British Journal of DermatologyEarly View Perspectives Is it necessary to wear sunscreen indoors? Brian L. Diffey, Corresponding Author Brian L. Diffey brian.diffey@ncl.ac.uk orcid.org/0000-0002-8955-125X Translational and Clinical Research Institute (Dermatology), Newcastle University, Newcastle upon Tyne, NE2 4HH UKEmail: brian.diffey@ncl.ac.ukContribution: Conceptualization (lead), Formal analysis (lead), Methodology (lead), Software (lead), Writing - original draft (lead), Writing - review & editing (lead)Search for more papers by this author Brian L. Diffey, Corresponding Author Brian L. Diffey brian.diffey@ncl.ac.uk orcid.org/0000-0002-8955-125X Translational and Clinical Research Institute (Dermatology), Newcastle University, Newcastle upon Tyne, NE2 4HH UKEmail: brian.diffey@ncl.ac.ukContribution: Conceptualization (lead), Formal analysis (lead), Methodology (lead), Software (lead), Writing - original draft (lead), Writing - review & editing (lead)Search for more papers by this author First published: 23 August 2022 https://doi.org/10.1111/bjd.21850 Conflicts of interest: the authors declare they have no conflicts of interest. Data availability statement: data available on request from the author. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Early ViewOnline Version of Record before inclusion in an issue RelatedInformation

In the early 1970s, environmental conservationists were becoming concerned that a reduction in the thickness of the atmospheric ozone layer would lead to increased levels of ultraviolet (UV) radiation at ground level, resulting in higher population exposure to UV and subsequent harm, especially a rise in skin cancer. At the time, no measurements had been reported on the normal levels of solar UV radiation which populations received in their usual environment, so this lack of data, coupled with increasing concerns about the impact to human health, led to the development of simple devices that monitored personal UV exposure. The first and most widely used UV dosimeter was the polymer film, polysulphone, and this review describes its properties and some of the pioneering studies using the dosimeter that led to a quantitative understanding of human exposure to sunlight in a variety of behavioral, occupational, and geographical settings.

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. The radiances were used to estimate erythemal exposures due to the sun and sky, as well as from radiation reflected by the sea surface and backscattered from the water column. Diffuse-sky irradiance is usually greater than direct-sun irradiance at wavelengths below 330 nm, and reflected and water-leaving irradiance accounts for <20% of the UV exposure on a vertical surface. Total exposure depends strongly on solar zenith angle and azimuth angle relative to the sun. Sea surface roughness affects the UV exposures by only a few percent. For very clear waters and the sun high in the sky, the UV index within the water can be >10 at depths down to two meters and >6 down to 5 m.

SummaryBackground/purposeThe 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.MethodsThe 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.ResultsThe results were expressed as UV Indices. Even under the most extreme insolation with the sun directly overhead, where the ambient UV Index may be around 14, reflected UV from the ocean contributes an erythemal exposure to the skin equivalent to a UV Index of about 0.7. For typical ocean waters, with the sun high in the sky, the UV index within the water is about 7 at a depth of 2 m.ConclusionWhilst our eyes often sense a high level of reflected sunlight from the ocean, especially when the sun is low in the sky, our skin does not share that experience. The reason people get sunburnt at the seaside has more to do with the absence of shade than with reflectance by the water surface or even beach sand.

On days during the summer months when high temperatures are expected, weather forecasters frequently warn about the dangers of UV and high UV indices. It is not surprising, therefore, that it is a common belief that high ambient air temperatures are a major risk factor for burning. Although the UV index is generally higher on cloudless, hot days compared with cloudy, cool days, reliance should not be placed on ambient temperature alone as a guide to the need for sun protection. This article is protected by copyright. All rights reserved.

Biological responses of human skin to UVR including cancer and aging are largely wavelength-dependent, as shown by the action spectra of UVR-induced erythema and nuclear DNA (nDNA) damage. A molecular dosimeter of UVR exposure is therefore required. Although mitochondrial DNA (mtDNA) damage has been shown to be a reliable and sensitive biomarker of UVR exposure in human skin, its wavelength dependency is unknown. The current study solves this problem by determining the action spectrum of UVR-induced mtDNA damage in human skin. Human neonatal dermal fibroblasts and primary human adult keratinocyte cells were irradiated with increasing doses of UVR. Dose-response curves of mtDNA damage were produced for each of the UVR sources and cell types, and an action spectrum for each cell type was determined by mathematical induction. Similarities between these mtDNA damage action spectra and previously determined nDNA damage were observed, with the most detrimental effects occurring over the shorter UVR wavelengths. Notably, a statistically significant (P<0.0001) greater sensitivity to mtDNA damage was observed in dermal fibroblasts compared with keratinocytes at wavelengths >300 nm, possibly indicating a wider picture of depth dependence in sensitivity. This finding has implications for disease/photodamage mechanisms and interventions.

