting card, information was requested on seven categories of occupational skin disease. Details requested on each case included initials, sex, date of birth, abbreviated postcode, job, industry, and suspected agent(s). Patch tests in participating centres were performed in a standardised way,¹⁸ with a standard series including nickel.¹⁸ An allergen giving a positive allergic patch test was included if judged to be relevant occupationally in that particular case, as would be the case if there was known and more than transitory occupational contact with that substance. The British Association of Dermatologists has given some guidance on assessing relevancy.¹⁸

From July 1997 onwards, in order to better understand the possible occupational role of nickel, dermatologists were asked to indicate all positive patch tests to nickel in all cases of occupational contact dermatitis (OCD) reported, and to indicate whether or not nickel was believed to be of any relevance to the causation of the OCD.

Occupational physicians in the UK were included in the surveillance scheme from May 1994, and for the first 17 months reported every new case of occupational skin disease. In January 1996, OPRA was initiated and, from that point, medical inspectors from the Health and Safety Executive (currently numbering 18) reported cases monthly, while the other occupational physicians (currently numbering 772) only reported cases seen during one of 12 specified calendar months of the year.¹⁷ The OPRA reporting card includes the category “contact dermatitis”, and occupational physicians are asked to list suspected agents, in the vast majority of cases without support from patch tests. Annual totals were estimated as in EPIDERM. In each scheme, duplicate reports were identified and eliminated by searching the database for initials, date of birth, and postcode, so no case was counted twice. For calculation of rates, denominators were obtained from the Labour Force Survey.¹⁹ Because of the start date in February 1993, all surveillance dates shown by calendar year (for example, 1993) cover the 12 months from 1 February in that year to 31 January in the following year.

RESULTS

From February 1993 to January 1999, an estimated 12 574 cases of occupational skin disease were reported by dermatologists (EPIDERM), of which 9937 (79%) were OCD. In 1190 cases (12% of OCD reported), nickel was one of the suspect agents (mean 198 cases/year; 912 females, 278 males; F:M ratio 3.3:1). Occupational physicians reported an estimate of 10 136 new cases of occupational skin disease in the period May 1994 to January 1999 (OPRA). Of these, 8129 were OCD (80%), of which 157 (1.9%) were thought to be due at least in part to nickel (mean 33/year; 107 females, 50 males; F:M ratio 2.1:1). There are yearly fluctuations in period prevalences, but there is no consistent trend with time (fig 1). The frequency of occupational nickel dermatitis for women decreased with age, with the highest rates seen in the 16–30 year age group in both schemes (fig 2). There was no age pattern for men, although a slight increase is seen with increasing age in dermatologists’ reports.

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Figure 1

Occupational contact dermatitis attributed to nickel. Yearly estimated numbers of cases from dermatologists (DERM) and from occupational physicians (OP) by year. (For 1994, figures from occupational physicians include only cases from May, when reporting began, to January.)

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Figure 2

Rates of occupational contact dermatitis attributed to nickel by age and sex, per million employed per year. Estimates from dermatologists (EPIDERM: Feb 1993–Jan 1999) and occupational physicians (OPRA: May 1994–Jan 1999).

The occupations most frequently reported by dermatologists (EPIDERM) as believed to show an association between nickel exposure at work and OCD are hairdressers, cleaners, and cooks, with the highest rates (based on numbers employed in the occupation) in hairdressers, bar staff, and cooks (table 1). Occupational physicians (OPRA) report the most frequent occupations to be electronic assemblers (24 cases), nurses (16), sales assistants (14), and general assemblers (12). Most cases reported by dermatologists were viewed as allergic contact dermatitis (62% of cases) or mixed allergic and irritant dermatitis (26%), with 7% regarded as primarily an irritant contact dermatitis (nickel contact allergy playing a secondary role) and 5% not specified.

From July 1997 to January 1999, dermatologists (EPIDERM) reported 547 patients (436 females, 111 males) with patch tests positive for nickel, of which 195 (36%) were thought to have nickel dermatitis arising from, or made worse by, work. Among women, hairdressers had the highest number of allergic positive patch tests to nickel but, in all except two cases, this was only one of several agents reported, and nickel was felt to be relevant (in terms of occupational exposure being likely and sufficient) in only 19% (table 2). In the small number of subjects whose occupations involved handling coins and who were reported to have occupational dermatitis, nickel was often reported to be the sole agent.

