The effects of exposure to solar radiation on human health.

This assessment by the Environmental Effects Assessment Panel (EEAP) of the Montreal Protocol under the United Nations Environment Programme (UNEP) evaluates the effects of ultraviolet (UV) radiation on human health within the context of the Montreal Protocol and its Amendments. We assess work published since our last comprehensive assessment in 2018. Over the last four years gains have been made in knowledge of the links between sun exposure and health outcomes, mechanisms, and estimates of disease burden, including economic impacts. Of particular note, there is new information about the way in which exposure to UV radiation modulates the immune system, causing both harms and benefits for health. The burden of skin cancer remains high, with many lives lost to melanoma and many more people treated for keratinocyte cancer, but it has been estimated that the Montreal Protocol will prevent 11 million cases of melanoma and 432 million cases of keratinocyte cancer that would otherwise have occurred in the United States in people born between 1890 and 2100. While the incidence of skin cancer continues to rise, rates have stabilised in younger populations in some countries. Mortality has also plateaued, partly due to the use of systemic therapies for advanced disease. However, these therapies are very expensive, contributing to the extremely high economic burden of skin cancer, and emphasising the importance and comparative cost-effectiveness of prevention. Photodermatoses, inflammatory skin conditions induced by exposure to UV radiation, can have a marked detrimental impact on the quality of life of sufferers. More information is emerging about their potential link with commonly used drugs, particularly anti-hypertensives. The eyes are also harmed by over-exposure to UV radiation. The incidence of cataract and pterygium is continuing to rise, and there is now evidence of a link between intraocular melanoma and sun exposure. It has been estimated that the Montreal Protocol will prevent 63 million cases of cataract that would otherwise have occurred in the United States in people born between 1890 and 2100. Despite the clearly established harms, exposure to UV radiation also has benefits for human health. While the best recognised benefit is production of vitamin D, beneficial effects mediated by factors other than vitamin D are emerging. For both sun exposure and vitamin D, there is increasingly convincing evidence of a positive role in diseases related to immune function, including both autoimmune diseases and infection. With its influence on the intensity of UV radiation and global warming, the Montreal Protocol has, and will have, both direct and indirect effects on human health, potentially changing the balance of the risks and benefits of spending time outdoors.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2021.

The Environmental Effects Assessment Panel of the Montreal Protocol under the United Nations Environment Programme evaluates effects on the environment and human health that arise from changes in the stratospheric ozone layer and concomitant variations in ultraviolet (UV) radiation at the Earth's surface. The current update is based on scientific advances that have accumulated since our last assessment (Photochem and Photobiol Sci 20(1):1-67, 2021). We also discuss how climate change affects stratospheric ozone depletion and ultraviolet radiation, and how stratospheric ozone depletion affects climate change. The resulting interlinking effects of stratospheric ozone depletion, UV radiation, and climate change are assessed in terms of air quality, carbon sinks, ecosystems, human health, and natural and synthetic materials. We further highlight potential impacts on the biosphere from extreme climate events that are occurring with increasing frequency as a consequence of climate change. These and other interactive effects are examined with respect to the benefits that the Montreal Protocol and its Amendments are providing to life on Earth by controlling the production of various substances that contribute to both stratospheric ozone depletion and climate change.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020.

This assessment by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) provides the latest scientific update since our most recent comprehensive assessment (Photochemical and Photobiological Sciences, 2019, 18, 595-828). The interactive effects between the stratospheric ozone layer, solar ultraviolet (UV) radiation, and climate change are presented within the framework of the Montreal Protocol and the United Nations Sustainable Development Goals. We address how these global environmental changes affect the atmosphere and air quality; human health; terrestrial and aquatic ecosystems; biogeochemical cycles; and materials used in outdoor construction, solar energy technologies, and fabrics. In many cases, there is a growing influence from changes in seasonality and extreme events due to climate change. Additionally, we assess the transmission and environmental effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the COVID-19 pandemic, in the context of linkages with solar UV radiation and the Montreal Protocol.

Clinical utility of skin cancer and melanoma risk scores for population screening: TRoPICS study.