SummaryBackground/PurposeAcquiring a tanned skin, either by sunbathing, sunbed use, or a combination of both, is a desirable objective for many people. The objective here was to compare the ultraviolet (UV) exposure resulting from a 2‐week vacation spent sunbathing with sunscreen‐protected skin, with that from a typical course of 10 sessions on a sunbed.MethodsA numerical analysis combining data on sunlight and sunbed UV levels, time spent tanning and spectral absorption properties of different types of sunscreen.ResultsThe analysis showed that unless a sunscreen provides optimal broad‐spectrum protection, a 2‐week sunbathing vacation that avoids sunburn on sunscreen‐protected skin can result in a higher cumulative UV exposure than a typical 10‐session sunbed course. The lowest exposures for a given sun protection factor (SPF) are obtained when sunscreen delivers broad‐spectrum protection that approaches the ideal of uniform absorption at all wavelengths throughout the UV spectrum.ConclusionIn extreme cases of recreational sun exposure where sunscreens providing suboptimal broad‐spectrum protection are used, the UV insult to the skin is likely to result in higher cumulative exposures than commonly employed sunbed practices.

The advent of the social desirability of a tanned skin is generally attributed to Coco Chanel who, on returning from holiday on the French Riviera, proclaimed ‘The 1929 girl must be tanned’. For the next 50 years a uniform, tanned skin could only be achieved by sunbathing but in the 1970s, the sunbed industry was born following the development of high‐intensity ultraviolet (UV) A fluorescent lamps, the same lamps that allowed psoralen plus UVA (PUVA) therapy to be established. In the period subsequent to the late 1970s, there have been several reports on the demographics of sunbed use. A study in the BJD1 confirms a common feature of sunbed users, which has been present in all demographic studies ever since the first study of sunbed users in the U.K. appeared in this journal in 1986,2 that is, that young females are the predominant group who engage in cosmetic tanning. However, a worrying feature of the German study1 was the finding that age at initiation of sunbed use decreased significantly across birth cohorts from 25 to 19 years (25th percentile; cohorts 1966–75 to 1986–93).

Journal Article Seeing is believing Get access B. Diffey B. Diffey Dermatological Sciences Institute of Cellular Medicine University of Newcastle Newcastle upon Tyne U.K Search for other works by this author on: Oxford Academic Google Scholar British Journal of Dermatology, Volume 169, Issue 2, 1 August 2013, Page 240, https://doi.org/10.1111/bjd.12407 Published: 01 August 2013

A mathematical model is described for estimating changes in plasma 25-hydroxyvitamin D (25(OH)D) levels throughout the year as a consequence of varying the oral intake of vitamin D and the behaviour outdoors of white British adults resident in different regions of the UK. The model yields seasonal and geographical patterns of 25(OH)D concentrations that agree closely with observational studies. Use of the model allows estimates to be easily made of the sun exposure and oral intake necessary to avoid vitamin D deficiency in defined proportions of the population, as well as strategies that would lead to vitamin D sufficiency throughout the year. The analysis demonstrates that addressing concerns about insufficient vitamin D levels, especially during the winter, may be achieved by modifying oral vitamin D intake over the winter, increasing summer sun exposure or a combination of both.

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.