DISCUSSION

This report from the EPIDERM and OPRA surveillance schemes provides the national data from the UK on cases of occupational dermatitis that were believed to be associated with exposure to nickel. In most epidemiological surveillance schemes, except the information network of departments of dermatology (IVDK) in Germany,²¹ there is some form of estimation from sample groups and our data are therefore comparable with those collected in other countries. OCD associated with nickel exposure accounted for 12% of cases reported by dermatologists, but only 2% of cases reported by occupational physicians. This difference may reflect the different population presenting to the two specialties. Those working in smaller or poorly regulated industries often have no access to an occupational health service and present instead to general practitioners and then to dermatologists. In addition, occupational physicians do not generally perform patch tests; this may mean an under-reporting of figures for occupational dermatitis associated with nickel exposure. With regard to the reporting systems, for future reference better definition of relevance of patch test results and for assessing causation would help improve the quality of the data collection.

Nickel sensitivity is common,²² usually being acquired through ear piercing,^24,25 and its role in occupational dermatitis is difficult to assess. Some authors believe that, in up to 25% of nickel allergic patients, nickel may be an important occupational allergen.^15,23,24 In the second part of the study, when reporters were asked to identify nickel allergy, whether coincidental or causational, in patients being reported with an OCD, nickel was judged by the reporting dermatologist to be an associated factor in the OCD in 36% of cases. It is important to note that in most cases (64%), nickel was not considered relevant despite the positive patch test. This was the case in occupations such as hairdressers and beauticians, nurses, food handlers, and floral arrangers in which other occupational agents were identified. In these instances, nickel was regarded as relevant to the causation of the dermatitis in fewer than 50% of those who had a positive patch test. On the other hand, although numbers are small, positive patch tests to nickel were felt to be relevant to OCD in people who handle coined money, including counter clerks, cashiers, cash and check out operators, in most of whom no other occupational factor was identified. In some jobs, such as sales assistant, the incidence of OCD with associated occupational exposure to nickel reported by dermatologists is low (0.8/100 000 sales assistants), but this may represent a large number of cases because it is a common job. Conversely, for other work, the incidence is high (for example, 11.4/100 000 for beauticians), but the numbers may be lower because there are fewer employed.

In some groups, such as metal workers and electroplaters, it is agreed that occupational exposure can play a major part in the causation of dermatitis,^7,15 although pre-existing nickel sensitivity has been shown in up to 88%.⁷ Exposure to irritants and wet work impair the barrier function of the skin and may make sensitisation to nickel more likely, with worsening of the dermatitis.⁷ In other workers such as hairdressers, cleaners, cashiers, shop assistants, and caterers, there is a potential for occupational nickel exposure, but workplace levels of exposure are difficult to quantify and the contribution of nickel to OCD hard to assess. Hairdressers do have contact with instruments that contain nickel, and these have been shown to release nickel on exposure to permanent wave fluids,²⁶ but with the current use of stainless steel instruments, the nickel release will be less. In cleaning jobs, used water and cloths have been shown to contain appreciable amounts of nickel.¹⁰ Cashiers, counter clerks, and shop assistants handle nickel containing coins,^14,27 and caterers and catering assistants come into contact with metal objects, some of which release nickel.²⁸

CONCLUSIONS

In a small number of cases, reporters to EPIDERM considered that nickel exposure from coin handling, in the absence of other sensitising exposures, may be a contributor to OCD. European Union regulations^29,30 limit the amount of nickel released from products which come into prolonged contact with the skin (to 0.5 μg/cm²/week), but some nickel sensitive patients may still react to this level of nickel exposure.²⁹ In Denmark, these regulations began in 1991 and a decrease in the frequency of nickel allergy in children has already been shown.³¹ The relevance of occupational exposure to nickel to the causation of OCD will only be assessable when workplace measurements are possible and thresholds for reactivity defined.