BACKGROUND: Screening for skin cancer can be cost-effective if focused on high-risk groups. Risk prediction tools have been developed for keratinocyte cancers and melanoma to optimize advice and management. However, few have been validated in a clinical setting over the past few years. OBJECTIVES: To assess the clinical utility of risk assessment tools to identify individuals with prevalent skin cancers in a volunteer-based screening clinic. METHODS: Participants were adults presenting for a skin check at a volunteer-based skin cancer screening facility. We used previously published tools, based on questionnaire responses, to predict melanoma and keratinocyte cancers [KCs; basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)] and classified each participant into one of five risk categories. Participants subsequently underwent a full skin examination by a dermatologist. All suspicious lesions were biopsied, and all cancers were histopathologically confirmed. RESULTS: Of 789 people who presented to the clinic, 507 (64%) consented to the study. Twenty-two BCCs, 19 SCCs and eight melanomas were diagnosed. The proportion of keratinocyte cancers diagnosed increased according to risk category from <1% in the lowest to 24% in the highest risk category (P < 0.001). Subtype analysis revealed similar proportionate increases in BCC or SCC prevalence according to risk category. However, a similar proportion of melanoma cases were detected in the low-risk and high-risk groups. CONCLUSION: The risk prediction model for keratinocyte cancers can reliably identify individuals with a significant skin cancer burden prior to a skin examination in the community setting. The prediction tool for melanoma needs to be tested in a larger sample exposed to a wider range of environmental risk factors.

Environmental effects of stratospheric ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2019.

This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595-828), of recent findings of current and projected interactive environmental effects of ultraviolet (UV) radiation, stratospheric ozone, and climate change. These effects include those on human health, air quality, terrestrial and aquatic ecosystems, biogeochemical cycles, and materials used in construction and other services. The present update evaluates further evidence of the consequences of human activity on climate change that are altering the exposure of organisms and ecosystems to UV radiation. This in turn reveals the interactive effects of many climate change factors with UV radiation that have implications for the atmosphere, feedbacks, contaminant fate and transport, organismal responses, and many outdoor materials including plastics, wood, and fabrics. The universal ratification of the Montreal Protocol, signed by 197 countries, has led to the regulation and phase-out of chemicals that deplete the stratospheric ozone layer. Although this treaty has had unprecedented success in protecting the ozone layer, and hence all life on Earth from damaging UV radiation, it is also making a substantial contribution to reducing climate warming because many of the chemicals under this treaty are greenhouse gases.

Does polygenic risk influence associations between sun exposure and melanoma? A prospective cohort analysis.

BACKGROUND: Melanoma develops as the result of complex interactions between sun exposure and genetic factors. However, data on these interactions from prospective studies are scant. OBJECTIVES: To quantify the association between ambient and personal ultraviolet exposure and incident melanoma in a large population-based prospective study of men and women residing in a setting of high ambient ultraviolet radiation, and to examine potential gene-environment interactions. METHODS: Data were obtained from the QSkin Sun and Health Study, a prospective cohort study of men and women aged 40-69 years, randomly sampled from the Queensland population in 2011. Participants were genotyped and assessed for ultraviolet exposure. RESULTS: Among participants with genetic data (n = 15 373), 420 (2·7%) developed cutaneous melanoma (173 invasive, 247 in situ) during a median follow-up time of 4·4 years. Country of birth, age at migration, having > 50 sunburns in childhood or adolescence, and a history of keratinocyte cancer or actinic lesions were significantly associated with melanoma risk. CONCLUSIONS: An interaction with polygenic risk was suggested: among people at low polygenic risk, markers of cumulative sun exposure (as measured by actinic damage) were associated with melanoma. In contrast, among people at high polygenic risk, markers of high-level early-life ambient exposure (as measured by place of birth) were associated with melanoma (hazard ratio for born in Australia vs. overseas 3·16, 95% confidence interval 1·39-7·22). These findings suggest interactions between genotype and environment that are consistent with divergent pathways for melanoma development. What's already known about this topic? The relationship between sun exposure and melanoma is complex, and exposure effects are highly modified by host factors and behaviours. The role of genotype on the relationship between ultraviolet radiation exposure and melanoma risk is poorly understood. What does this study add? We found that country of birth, age at migration, sunburns in childhood or adolescence, and history of keratinocyte cancer or actinic lesions were significantly associated with melanoma risk, while other measures of continuous or more intermittent patterns of sun exposure were not. We found evidence for gene-environment interactions that are consistent with divergent pathways for melanoma development. Linked Comment: Cust. Br J Dermatol 2020; 183:205-206. Plain language summary available online.

The effect of sunscreen on vitamin D: a review.

