When should sunscreen be applied: The balance between health benefit and adverse consequences to humans and the environment.

Objective: To propose a strategy for using sunscreens that optimizes the balance between skin health and adverse effects to humans and the environment.

Methods: A model was developed to explore the relationship between sunscreen usage and personal sun exposure throughout the year in populations resident at different latitudes.

Results: There is little biological justification in terms of skin health for applying sunscreen over the 4-6 winter months at latitudes of 45° N and higher, whereas year-round sunscreen is advised at latitudes of 30° N and lower.

Is sunscreen alone effective at preventing sunburn on a high-solar beach vacation: A modeling study?

Beach holidays in areas of strong sunlight are popular and sunscreen is often the primary means of photoprotection favored by many people. The object of this study was to estimate how effective sunscreen is in preventing sunburn under high ultraviolet (UV) levels. We used a computational model to determine how the quantity, frequency, substantivity, and labeled SPF of applied sunscreens impact on the predicted erythemal response in unacclimatized skin over the course of a 7-day holiday in a high-solar environment.

Natural and Simulated Solar Radiation.

The extra-terrestrial solar spectrum corresponds approximately to a black body of temperature about 5,800 K, with the ultraviolet region accounting for almost 8% of the total solar energy. Terrestrial solar spectral irradiance peaks at around 500 nm in the blue-green region, whereas the diffuse component peaks in the UVAI-blue region of the spectrum, with the infrared component comprising almost entirely direct radiation. Several factors impact on the magnitude and spectral profile of terrestrial solar spectral irradiance, and these include solar elevation, reflection from land and sea, air pollution, altitude above sea level and cloud cover.

Sunscreen and the Precautionary Principle.

The Precautionary Principle is a decision-making device designed to help us when we deal with uncertain risks. Despite a number of case-control and prospective studies over several years, there remains some uncertainty as to whether sunscreens are unequivocally effective in reducing the risk of skin cancer, and we examine how useful the principle is in deciding whether sunscreen should be included in the sun protection toolbox as a public health measure. We conclude that the Precautionary Principle can be a useful tool supporting public health recommendations to use sunscreen as a means of reducing the morbidity and mortality of skin cancer, but we show that it is not without its shortcomings.

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.

Erythema and Acclimatization Following Repeated Sun Exposure: A Modeling Study.

The development of a computational model is described that allows time-varying erythema and acclimatization to be determined following repeated exposure to solar ultraviolet (UV) radiation. Good agreement was observed between experimental data and model predictions. Results are presented that illustrate how daily, adventitious sun exposure over the course of a year can result in occasional erythema generally in the late spring/early summer, while at the same time showing how the photoadaptive response of the skin changes throughout the year at different latitudes and for different sun-reactive skin types.

Correction: A library of action spectra for erythema and pigmentation.

Correction for 'A library of action spectra for erythema and pigmentation' by Alois W. Schmalwieser et al., Photochem.

Drivers for Sun Protection in Black South Africans.

Sun protection behavior studies are almost exclusively carried out in populations with fair skin for the obvious reason that people with unpigmented skin are more susceptible to the health impacts of excess solar ultraviolet radiation exposure. In a dataset of 1271 Black South Africans, we analyzed factors related to sun protection applied when spending time outdoors including awareness of skin cancer, gender, age and Living Standards Measure (LSM) where 1-4 equate to the lowest, 5-7 intermediate and 8-10 the highest LSM status. The most important driver for Black South Africans to use sun protection was whether they were aware of skin cancer (OR: 2.

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 Impact of Sunlight on Adventitious Buying and Giving.

The impact of sunlight on the income derived from spending and donations in a coastal charitable facility is examined. Data consisted of income during 2017 and 2018, together with daily sunshine hours and apparent temperature, and a multiple linear regression model was employed to determine the importance of these meteorological variables on income. Results indicated that income increased with both increasing sunshine hours and apparent temperature, but with an interaction effect (negative coefficient) between sunlight and apparent temperature such that the effect of sunlight on income is positive at lower apparent temperatures and negative at higher apparent temperatures.

