Estimating personal solar ultraviolet radiation exposure through time spent outdoors, ambient levels and modelling approaches.

BACKGROUND: Evidence on validation of surrogates applied to evaluate the personal exposure levels of solar ultraviolet radiation (UVR) in epidemiological studies is scarce. OBJECTIVES: To determine and compare the validity of three approaches, including (i) ambient UVR levels, (ii) time spent outdoors and (iii) a modelling approach integrating the aforementioned parameters, to estimate personal UVR exposure over a period of 6 months among indoor and outdoor workers and in different seasons (summer/winter). METHODS: This validation study was part of the European Commission-funded ICEPURE project and was performed between July 2010 and January 2011 in a convenience sample of indoor and outdoor workers in Catalunya, Spain. We developed linear regression models to quantify the variation in the objectively measured personal UVR exposure that could be explained, separately, by the ambient UVR, time spent outdoors and modelled UVR levels. RESULTS: Our 39 participants - mostly male and with a median age of 35 years - presented a median daily objectively measured UVR of 0·37 standard erythemal doses. The UVR dose was statistically significantly higher in summer and for outdoor workers. The modelled personal UVR exposure and self-reported time spent outdoors could reasonably predict the variation in the objectively measured personal UVR levels (R2 range 0·75-0·79), whereas ambient UVR was a poor predictor (R2 = 0·21). No notable differences were found between seasons or occupation. CONCLUSIONS: Time outdoors and our modelling approach were reliable predictors and of value to be applied in epidemiological studies of the health effects of current exposure to UVR.

Sunscreen claims, risk management and consumer confidence.

This essay is a personal reflection on how the concept of risk is impacting on the development of sunscreen products and claims, and whether these developments are jeopardizing consumer confidence. In order to estimate the risk of harm, we need not only to identify a hazard but, as importantly, determine the degree of exposure to the hazard and understand the health of impact of consequent exposure. A practice by many manufacturers is simply to market a product that claims to be protective against a hazard with little, or no, regard to exposure or consequence. The inherent danger with this approach is to undermine trust in product efficacy and in so doing to put at risk consumer confidence in both product and manufacturer. An example of this approach using infrared radiation as the hazard will be discussed.

Cet essai est une réflexion personnelle sur la façon dont le concept de risque influe sur le développement de produits solaires adaptés et leurs allégations, et si ces développements compromettent la confiance des consommateurs. Afin d'estimer le risque de préjudice, nous avons besoin non seulement d'identifier un risque mais, et c'est tout aussi important, de déterminer le degré de l'exposition au risque et de comprendre l'impact sur la santé d'une exposition conséquente. La pratique de nombreux fabricants consiste simplement à commercialiser un produit qui prétend avoir un effet protecteur contre un danger, avec peu ou aucun égard vis-à-vis de l'exposition ou des conséquences. Le risque inhérent à cette approche est de compromettre la confiance dans l'efficacité des produits et ce faisant, de mettre en péril la confiance des consommateurs envers les produits et les fabricants. Un exemple de cette approche utilisant les rayons infrarouges comme risque fera l'objet de la discussion.

A theoretical and experimental study of the temporal reduction in UV protection provided by a facial day cream.

OBJECTIVE: To investigate how the UV protection provided by a facial day cream reduces over the course of a day. METHODS: We developed a theoretical model using a Monte Carlo random sampling approach to estimate the variation in local thickness, and hence local effective SPF, at several different sites over the face. The input variables, which are labelled SPF, average application thickness, homogeneity of the product on the skin and the ability of the product to bind to the skin, allow examination of how these different factors affect the delivered photoprotection. We compared the results of our modelling with experimental determination of the binding of an oil-in-water moisturizing day cream with a rated SPF of 15 at various times over the course of a day by means of UV photography and digital image analysis. RESULTS: We demonstrated good agreement between our theoretical predictions of the temporal reduction in product thickness and the experimental observations. We used our modelling approach to show that a substantial reduction in lifetime UV burden on the face could be achieved by a daycare product delivering 3-fold (or greater) protection over the face. CONCLUSION: Comparison with experimental data confirmed the robustness and validity of our model, which predicts that products intended for daily use need to be formulated carefully and applied uniformly, and to have a half-life of binding to the skin of several hours. Products that bind less well to the skin, or are applied non-uniformly, are likely to be providing inadequate protection with regards to influencing the rate of photoaging of the skin. Our data suggest that after a single, realistic application of a day cream rated SPF15, consumers' faces remain protected to at least an average of 5-fold around the middle of the day, especially pertinent to indoor workers who are likely to be exposed to maximum UV levels as they venture outside during their lunch break.