BACKGROUND: Sunscreen use can prevent skin cancer, but there are concerns that it may increase the risk of vitamin D deficiency. OBJECTIVES: We aimed to review the literature to investigate associations between sunscreen use and vitamin D3 or 25 hydroxyvitamin D [25(OH)D] concentration. METHODS: We systematically reviewed the literature following the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. We identified manuscripts published in English between 1970 and 21 November 2017. Eligible studies were experimental [using an artificial ultraviolet radiation (UVR) source], field trials or observational studies. The results of each of the experimental studies and field trials are described in detail. Two authors extracted information from observational studies, and applied quality scoring criteria that were developed specifically for this question. These have been synthesized qualitatively. RESULTS: We included four experimental studies, three field trials (two were randomized controlled trials) and 69 observational studies. In the experimental studies sunscreen use considerably abrogated the vitamin D3 or 25(OH)D production induced by exposure to artificially generated UVR. The randomized controlled field trials found no effect of daily sunscreen application, but the sunscreens used had moderate protection [sun protection factor SPF) ~16]. The observational studies mostly found no association or that self-reported sunscreen use was associated with higher 25(OH)D concentration. CONCLUSIONS: There is little evidence that sunscreen decreases 25(OH)D concentration when used in real-life settings, suggesting that concerns about vitamin D should not negate skin cancer prevention advice. However, there have been no trials of the high-SPF sunscreens that are now widely recommended. What's already known about this topic? Previous experimental studies suggest that sunscreen can block vitamin D production in the skin but use artificially generated ultraviolet radiation with a spectral output unlike that seen in terrestrial sunlight. Nonsystematic reviews of observational studies suggest that use in real life does not cause vitamin D deficiency. What does this study add? This study systematically reviewed all experimental studies, field trials and observational studies for the first time. While the experimental studies support the theoretical risk that sunscreen use may affect vitamin D, the weight of evidence from field trials and observational studies suggests that the risk is low. We highlight the lack of adequate evidence regarding use of the very high sun protection factor sunscreens that are now recommended and widely used.

Aspirin and nonsteroidal anti-inflammatory drug use and keratinocyte cancers: a large population-based cohort study of skin cancer in Australia.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) have been postulated as chemopreventive agents for basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), but findings from observational studies have been inconsistent, and clinical trial data are scant. OBJECTIVES: To examine the association between aspirin and NSAID (nonaspirin) use and the risk of BCC and SCC in a large cohort specifically designed for skin cancer outcomes. METHODS: We used data from the QSkin Study, a prospective cohort of 43 764 residents of Queensland, Australia (34 630 were included in this study and 23 581 were used in our primary analyses). We used Cox proportional hazards models to estimate the hazard ratios (HRs) between self-reported aspirin and NSAID use 1 year prior to study baseline and the first histologically confirmed BCC or SCC for high-risk (history of skin cancer excisions or more than five actinic lesions treated) and average-to-low-risk participants (no history of skin cancer excision and at most five actinic lesions treated). RESULTS: After a median of 3 years of follow-up, 3421 participants developed BCC and 1470 SCC (2288 BCC and 932 SCC with complete covariate information). Among the high-risk group (1826 BCC and 796 SCC), compared with never use, frequent (at least weekly) NSAID use was associated with reduced risk of BCC (HR 0·84, 95% confidence interval 0·71-0.99) but not SCC. Aspirin use was associated with reduced risk of SCC (HR 0·77, 95% confidence interval 0·64-0·93) only among infrequent (less than weekly) users and was not associated with BCC. We observed no association between NSAID or aspirin use and the risk of BCC or SCC among average-to-low-risk participants. CONCLUSIONS: While some weakly inverse associations were observed between prior use of aspirin or NSAIDs and skin cancer, the inconsistent patterns of associations do not provide convincing evidence that these medications reduce subsequent skin cancer risk. Further data on doses, duration and long-term follow-up may help us to comprehend the cumulative dose effect.

Do airline pilots and cabin crew have raised risks of melanoma and other skin cancers? Systematic review and meta-analysis.

BACKGROUND: Airline pilots and cabin crew are potentially exposed to hazardous ultraviolet and cosmic radiation, which may increase their risk of melanoma and other skin cancers. OBJECTIVES: To establish precise risks of melanoma and keratinocyte cancer (KC) for airline pilots and for cabin crew based on all studies published to date. METHODS: We searched MEDLINE, ISI Science Citation Index, Embase, SCOPUS and CINAHL to June 2018. All studies of melanoma and KC risk and mortality in airline pilots and cabin crew compared with the general population were eligible. Standardized incidence ratios (SIRs) and standardized mortality ratios (SMRs) were pooled using random effects models. RESULTS: From 5866 papers retrieved, we reviewed 44 full-text articles, of which 12 studies with data collected mostly between the 1970s and 1990s were eligible for inclusion. The pooled SIR (pSIR) for melanoma in pilots was 2.03 [95% confidence interval (CI) 1.71-2.40] and in cabin crew it was 2.12 (95% CI 1.71-2.62). For pilots, the pooled SMR for melanoma was 1.99 (95% CI 1.17-3.40) and for cabin crew it was 1.18 (95% CI 0.73-1.89). For KC, the pSIR was 1.86 (95% CI 1.54-2.25) in pilots and 1.97 (95% CI 1.25-2.96) in cabin crew. There was no evidence of study heterogeneity. CONCLUSIONS: The available evidence shows that airline pilots and cabin crew have about twice the risk of melanoma and other skin cancers than the general population, with pilots more likely to die from melanoma. However, most of the evidence was collected several decades ago and their relevance to contemporary levels of risk is uncertain.

