Independent report

Non-melanoma skin cancer and occupational exposure to (natural) UV radiation: IIAC information note

Published 25 April 2018

© Crown copyright 2018

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Background

1. A former seaman with long service in hot climes developed a basal cell cancer of the skin and contacted the Industrial Injuries Advisory Council (IIAC) to enquire whether he was eligible to make a claim for Industrial Injuries Disablement Benefit (IIDB).

2. The current list of prescribed diseases includes ‘primary carcinoma of the skin’ (PD C21) following exposure to arsenic or arsenic compounds, tar, pitch, bitumen, mineral oil (including paraffin) or soot. It does not include skin cancer arising from exposure to sunlight during the course of outdoor working.

3. In this Information Note we consider the case for prescription of skin cancer in workers with high exposure to natural ultraviolet (UV) radiation in the form of sunlight. Two types of skin cancer are under consideration: basal cell carcinoma (BCC; 75% of cases), commonly known as a ‘rodent ulcer’, and squamous cell carcinoma (SCC; 25%). A third type of skin cancer, melanoma, will be covered in a separate document.

4. It is not uncommon for an individual to have more than one BCC or SCC in separate, primary sites. Single or multiple tumours of either kind are generally treated successfully by surgical excision with, in about 95% of cases, ‘excellent’ or ‘good’ cosmetic results.

5. A small proportion (about 3% of cases) of SCC can spread from their primary site and cause death (2% of total cases); BCC, on the other hand, very rarely does either. ‘Secondary’ tumours of this type are treated by excision and, in some cases, radiotherapy.

6. For the reasons set out in the two preceding paragraphs, the numbers of cases of non-melanoma skin cancer (and in particular BCC) that would qualify as being significantly disabling are likely to be very few.

7. Both, but especially BCC, are incompletely recorded on cancer incidence registries but together they are believed to account for about 20% of all new cancers in the UK. Most registries record only the first BCC or SCC in an individual.

8. The incidence of both BCC and SCC increases with age and each is more common in men; it is believed that there has been an increase in their incidence in both sexes over the past 20 years.

9. Both tumours are caused by UV radiation from natural light and therefore are more common on sun-exposed sites such as the head, ears, neck and backs of the hands. For both types, there is significant modification of risk by skin colour; each is more common in those whose skin burns more easily in sunlight.

Occupational exposure to sunlight

10. There are problems in measuring occupational exposure to sunlight. A very wide variety of indices has been used in the research context (some of which, such as the German ‘standard erythema doses’ (SED) method, would be unsuitable for use in the context of UK benefits assessment). Many studies simply define exposure crudely in terms of ‘work outdoors’. Self-assessment is error prone.

11. A concern in studying occupational skin cancer is that there may be significant recall bias – specifically an affected person (who searches for a reason for their disease) may recall their exposure better than an unaffected person. They may also estimate their recreational sun exposure poorly. The use of skin protection (clothing, sun creams, etc) is similarly difficult to account for in occupational surveys.

12. A further complication in assessing occupational risk is that exposures to sunlight at leisure may be substantial, and not equally distributed by occupation.

13. Studies of populations working at latitudes lower than the UK, where the intensity and duration of UV radiation from the sun are much higher, are only indirectly applicable to working populations covered by the Scheme. The evidence base needs to be read with this consideration in mind.

Basal cell carcinoma (BCC) of the skin

14. A high quality, systematic review of the relationship between BCC risk and occupational exposure to UV radiation was published in 2011[footnote 1]; 24 relevant studies (5 cohort, 19 case-control) were included in the review.

15. The pooled relative risk (RR) from these studies was estimated to be 1.43 (95% confidence interval (95%CI) 1.23-1.66). However, risk estimates varied considerably between studies, in large part because risks vary by latitude, which also differed by study. Cohort and case-control studies generated similar estimates of RR (1.48 and 1.43 respectively), and some evidence was found of a dose-response relationship.

16. The council examined more closely those studies from the review which were of occupations in roughly the same latitude as the UK (about 50-59°) and for which the summary risk estimate was >2.0, the normal threshold for prescription.

17. Only two of these were provided in the review; one described the findings of a linkage between the cancer registry in Bavaria and an employment database [footnote 2]. In both men (RR=2.9, p<0.05) and women (RR=2.7, p<0.05) the risk of BCC was more than doubled in ‘outdoor workers’, but there is no information on the type or duration of such work.

