The Industrial Injuries Advisory Council (IIAC) has released an information note on non-melanoma skin cancer (NMSC) and occupational exposure to natural ultraviolet (UV) radiation[i]. An information note on melanoma is also going to be released, as a separate document. In this article, however, we discuss the IIAC’s debate on the proposed addition of NMSC, caused by exposure to occupational sunlight, to the list of prescribed diseases. This was considered in the wake of an enquiry into a former seaman, which was also the basis of the IIAC information note on urolithiasis, above.
‘Primary carcinoma of the skin’, following exposure to arsenic or arsenic compounds, tar, pitch, bitumen, mineral oil (including paraffin) or soot, currently appears on the list of prescribed diseases. The entry on the list does not include skin cancer arising from exposure to sunlight during outdoor working.
The main types of NMSC are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Both are much less dangerous than melanoma, as they are less aggressive and less likely to spread to other parts of the body. Around 3% of SCC spread from the primary site and around 2% cause death. Of the NMSCs, approximately 75% of cases are BCC and the remaining 25% are SCC. Single or multiple SCC and BCC tumours are generally treated successfully with surgical excision, usually with ‘excellent’ or ‘good’ cosmetic results. Any secondary tumours that appear, in the rare event that the cancer spreads, are treated by excision and, in some cases, radiotherapy. Thus, there are likely to be very few cases of NMSC, particularly BCC, that would qualify as being significantly disabling.
Occupational Exposure to Sunlight
Both BCC and SCC are caused by UV radiation from sunlight. However, measuring occupational exposure to sunlight has its difficulties. Different studies apply different methods to estimate sun exposure. Some simply classify workers as outdoor workers without being more specific as to the exposures faced. Other difficulties with measuring sunlight exposure include overestimation, or incorrect/poor recollection of exposure, as well as mitigating factors, such as the optional application of skin protection against UV rays.
The Council noted that studies conducted at lower latitudes than the UK were only indirectly relevant to its decision, as the duration and intensity of UV radiation is much higher in those regions.
Basal Cell Carcinoma of the Skin
The information note refers to a high quality, systematic review of the relationship between BCC risk and occupational UV exposure, published in 2011[ii]. The review included 24 relevant studies that gave considerably varied risk estimates, partly due to latitude. There was some evidence for a dose-response relationship. 2 studies were undertaken at latitudes similar to the UK and showed a doubling of risk. These were examined in more detail by the Council. One of these studies referred to ‘outdoor workers’, but there was no information on the type or duration of such work[iii]. The other study referred to ‘frequent or sometimes’ occupational UV exposure[iv]. Again, there was no mention of the type or overall duration of such employment to clearly gauge the presence of a dose-response relationship.
The Council also conducted a review of the literature published post-2011. Few informative studies were found and were limited by the methods of occupational exposure assessment. A case-control study from Southern Germany reported an increased risk with farming[v], and a case-control study with participants from several European countries found that there was increased risk with farm or construction work of any duration. There was also an increased risk in patients with more than five years of outdoor work experience.[vi]
Squamous Cell Carcinoma of the Skin
The Council found a high quality systematic review and meta-analysis of the risk of SCC with occupational UV exposure, published in 2011[vii]. Similar to the findings for BCC, the risk estimates varied considerably between studies, due, in part, to the quality of exposure assessment and differences in latitude. The Council selected studies from latitudes similar to the UK to analyse in greater depth. In a study of Finnish seafarers, the incidence of BCC and SCC together was increased in those whose cancer was identified 20 or more years after first employment, and in those with 10 or more years on board the vessel[viii]. The risk was more than doubled in male deck officers, but not in male deck crew.