How many melanomas might be prevented if more people applied sunscreen regularly?

BACKGROUND: Ultraviolet radiation causes cutaneous melanoma. Sunscreen prevents sunburn and protects skin cells against mutations. High-quality epidemiological studies suggest regular sunscreen use prevents melanoma. OBJECTIVES: To calculate the potential impact fraction (PIF) for melanoma in the U.S.A. and Australia assuming a range of different intervention scenarios intended to increase sunscreen use. METHODS: We calculated the PIF, the proportional difference between the observed number of melanomas arising under prevailing levels of sunscreen use compared with the number expected under counterfactual scenarios. We used published melanoma incidence projections for Australia and the white population in the U.S.A. from 2012 through to 2031 as the baseline condition, with estimates for protective effects of 'regular sunscreen use' from the literature. Sunscreen prevalence was sourced from national or state surveys. RESULTS: Under a plausible public health intervention scenario comprising incremental increases in sunscreen prevalence over a 10-year implementation programme, we estimated that cumulatively to 2031, 231 053 fewer melanomas would arise in the U.S. white population (PIF 11%) and 28 071 fewer melanomas would arise in Australia (PIF 10%). Under the theoretical maximum model of sunscreen use, almost 797 000 (PIF 38%) and approximately 96 000 (PIF 34%) melanomas would be prevented in the U.S.A. and Australia, respectively between 2012 and 2031. A sensitivity analysis using weaker effect estimates resulted in more conservative PIF estimates. CONCLUSIONS: Overall, interventions to increase use of sunscreen would result in moderate reductions in melanoma incidence, assuming no compensatory overexposure to the sun. Countries with a high incidence of melanoma should monitor levels of sunscreen use in the community.

Cutaneous squamous cell carcinoma: an epidemiological review.

Cutaneous squamous cell carcinoma (SCC) is a common cancer in white populations and its disease burden is often substantially underestimated. SCC occurs more often in men than women and increases dramatically with age; those affected often develop multiple primaries over time, which increases the burden. The main external cause is solar ultraviolet radiation (UVR), with immunosuppression being the other established risk factor, shown by the high SCC rates in organ transplant recipients. Sunbed use and certain genetic disorders and medical conditions are also associated with SCC, while associations with human papillomavirus infection and high bodyweight are not established. The presence of actinic keratoses (AKs) on sun-damaged skin is one of the strongest predictors of SCC in unaffected people and a very small proportion of AKs are SCC precursors, although the true rate of malignant transformation of AKs is unknown. The mainstay of SCC prevention is protection of the skin from undue sun exposure by use of clothing cover and sunscreen during summer or in sunny places. Educational, behavioural and multicomponent interventions directed at individuals ranging from parents of newborns, to school children and adolescents, to outdoor workers, have repeatedly been shown to be effective in improving sun-protective behaviours. Health policies can facilitate SCC prevention by setting standards for relevant behaviours to reduce UVR exposure, for example, by legislated restriction of the tanning industry. Skin cancer prevention initiatives are generally highly cost-effective and public investment should be encouraged to control the growing public health problems caused by SCC.

Azathioprine and Risk of Skin Cancer in Organ Transplant Recipients: Systematic Review and Meta-Analysis.

Azathioprine, a purine antimetabolite immunosuppressant, photosensitizes the skin and causes the production of mutagenic reactive oxygen species. It is postulated to increase the risk of squamous cell carcinoma (SCC) and other skin cancers in organ transplant recipients (OTRs), but evidence from multiple, largely single-center studies to date has been inconsistent. We aimed to resolve the issue of azathioprine's carcinogenicity by conducting a systematic review of the relevant literature and pooling published risk estimates to evaluate the risks of SCC, basal cell carcinoma (BCC), keratinocyte cancers (KCs) overall and other skin cancers in relation to azathioprine treatment. Twenty-seven studies were included in total, with risk estimates from 13 of these studies able to be pooled for quantitative analysis. The overall summary estimate showed a significantly increased risk of SCC in relation to azathioprine exposure (1.56, 95% confidence interval [CI] 1.11-2.18). No significant associations between azathioprine treatment and BCC (0.96, 95% CI 0.66-1.40) or KC (0.84, 95% CI 0.59-1.21) risk were observed. There was significant heterogeneity between studies for azathioprine risk estimates and the outcomes of SCC, BCC and KC. The pooled findings of available evidence support the contention that treatment with azathioprine increases the risk of SCC in OTRs.