Two articles, both from Scandinavia, published in this issue of the Journal and the July issue compare the relative effectiveness of narrowband (311 nm) ultraviolet (UV) radiation and oral vitamin D on increasing serum concentration of 25hydroxyvitamin D [25(OH)D]. The Swedish article specifically targeted subjects with vitamin D deficiency [defined as 25(OH)D < 25 nmol L], while the paper from Finland was concerned with healthy subjects whose 25(OH)D levels were < 75 nmol L. The findings from each of these studies were very similar in that 12–18 full body narrowband UVB exposures given over 4–6 weeks were more efficient in treating both vitamin D deficiency and improving the vitamin D status of healthy subjects in winter than prescription of a daily oral intake of vitamin D 20–40 lg. It has become fashionable to regard a serum 25(OH)D concentration < 75 nmol L as ‘insufficient’ and that concentrations of 75–150 nmol L are recommended for health. However, this recommendation is not universal; others have argued that serum 25(OH)D concentrations between 50 and 75 nmol L are adequate for good health and that the term ‘vitamin D insufficiency’ should be limited to serum concentrations between 25 and 50 nmol L. Certainly, it would be appropriate to regard serum levels between 50 and 75 nmol L as ‘normal’ as they reflect typical concentrations of those observed in studies of 25(OH)D status in British people where the mean serum 25(OH)D averaged over the year ranged from 52 to 58 nmol L. So should we be advocating a course of UV exposure during the winter months to people living in more northerly latitudes, including the U.K.? The Finnish authors conclude that the results from their study support the use of narrowband UVB as an effective and safe way to improve vitamin D balance in healthy subjects in winter. They maintain that the UVB doses used in their study were smaller than those used when treating psoriasis and the mean cumulative dose of 48Æ4 standard erythema dose (SED) is comparable to that received during a sunny day in the summer. While the former statement is true, they fail to recognize that a dose of 48Æ4 SED is around the maximum clear-sky ambient UV received during a full summer day in Europe. Personal exposures are considerably less than this, typically < 2 SED during a summer day. Furthermore, a dose of 48Æ4 SED is about one-third of the annual solar UV exposure of indoor workers in northern Europe and so their assertion that this is a ‘safe’ dose is open to debate. More importantly, it is controversial as to whether someone exhibiting a ‘normal’ 25(OH)D concentration should be subjected to a medical intervention. From a pragmatic viewpoint, access to UVB phototherapy cabins in dermatology departments would be grossly inadequate to treat the large proportion of apparently healthy members of the population whose serum 25(OH)D levels were < 75 nmol L. This lack of resource would be seized upon by the cosmetic tanning industry who would welcome the opportunity to fill the unmet ‘need’. Two years ago the chairman of the Sunbed Association, a trade organization representing sunbed operators, manufacturers and distributors of sunbeds in the U.K., wrote ‘A few minutes 2–3 times a week on a sunbed has long been known and recommended by international experts as a viable way of securing and maintaining adequate vitamin D levels’. This claim is not without substance as peer-reviewed studies have demonstrated that sunbeds designed for cosmetic tanning, which emit almost entirely UVA radiation, can be effective in raising serum 25(OH)D levels as a result of the small amount of UVB (typically around 1% of the UV emission) present in the lamp spectrum. Yet addressing vitamin D status is a medical problem and patients exhibiting vitamin D deficiency deserve the best therapy combining high efficacy with minimal risk. Options include systemic medication or phototherapy with UVB (and not UVA) radiation as was demonstrated in the study by Bogh et al. What should not happen is for the results from the Finnish study to be interpreted by the ‘worried well’ as a licence to seek out UV exposure and for the cosmetic tanning industry to exploit this dubious need.

Journal Article Why dermatologists shouldn’t practise in red light districts Get access B.L. Diffey B.L. Diffey Dermatological Sciences, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K. E‐mail: brian.diffey@ncl.ac.uk Search for other works by this author on: Oxford Academic Google Scholar British Journal of Dermatology, Volume 165, Issue 4, 1 October 2011, Page 925, https://doi.org/10.1111/j.1365-2133.2011.10484.x Published: 01 October 2011

BACKGROUND:Exposure to solar ultraviolet (UV) radiation is believed to be an important contributor to facial photoaging. Daily application of topical photoprotectants is thought to mitigate this process.OBJECTIVES:To examine the importance of a number of independent factors in reducing the lifetime UV exposure of facial skin achieved by daily use of photoprotective products.METHODS:A behavioral model of solar UV exposure to the face is incorporated with the spectral profile of two different candidate topical products, the age at which regular photoprotection begins, the SPF of the products, and whether the product is applied year-round or just in the summer months to examine the reduction in lifetime UV exposures achieved by daily use of photoprotective products.RESULTS:The results show that regular use of topical photoprotective agents reduces significantly lifetime UV exposure to the face compared with nonuse. Analysis of variance shows that the most important factor is to begin regular daily use early in life. The SPF and spectral profile of the product is of lesser importance, as is whether daily use is confined to the summer months rather than year-round.CONCLUSIONS:While it remains unproven and speculative, there is good reason to suppose that regular use of daily facial topical products containing UV filters, particularly if started early in adult life, will be translated into fewer visible signs of aging later in life.

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.

Conflicts of interest None declared. It is a profound and necessary truth that the deep things in science are not found because they are useful; they are found because it was possible to find them.– Robert Oppenheimer Melanoma and vitamin D synthesis are the two impacts of cutaneous sun exposure that provoke the greatest concern, debate and controversy and these are brought together in a study reported in this issue by researchers from Copenhagen.1 In a small study they showed that following a diagnosis of melanoma, patients changed their habits to receive lower sun exposure than before diagnosis, using changes in serum 25‐hydroxyvitamin D [25(OH)D] and skin pigmentation before and after diagnosis as proxy measures of ultraviolet (UV) exposure. Furthermore, they showed that winter levels of 25(OH)D immediately following diagnosis were higher than in a control group or in patients diagnosed up to 6 years previously and inferred from this that in the summer leading up to diagnosis, sun exposure was especially high.