Elsewhere, a Swedish study of more than 320,000 male construction workers found no increased risk of NMSC[ix]. In the group with the highest outdoor exposure, there was an increased risk of lip cancer, but this was not statistically significant. Another study reported a more than doubled risk of SCC with outdoor work, without giving further details of exposure duration. There was also a study from Alberta, Canada, which showed a ‘strong trend toward increasing risk’ of SCC with outdoor occupational exposure[x], while one study reported a more than doubled risk of SCC with outdoor work, but gave no further details about the work or exposure levels[xi]. Nevertheless, a study of workers in several European countries found more than doubled risks of SCC with farm or construction work and with five or more years of outdoor work experience[xii].
As was also the case with BCC, the Council reviewed all literature published since 2011. A very large study from four Nordic countries noted an increased risk of SCC in 14 occupations. However, the risk was more than doubled only in male physicians and female administrators and among these workers, SCC was only diagnosed in subjects under the age of 50[xiii]. There were some increased risk estimates in farmers and seamen, but there was no evidence of increased risk in construction workers, gardeners or forestry workers. In a German study, researchers used a complex job exposure matrix to estimate the lifetime occupational exposure of participants[xiv], but the Council considered this method to be impractical for use in the context of UK benefits assessment.
The Council concluded that it is probable that the risks of both BCC and SCC are augmented by outdoor work, e.g. in the farming and construction industries. In some cases, the risk is more than doubled. It is a precondition of the IIAC that the risk must be doubled for a disease to qualify for addition to the list of prescribed diseases. However, the evidence for these elevated risks comes primarily from countries with more intense UV exposure than the UK; studies from latitudes similar to the UK suggest that the risk is less than doubled.
It is not possible at this stage for the Council to define occupational circumstances that would lead to a doubling of risk. Though some studies suggest that employees in farming, construction and seafaring work may be at an increased risk, no consistent evidence has been found which comprehensively associates risks with the duration of such work.
On this occasion, the Council did not recommend that SCC or BCC, caused by occupational exposure to sunlight, should be added to the list of prescribed diseases.
[i] Non-melanoma skin cancer and occupational exposure to (natural) UV radiation: IIAC information note. Industrial Injuries Advisory Council. 25 April 2018. https://www.gov.uk/government/publications/non-melanoma-skin-cancer-and-occupational-exposure-to-natural-uv-radiation-iiac-information-note/non-melanoma-skin-cancer-and-occupational-exposure-to-natural-uv-radiation-iiac-information-note (Accessed 30 April 2018)
[ii] 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 https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2133.2011.10425.x (Accessed 2 May 2018)
[iii] 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. https://www.ncbi.nlm.nih.gov/pubmed/18649084 (Accessed 2 May 2018)
[iv] 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 https://www.ncbi.nlm.nih.gov/pubmed/15270887 (Accessed 2 May 2018)
[v] 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 https://onlinelibrary.wiley.com/doi/full/10.1111/jdv.12488 (Accessed 2 May 2018)
[vi] 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 https://onlinelibrary.wiley.com/doi/abs/10.1111/jdv.13603 (Accessed 2 May 2018)
[vii] 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. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2133.2010.10118.x (Accessed 2 May 2018)
[viii] Pukkala E, Saarni H. Cancer incidence among Finnish seafarers, 1967-92. Cancer Causes Control. 1996;7(2):231-9 https://link.springer.com/article/10.1007/BF00051299 (Accessed 2 May 2018)
[ix] 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. https://journals.lww.com/epidem/Fulltext/2001/09000/Occupational_Sunlight_Exposure_and_Cancer.15.aspx (Accessed 2 May 2018)
[x] 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 https://jamanetwork.com/journals/jamadermatology/article-abstract/556368 (Accessed 2 May 2018)
[xi] 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. https://link.springer.com/article/10.1007/s00420-008-0342-0 (Accessed 2 May 2018)
[xii] Ibid Trakatelli
[xiii] 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 https://www.jaad.org/article/S0190-9622(16)30018-4/fulltext (Accessed 2 May 2018)
[xiv] 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 https://journals.lww.com/joem/Abstract/2018/01000/Occupational_UV_Exposure_is_a_Major_Risk_Factor.7.aspx (Accessed 2 May 2018)