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 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

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.

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.

NFAT regulates induction of COX-2 and apoptosis of keratinocytes in response to ultraviolet radiation exposure.

The nuclear factor of activated T cells (NFAT) transcription factors are regulated by calcium/calcineurin signals and play important roles in T cells, muscle, bone, and neural tissue. NFAT is expressed in the epidermis, and although recent data suggest that NFAT is involved in the skin's responses to ultraviolet radiation (UVR), the wavelengths of radiation that activate NFAT and the biological function of UV-activated NFAT remain undefined. We demonstrate that NFAT transcriptional activity is preferentially induced by UVB wavelengths in keratinocytes. The derived action spectrum for NFAT activation indicates that NFAT transcriptional activity is inversely associated with wavelength. UVR also evoked NFAT2 nuclear translocation in a parallel wavelength-dependent fashion and both transcriptional activation and nuclear translocation were inhibited by the calcineurin inhibitor cyclosporin A. UVR also evoked NFAT2 nuclear translocation in three-dimensional skin equivalents. Evidence suggests that COX-2 contributes to UV-induced carcinogenesis. Inhibiting UV-induced NFAT activation in keratinocytes, reduced COX-2 protein induction, and increased UV-induced apoptosis. COX-2 luciferase reporters lacking functional NFAT binding sites were less responsive to UVR, highlighting that NFAT is required for UV-induced COX-2 induction. Taken together, these data suggest that the proinflammatory, antiapoptotic, and procarcinogenic functions of UV-activated COX-2 may be mediated, in part, by upstream NFAT signaling.

The challenge of follow-up in narrowband ultraviolet B phototherapy.

BACKGROUND: The use of narrowband ultraviolet (UV) B phototherapy to treat psoriasis and other disorders has increased markedly since the TL-01 lamps were introduced in the 1980s. While broadband UVB phototherapy has generally been considered to be a relatively safe treatment, some concern has been raised about the potential increased skin cancer risk with narrowband UVB. OBJECTIVES: The likelihood of a patient who is free of nonmelanoma skin cancer (NMSC) at the start of phototherapy developing a malignancy after a certain follow-up period will be dependent not only on the carcinogenic potential of the treatment but also on the age-conditional probability of natural occurrence. We were interested to explore the potential difficulty of designing studies to separate these two events. Methods Mathematical models were developed that combined age-conditional probabilities of developing NMSC due to natural causes with the risk of inducing these cancers from narrowband UVB phototherapy in order to estimate the excess number of cancers resulting from this therapeutic intervention in a cohort of patients. RESULTS: Within-department studies will be most unlikely to demonstrate that the number of NMSCs observed in follow-up studies is significantly different from that expected in an untreated population, even for a follow-up period of 20 years. CONCLUSIONS: Determination of the carcinogenic potential associated with narrowband UVB will require large multicentre studies typically involving several thousand new patients per year and followed up for 10 years or more.

Sunscreens and melanoma: the future looks bright.

BACKGROUND: Meta-analyses of observational case-control studies have demonstrated no association between sunscreen use and the development of malignant melanoma. OBJECTIVES: To examine whether this observation is to be expected given the period during which the case-control studies were conducted, the sunscreens prevalent at that time, and how sunscreen is used and applied in practice. To predict whether modern sunscreens are likely to be effective as a preventative agent in melanoma. METHODS: The protection against solar ultraviolet radiation delivered by sunscreens available prior to the early 1990s (when the data used in most published case-control studies were collected) was estimated by combining their absorption properties with the amount applied in a way reflecting common usage. Similar estimates were made for the protection offered by modern sunscreens. RESULTS: It is not surprising that case-control studies have failed to find any association between sunscreen use and the risk of melanoma when consideration is given to the sunscreens in common usage at the time and the way in which sunscreen is applied in practice. Modern high Sun Protection Factor, broad-spectrum sunscreens, on the other hand, can be expected to be an effective measure in helping to prevent melanoma compared with sunscreens typical of those used 10-20 years ago. CONCLUSIONS: It is reasonable to suppose that the improvement in performance of modern sunscreens will lead to a worthwhile benefit as a preventative agent against melanoma, although these benefits may not be seen for several decades.