18. The second such study was of 213 men and women with BCC in southern Germany [footnote 3]. The odds that they had had occupational exposure to UV light that was ‘frequent or sometimes’ were increased 2.4-fold (95% CI 1.3–4.70) in comparison to a similar population with no known BCC; again there was no mention of the type or overall duration of such employment.

19. The council conducted a search of the subsequent literature, published between 2011 and 2017; a few studies were informative, although limited by similar imprecision in assessment of the occupational exposure.

20. A further case-control study from southern Germany reported an increased risk associated with farming (adjusted OR>2.0) but provided no information on the required duration(s) of exposure [footnote 4].

21. A case-control study of all types of skin cancer included 602 men and women with BCC from Finland, Germany, Greece, Malta, Spain, Scotland, Italy or Poland [footnote 5]. ‘Outdoor’ workers included farmers (n=538), construction workers (190), sailors (13), forestry workers (14), postmen (14) and 646 ‘others’. After adjustment for confounding exposures, the risk associated with farm or construction work of any duration was 1.83 (95% CI 1.80–2.96). In patients with more than five years of (any) outdoor work the risk was 3.32 (95% CI 2.55–4.33). Country-specific estimates were not presented.

Squamous cell carcinoma (SCC) of the skin

22. As for BCC, the council found a high quality systematic review and meta-analysis of SCC in relation to occupational exposure to sunlight. Published in 2011, it includes 18 relevant studies (6 cohorts) [footnote 6].

23. The pooled RR from these studies was 1.77 (95% CI 1.40-2.22); again, risk estimates varied considerably between studies, driven in part by the quality of exposure assessment and differences in latitude. Again, cohort and case-control studies generated similar estimates of RR (1.68 and 1.77 respectively, each p<0.05).

24. As for BCC, the council examined in more detail those studies from the review that involved populations working at latitudes close to those in the UK.

25. In a study of over 40,000 Finnish seafarers, the incidence of SCC and BCC (together) was increased 1.8-fold (95% CI 1.2-2.5) in those whose cancer was identified 20 or more years after first employment and in those with 10 years or more aboard (95% CI 1.2-2.5). Among male ‘deck officers’ - but not in male ‘deck crew’ - the risk was more than doubled (2.4; 95%CI 1.3-3.9) [footnote 7].

26. In an analysis of over 320,000 men working in the Swedish construction industry, outdoor workers had no increased risk of non-melanoma skin cancer [footnote 8]. The RR for SCC of the lip among those in the highest ‘outdoor exposure’ group was 1.8 (95% CI 0.8–3.7).

27. A case-control study in Alberta, Canada showed only a ‘strong trend toward increasing risk’ of SCC with outdoor occupational exposures [footnote 9].

28. As with BCC, Radespiel-Troger and colleagues (see paragraph 16) report a more-than-doubled risk of SCC in association with ‘outdoor work’ but with no further detail [footnote 2].

29. The case-control study alluded to in paragraph 20 included 406 men and women with SCC from eight European countries [footnote 5]. After adjustment for confounding exposures, the risk associated with farm or construction work was 2.77 (95% CI 1.97–3.88); that for five or more years of ‘outdoor work’ was 3.67 (95% CI 2.63–5.11). As for BCC, no estimates for each country separately were presented.

30. The council undertook a review of the more recent literature and identified a few informative studies. They included the findings of a very large record linkage study in four Nordic countries [footnote 10]. Increased RRs of SCC were reported for 14 occupations but these were more than doubled only in male physicians and nurses and in female administrators (perhaps because of their leisure time exposure to sunlight), and in each case only in those aged less than 50 years at diagnosis. Risk estimates for seven categories of ‘outdoor’ workers were examined in detail. Some estimates in seamen and farmers were elevated (but by no more than 1.5-fold); there was no evidence of an increased risk in construction workers, gardeners or forestry workers.

31. In a case-control study of SCC from Germany [footnote 11] ‘the dosage for a 2-fold increased SCC-risk was … 6,348 SED for lifetime occupational UV exposure’. This study used the complex ‘job-exposure’ matrix mentioned in paragraph 9 which is considered impractical for use in the context of UK benefits assessment. The council subsequently entered into correspondence about the German approach to compensation of skin cancer, but its inquiry has not yielded any usable information.