The perplexing dilemma of measuring sun protection factors.

Truth, like knowledge, is surprisingly difficult to define. Indeed, every definition of truth that philosophers have developed falls prey to the question, 'Is it true?' In this essay, we consider what is the true SPF of a sunscreen product and whether it can ever be realizable.

The influence of HIV infection on the age dependence of squamous cell carcinoma of the skin in South Africa.

BACKGROUND: Cancer incidence typically increases with age, but it is not known whether ethnic characteristics influence the age dependence of squamous cell carcinoma of the skin (SCC). OBJECTIVES: (i) To determine the age dependence of SCC in the black African, coloured and white population groups of South Africa (SA); and (ii) to show whether any differences in the rate of change of age dependence could be influenced by diversity in behaviour and lifestyle, especially with regard to the prevalence of HIV infection, rather than by a fundamental variation in cancer biology between the populations. METHODS: Linear regression analysis was applied to the logarithm of the age-specific incidence rates for SCC v. the logarithm of age between 35 and 74 years. The slopes of the regression (age exponent) were compared for each subset of gender, population group and year of diagnosis (between 2000 and 2010). RESULTS: The most notable feature was the low value of the age exponent in both male and female black African compared with the white and coloured populations. This finding could be explained in part by the difference in the prevalence of HIV infection in the black African population group compared with the white and coloured population groups. CONCLUSIONS: The prevalence of HIV infection in black Africans in SA tends to decrease the apparent age component in SCC compared with the white and coloured population groups. Other factors relating to lifestyle and behaviour that differ between the population groups are also likely to influence the age component in SCC.

Optimizing the spectral absorption profile of sunscreens.

OBJECTIVE: To investigate whether sunscreens provide optimal protection by exhibiting a uniform spectral absorption profile throughout the ultraviolet spectrum or by having a spectral profile in which absorption in the UVB waveband is greater than in the UVA region. METHODS: A sunscreen with a flat spectral absorption profile was compared with one of the same SPF in which the SPF to UVA protection was in the ratio of 3 : 1 in terms of protecting against erythema and chronic effects with different action spectra, as well as the total UV burden to the skin. RESULTS: A sunscreen with spectral profile in which absorption in the UVB waveband is greater than in the UVA region confers no benefit in terms of erythema (and endpoints with similar action spectra) than a sunscreen with the same SPF that exhibits uniform absorption at all wavelengths throughout the UV spectrum. More importantly, the '3 : 1 profile' offers inferior protection when endpoints with other action spectra are considered, as well as resulting in a total UV burden to the skin that is about 5 times higher than sunscreen products showing a flat spectral absorption profile. CONCLUSION: It may be tempting to believe that it is beneficial to increase the absorption of sunscreens in the UVB region relative to the UVA to reflect the fact that skin damage is associated more with UVB than UVA exposure. However, this belief is a fallacy and consumers are best served with sunscreens in which the spectral protection profile is uniform at all wavelengths throughout the UV spectrum.