The future incidence of cutaneous melanoma within the UK.

BACKGROUND: The incidence of cutaneous malignant melanoma continues to rise in the U.K., where since the 1970s malignant melanoma has seen the largest increase in incidence rates compared with other major cancers. To counteract this rise, sun awareness campaigns have been introduced in this and several other countries since the 1980s with the object of encouraging people to limit their exposure to strong sunshine and to avoid sunburn in the expectation that these interventions will act favourably on skin cancer incidence. OBJECTIVES: To predict the incidence of cutaneous malignant melanoma in the British population over the next half-century as a consequence of either a stabilization or a reduction in lifetime risk of melanoma for recent and future birth cohorts so that cancer services can be planned appropriately over the coming years. METHODS: An age-cohort model has been developed that estimates future incidence rates of melanoma in the U.K. RESULTS: The results suggest that the benefits of intervention strategies, assuming that these will translate eventually into a downturn in melanoma incidence, may not be seen for another 30 years or so, by which time the predicted age-standardized rate of melanoma may be around twice that presently observed. CONCLUSIONS: Prevention of deaths from melanoma depends on both reducing incidence and achieving earlier diagnosis. This analysis has indicated that the former is unlikely to be realized in the U.K. for some decades, and so early detection of suspected lesions, with prompt surgery to remove confirmed tumours, is paramount if mortality from melanoma is to be kept in check.

Implication for photosensitive patients of ultraviolet A exposure in vehicles.

BACKGROUND: Photosensitive patients sometimes report disease flares during journeys by car. Window glass blocks all UVB but not all UVA. All car windscreens are made from laminated glass. Side and rear windows are usually made of nonlaminated glass. OBJECTIVES: To determine which types of glass provide most protection from UVA with particular reference to the implications for patients with polymorphic light eruption (PLE). METHODS: The percentage transmission of UVA was determined for a selection of glass, both laminated and nonlaminated, and with differing colour tints. RESULTS: Laminated glass transmits less UVA than nonlaminated glass. Tinted glass transmits less UVA than clear glass. Nonlaminated clear glass transmitted the highest percentage of UVA (62.8%) and grey laminated glass the lowest (0.9%). A dose of 5 J cm(-2) UVA, enough to trigger PLE in some patients, could be transmitted through clear nonlaminated glass in 30 min but would take 50 h through grey laminated glass. CONCLUSION: Patients with severe UVA-induced PLE and other photosensitivity disorders may have disease flares from solar UVA transmission through side-window glass. Protective measures such as wearing long-sleeved clothing, keeping the arm beneath the bottom of the window aperture, or choosing tinted and laminated car windows may be helpful.

A quantitative estimate of melanoma mortality from ultraviolet A sunbed use in the U.K.

BACKGROUND: Concern has been expressed for many years in the medical and regulatory literature about the adverse health effects, especially melanoma, from the use of sunbeds for cosmetic tanning. OBJECTIVES: To estimate the mortality from melanoma as a result of the use of sunbeds for cosmetic tanning in the U.K. METHODS: A model using a Monte Carlo random sampling technique was developed to estimate human ultraviolet exposure to both sunlight and sunbeds, and these data were used to predict the contribution of sunbeds to melanoma mortality in the U.K. RESULTS: The mortality from melanoma due to sunbed use each year in the U.K. is estimated to be about 100 deaths. CONCLUSIONS: Sunbed use could be regarded as a relatively minor self-imposed detriment to public health compared with other voluntary 'pleasurable' activities associated with significant mortality, such as smoking and drinking alcohol. While cosmetic tanning using sunbeds should be discouraged, prohibition is not warranted especially as exposure to the sun, which cannot be regulated, remains the major contributory factor to the risk of melanoma.