Summary

It is probable that the risks of both BCC and SCC are increased by outdoor work such as in farming or construction, independently and in some circumstances by more than two-fold. However, the evidence derives very largely from studies of workers in countries at lower latitudes than those in the UK, with consequently higher exposures to UV radiation from sunlight. Indeed, studies from countries at similar latitudes (in particular those of SCC; paragraphs 24-29) suggest that outdoor exposures there are generally insufficient to increase the relative risk by as much as two. Moreover, it is difficult to separate any risks from occupational exposure from those acquired through leisure activities.

A further barrier to prescription for either type of cancer is that the evidence base is not detailed enough to develop a workable definition of the prescription schedule; while certain occupations (notably, farming, seafaring and some construction work) appear to carry an increased risk, no consistent evidence has been found relating risks to the duration of such work. The council does not therefore recommend prescription for either of these skin tumours in respect of occupational exposure to sunlight.

Prevention note

The Health and Safety Executive provides advice on how those work outside can protect their skin from excessive exposure to sunlight www.hse.gov.uk/skin/sunprotect.htm.

 

29 March 2018

 

References

  1. Bauer A, Diepgen TL, Schmitt J. Is occupational solar ultraviolet irradiation a relevant risk factor for basal cell carcinoma? A systematic review and meta-analysis of the epidemiological literature. Br J Dermatol. 2011;165(3):612-25. ↩

  2. Radespiel-Troger M, Meyer M, Pfahlberg A, Lausen B, Uter W, Gefeller O. Outdoor work and skin cancer incidence: a registry-based study in Bavaria. International archives of occupational and environmental health. 2009;82(3):357-63. ↩ ↩2

  3. Walther U, Kron M, Sander S, Sebastian G, Sander R, Peter RU, et al. Risk and protective factors for sporadic basal cell carcinoma: results of a two-centre case-control study in southern Germany. Clinical actinic elastosis may be a protective factor. Br J Dermatol. 2004;151(1):170-8. ↩

  4. Kaskel P, Lange U, Sander S, Huber MA, Utikal J, Leiter U, et al. Ultraviolet exposure and risk of melanoma and basal cell carcinoma in Ulm and Dresden, Germany. J Eur Acad Dermatol Venereol. 2015;29(1):134-42. ↩

  5. Trakatelli M, Barkitzi K, Apap C, Majewski S, De Vries E. Skin cancer risk in outdoor workers: a European multicenter case-control study. J Eur Acad Dermatol Venereol. 2016;30 Suppl 3:5-11. ↩ ↩2

  6. Schmitt J, Seidler A, Diepgen TL, Bauer A. Occupational ultraviolet light exposure increases the risk for the development of cutaneous squamous cell carcinoma: a systematic review and meta-analysis. Br J Dermatol. 2011;164(2):291-307. ↩

  7. Pukkala E, Saarni H. Cancer incidence among Finnish seafarers, 1967-92. Cancer Causes Control. 1996;7(2):231-9. ↩

  8. Hakansson N, Floderus B, Gustavsson P, Feychting M, Hallin N. Occupational sunlight exposure and cancer incidence among Swedish construction workers. Epidemiology (Cambridge, Mass). 2001;12(5):552-7. ↩

  9. Gallagher RP, Hill GB, Bajdik CD, Coldman AJ, Fincham S, McLean DI, et al. Sunlight exposure, pigmentation factors, and risk of nonmelanocytic skin cancer. II. Squamous cell carcinoma. Arch Dermatol. 1995;131(2):164-9. ↩

  10. Alfonso JH, Martinsen JI, Pukkala E, Weiderpass E, Tryggvadottir L, Nordby KC, et al. Occupation and relative risk of cutaneous squamous cell carcinoma (cSCC): A 45-year follow-up study in 4 Nordic countries. J Am Acad Dermatol. 2016;75(3):548-55. ↩

  11. Schmitt J, Haufe E, Trautmann F, Schulze HJ, Elsner P, Drexler H, et al. Occupational UV-Exposure is a Major Risk Factor for Basal Cell Carcinoma: Results of the Population-Based Case-Control Study FB-181. Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine. 2018;60(1):36-43. ↩

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