The influence of HIV infection on the age dependence of squamous cell carcinoma of the skin in South Africa

Background. Cancer incidence typically increases with age, but it is not known whether ethnic characteristics influence the age dependence of squamous cell carcinoma of the skin (SCC).Objectives. (i) To determine the age dependence of SCC in the black African, coloured and white population groups of South Africa (SA); and (ii) to show whether any differences in the rate of change of age dependence could be influenced by diversity in behaviour and lifestyle, especially with regard to the prevalence of HIV infection, rather than by a fundamental variation in cancer biology between the populations.Methods. Linear regression analysis was applied to the logarithm of the age-specific incidence rates for SCC v. the logarithm of age between 35 and 74 years. The slopes of the regression (age exponent) were compared for each subset of gender, population group and year of diagnosis (between 2000 and 2010).Results. The most notable feature was the low value of the age exponent in both male and female black African compared with the white and coloured populations. This finding could be explained in part by the difference in the prevalence of HIV infection in the black African population group compared with the white and coloured population groups.Conclusions. The prevalence of HIV infection in black Africans in SA tends to decrease the apparent age component in SCC compared with the white and coloured population groups. Other factors relating to lifestyle and behaviour that differ between the population groups are also likely to influence the age component in SCC

A novel proposal for labelling sunscreens based on compliance and performance.

OBJECTIVE: To propose a new way of classifying sunscreens, which combines the labelled SPF with an objective measure of compliance. METHODS: The in vitro determination of uniformity of sunscreen application was combined with an in vivo measure of applied thickness to derive a Compliance Factor for each of 10 sunscreens. RESULTS: The predicted SPF resulting from real-life application of each sunscreen product, which is termed the SPF(in vivo veritas), was calculated from the Compliance Factor and the labelled SPF. It was shown that for a number of products, there is expected to be a significant mismatch between labelled and delivered SPF. CONCLUSION: We believe that by adopting our proposal, consumers would be given more appropriate guidance on the delivered photoprotection they can expect to receive than relying solely on the labelled SPF.

The risk of squamous cell carcinoma in women from exposure to UVA lamps used in cosmetic nail treatment.

BACKGROUND: The use of ultraviolet (UV)A lamps for curing gel nails is widespread in the cosmetic nail industry. A report that two women who had undergone this treatment subsequently developed squamous cell carcinoma (SCC) on the dorsum of hands has prompted some concern about the safety of this procedure. OBJECTIVES: To estimate the number of women who would need to be exposed to UVA nail lamps for one woman to develop SCC on the dorsum of hands, who would not have done so otherwise. METHODS: A mathematical model that combines age and UV exposure was used to compare the risk of developing SCC due to typical sun exposure with the risk of inducing these cancers from exposure to UVA nail lamps. RESULTS: For typical usage, the analysis indicates that tens or hundreds of thousands of women would need to use a UVA nail lamp regularly for one to go on to develop SCC on the dorsum of the hands as a direct consequence. CONCLUSIONS: The risk of inducing an SCC from exposure to UVA nail lamps is very low and one that is likely to be accepted by most women. Even then, the risk can be reduced to virtually zero by wearing fingerless gloves when the hands are being exposed.

Predicting the efficacy of sunscreens in vivo veritas.

A novel in vitro technique for measuring the efficacy of sunscreens over the skin surface is described. It is demonstrated that those products that spread easily are associated with both a low variance in delivered SPF and a subjective assessment of a product that is pleasing to use, which in turn results in a higher application thicknesses and greater delivered photoprotection leading to improved health benefits of sunscreen use.

An overview analysis of the time people spend outdoors.

BACKGROUND: An important factor in determining our exposure to sunlight, and the consequent impact on skin health and vitamin D status, is the time we spend outdoors. OBJECTIVES: To determine estimates of the typical times per day spent outdoors during weekdays, weekends and holidays during a summer season. METHODS: A number of published studies giving data on the time per day spent outdoors by people were reviewed and a meta-analysis performed. From these data summary estimates of the average time per day outdoors were extracted. RESULTS: Time spent per day outdoors during weekdays and weekends is positively skewed, with a normal distribution of times outdoors during holidays. The median times per day outdoors during weekdays and weekends gave pooled estimates of 1·04 and 1·64 h, respectively. Corresponding values for the pooled estimates of mean times outdoors during these two periods were 1·43 and 2·38 h. The mean time per day outdoors during holiday exposure is 5-6 h. CONCLUSIONS: Summer-long distribution of times spent outdoors on a daily basis exhibits a highly skewed nature that highlights the difference between our adventitious and recreational exposure. Over the course of a summer season, when people are outside, they spend on average of 1-2 h per day outdoors.