Sunburn and sun protection in black skin.

Background: People with black skin are much less susceptible to sunburn than white-skinned individuals, yet there are scarce data on self-reported incidence of sunburn and sun protection measures in people with deeply-pigmented skin.

Method: An on-line survey tool was used to collect self-assessed data about demographic variables, sunburn incidence, and use of sun protection modalities.

Results: Two-thirds of respondents with black skin living in the UK claimed never to have been sunburnt; a much higher proportion than those living in South Africa and Nigeria where 34 and 46%, respectively, reported never experiencing sunburn.

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.

Time and Place as Modifiers of Personal UV Exposure.

It is a common belief that, if we want to limit our sun exposure during outdoor recreational activities and holidays in order to avoid sunburn or reduce our risk of skin cancer, we need to reach for the bottle of sunscreen or cover up with clothing. As important as these measures are, there is another way to enjoy our time outdoors and still benefit from the experience. In this article, we consider the impact of time, place, and behaviour outdoors on our exposure to solar ultraviolet (UV) radiation.

Sunburn at the seaside.

Background/purpose: The purpose of this paper is to estimate the contribution to our erythemal exposure at the coast of solar ultraviolet (UV) both reflected from, and transmitted into, the ocean.

Methods: The reflection of solar UV radiation from, and transmitted into, seawater was calculated using a numerical model under a number of atmospheric conditions to estimate erythemal exposure on the skin of supine/prone and ambulant people.

Results: The results were expressed as UV Indices.

Melanin distribution in human epidermis affords localized protection against DNA photodamage and concurs with skin cancer incidence difference in extreme phototypes.

Epidermal DNA damage, especially to the basal layer, is an established cause of keratinocyte cancers (KCs). Large differences in KC incidence (20- to 60-fold) between white and black populations are largely attributable to epidermal melanin photoprotection in the latter. The cyclobutane pyrimidine dimer (CPD) is the most mutagenic DNA photolesion; however, most studies suggest that melanin photoprotection against CPD is modest and cannot explain the considerable skin color-based differences in KC incidence.

The Solar Ultraviolet Environment at the Ocean.

Atmospheric and oceanic radiative transfer models were used to compute spectral radiances between 285 and 400 nm onto horizontal and vertical plane surfaces over water. The calculations kept track of the contributions by the sun's direct beam, by diffuse-sky radiance, by radiance reflected from the sea surface and by water-leaving radiance. Clear, hazy and cloudy sky conditions were simulated for a range of solar zenith angles, wind speeds and atmospheric ozone concentrations.

Ultraviolet erythema: dose response and mediator diffusion.

The earliest contribution made by Jan van der Leun to the field of photobiology was studying the mechanism of UV-induced erythema in human skin - a subject he chose for his PhD in the 1960s. His contribution to this topic encouraged us to continue this work and over a number of years in the 1980s and 1990s, we carried out several studies on quantitative aspects of UV erythema. A major part of Jan's thesis focused on diffusion processes in UV erythema and his observations led him to conclude that erythema induced by radiation with wavelengths of around 300 nm was due to the actions of a diffusing mediator arising in the epidermis, whereas radiation at shorter wavelengths around 254 nm, caused erythema by exerting a direct effect on the dermal blood vessels.

Labelled sunscreen SPFs may overestimate protection in natural sunlight.

Limited evidence exists to indicate that sunscreen protection factors determined in the laboratory are higher than those in natural sunlight. In this article we propose an explanation for this difference and estimate the expected SPFs of sunscreen products in natural sunlight and those expected from laboratory testing. Our results indicate that the labelled SPF, determined by in vivo assay using a UV solar simulator, overestimates the SPF that would be expected in natural sunlight to the extent that for products labelled SPF50+, it may not be possible to achieve a protection against sunlight of more than 25-fold.

Age-specific acceleration in malignant melanoma.

The overall incidence of melanoma has increased steadily for several years. The relative change in incidence at different ages has not been fully described.  To describe how incidence at different ages has changed over time and to consider what aspects of tumour biology may explain the observed pattern of change in incidence.

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.

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.