Modelling the seasonal variation of vitamin D due to sun exposure.

BACKGROUND: The current interest in vitamin D as a preventive agent in many chronic diseases has led to a reappraisal of adequate sun exposure. Yet just what constitutes adequacy remains to be clearly defined and validated. To do this requires an understanding of how behaviour outdoors during the year translates into seasonal changes in vitamin D status. OBJECTIVES: To develop a model for estimating the changes in serum 25-hydroxyvitamin D [25(OH)D] levels as a consequence of sun exposure throughout the year. METHODS: A novel mathematical model is described that incorporates the changes in serum 25(OH)D following a single, whole-body exposure to solar ultraviolet radiation with daily sun exposure in order to estimate the annual variation in serum 25(OH)D. RESULTS: The model yields results that agree closely with measured data from a large population-based study. Application of the model showed that current advice about 10-20 min of daily sun exposure during the summer months does little in the way of boosting overall 25(OH)D levels, while sufficient sun exposure that could achieve a worthwhile benefit would compromise skin health. CONCLUSIONS: There is little in the way of public health advice concerning the benefits of sun exposure that can be given as an effective means of maintaining adequate vitamin D levels throughout the year. Instead it would seem safer and more effective to fortify more foods with vitamin D and/or to consider the use of supplements during the winter months. Messages concerning sun exposure should remain focused on the detrimental effects of excessive sun exposure and should avoid giving specific advice on what might be 'optimal' sun exposure.

Sunscreens as a preventative measure in melanoma: an evidence-based approach or the precautionary principle?

BACKGROUND: Meta-analyses of observational case-control studies have demonstrated no association between sunscreen use and the development of malignant melanoma. OBJECTIVES: To postulate whether modern sunscreens are likely to be effective as a preventative agent in melanoma and, if so, how many cases might be avoided by their use. METHODS: The potential number of melanomas prevented by encouraging the use of modern, high SPF, broad spectrum sunscreens during recreational summer exposure was estimated by combining the prevalence of their use with the relative risk of melanoma in nonusers compared with those people who regularly use these products. RESULTS: Notwithstanding the inherent uncertainties and assumptions that this approach involves, it is shown that significant numbers of melanomas might be avoided by regular sunscreen use during recreational summer sun exposure, and with them appreciable financial, social and emotional costs, even for very modest estimates of the benefit of broad-spectrum sunscreens. CONCLUSIONS: Despite the lack of evidence demonstrating the efficacy of modern sunscreens in preventing melanoma, it is argued that it would be irresponsible not to encourage their use, along with other sun protection strategies, as a means of combating the year-on-year rise in melanoma incidence.

Reported sun exposure, attitudes to sun protection and perceptions of skin cancer risk: a survey of visitors to Cancer Research UK's SunSmart campaign website.

BACKGROUND: Skin cancer is the most commonly diagnosed cancer in the U.K. With the aim of reducing, and hopefully reversing, the year-on-year rise in skin cancer incidence, SunSmart, the U.K.'s national skin cancer prevention campaign, has been hosted by Cancer Research UK since 2003. OBJECTIVES: To gather data about how much time visitors to the SunSmart website spend in the sun, their preferred forms of sun protection and their use of tools such as sun-reactive skin type and ultraviolet (UV) index. METHODS: The study was carried out using a quantitative on-line survey hosted by Cancer Research UK's SunSmart website (http://www.sunsmart.org.uk) between May and September 2007. RESULTS: Just over 2000 respondents completed the survey. Young adults are more likely to experience sunburn than older adults, a factor that was found to be much more important than individual susceptibility to sunburn. Initiatives such as using the UV index to guide sun exposure and checking skin regularly for unusual changes both appeared to be associated with a lower incidence of recent sunburn. The distribution of time spent outdoors by indoor workers during summer months demonstrated clearly how important recreational exposure is in influencing the overall solar UV burden. CONCLUSIONS: This on-line survey, while not entirely representative of the U.K. population, has highlighted those factors that can be effective in reducing the incidence of sunburn, and presumably skin cancer, and that messages about the secondary prevention of skin cancer clearly have some overlap with those advocating primary prevention.