Skin Color Analysis of Various Body Parts (Forearm, Upper Arm, Elbow, Knee, and Shin) and Changes with Age in 53 Korean Women, Considering Intrinsic and Extrinsic Factors

Background/Objectives: Skin color is innately determined by race and other genetic factors, and it also undergoes acquired changes due to various intrinsic and extrinsic factors. Previous studies on skin color have mainly focused on the face, and research has recently expanded to other body parts. However, there is limited information about the age-dependent changes in the skin color of these body parts. The purpose of this study is to analyze the differences in skin color between various body parts and the changes in skin color of each body part with age. Methods: This study examined the skin color of 53 Korean women subjects evenly distributed in age from the 20s to 60s on several body parts: forearm, upper arm, elbow (extended or folded), knee (extended or folded), thigh, and shin. The lightness (L*), redness (a*), and yellowness (b*) were measured using a spectrophotometer, and the individual typology angle (ITA°) was calculated from the L* and b* values. The melanin index and erythema index were measured using the mexameter. Results: The results showed that the elbow skin had the lowest L* and ITA° values and the highest a* and b* values among the examined body parts, followed by the knee. The melanin index and erythema index were also high in the skin of these body parts. In the analysis of age-dependent changes in the skin color of various body parts, the forearm skin exhibited the most notable decrease in the L* and ITA° values and increases in the a* and b* values, followed by upper-arm skin. The melanin and erythema indices in the forearm also increased as the subjects aged, whereas those in the elbow and knee rather decreased with age. Conclusions: This study suggests that differences in intrinsic and extrinsic skin aging in various body parts may be expressed as different changes in skin color and raises the need for cosmetic and dermatological research to identify the physiological significance of these changes.

Post-Translational Modifications Evoked by Reactive Carbonyl Species in Ultraviolet-A-Exposed Skin: Implication in Fibroblast Senescence and Skin Photoaging

Photoaging is an accelerated form of aging resulting from skin exposure to ultraviolet (UV) radiation. UV-A radiation deeply penetrates the dermis and triggers the generation of reactive oxygen species (ROS) which promotes damage to DNA, lipids and proteins. Lipid peroxidation results from the oxidative attack of polyunsaturated fatty acids which generate a huge amount of lipid peroxidation products, among them reactive carbonyl species (RCS) such as α, β-unsaturated hydroxyalkenals (e.g., 4-hydroxynonenal), acrolein or malondialdehyde. These highly reactive agents form adducts on free NH2 groups and thiol residues on amino acids in proteins and can also modify DNA and phospholipids. The accumulation of RCS-adducts leads to carbonyl stress characterized by progressive cellular and tissular dysfunction, inflammation and toxicity. RCS-adducts are formed in the dermis of skin exposed to UV-A radiation. Several RCS targets have been identified in the dermis, such as collagen and elastin in the extracellular matrix, whose modification could contribute to actinic elastosis lesions. RCS-adducts may play a role in fibroblast senescence via the modification of histones, and the sirtuin SIRT1, leading to an accumulation of acetylated proteins. The cytoskeleton protein vimentin is modified by RCS, which could impair fibroblast motility. A better identification of protein modification and carbonyl stress in the dermis may help to develop new treatment approaches for preventing photoaging.

Combined Toxicological Effects of Di (2-Ethylhexyl) Phthalate and UV-B Irradiation through Endoplasmic Reticulum Stress-Tight Junction Disruption in Human HaCaT Keratinocytes

Di (2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer, and human exposure to DEHP is widespread and frequent. However, information about the combined effect of DEHP and ultraviolet (UV)-B on the skin are still limited. We investigated the cytotoxic effects of DEHP and UV-B on HaCaT keratinocytes and evaluated the related underlying mechanisms involving endoplasmic reticulum (ER) stress signals and the disruption of junction complexes as an effective target for skin inflammation. Our results revealed that co-treatment with DEHP and UV-B irradiation alleviated the cell cytotoxicity and markedly decreased X-box binding protein 1 (XBP1), endoplasmic reticulum oxidoreductase 1 alpha (Ero1α), and C/EBP homologous protein (CHOP) whereas a single dose of 40 mJ/cm² UV-B generated mild ER stress to slightly less or similar levels as that seen with DEHP. DEHP was also shown to inhibit tight junctions (TJs) after UV-B irradiation, increased apoptosis by altering apoptotic gene Bax and stress kinases, JNK, and p38 MAPK. Furthermore, exposure of HaCaT cells to DEHP and UV-B irradiation resulted in the marked suppression of the nuclear factor kappa B (NF-κB)/p65 signaling pathway. Taken together, our data suggest that nontoxic DEHP and UV-B irradiation regulated ER stress and epidermal TJ disruption with the induction of apoptosis activation and the secretion of proinflammatory cytokines such as interleukin 1 beta (IL-1β) and IL-6 in human keratinocytes. Further investigation is needed to confirm the mechanisms implicated in its toxicity and determine the effects of exposure to DEHP and UV-B irradiation on markers involved in this study.

Possibilities to estimate the personal UV radiation exposure from ambient UV radiation measurements

People are exposed to solar ultraviolet radiation (UVR) throughout their entire lives. Exposure to UVR is vital but also poses serious risks. The quantification of human UVR exposure is a complex issue. Personal UVR exposure is related to ambient UVR as well as to a variety of factors such as the orientation of the exposed anatomical site with respect to the sun and the duration of exposure. This is mainly determined by personal behaviour. A variety of efforts have been made in the past to measure or model the personal UVR exposure of people and often personal UVR exposure has been expressed as the percentage of ambient UVR. On the other hand, ambient UVR is being monitored at a variety of places and measurements are available even online. This suggests that both the knowledge of personal UVR exposure and measurements of ambient UVR is required. In this paper, a summary on the different methods, which use ambient UVR measurements to estimate personal UVR exposure of people, as well as a few examples, are given. Advantages and disadvantages will be discussed as well as possibilities and limitations. This also includes an overview of appropriate terminology, units and basic statistic parameters to describe personal UVR exposure.

Solar Ultraviolet Radiation Risk Estimates-A Comparison of Different Action Spectra and Detector Responsivities

Studies assessing the dose–response relationship for human skin cancer induction by solar ultraviolet radiation (UVR) apply a range of methods to quantify relevant UVR doses, but information about the comparability of these datasets is scarce. We compared biologically weighted effectivities applying the most relevant UVR action spectra in order to test the ability of certain UVR detectors to mimic these biological effects at different times during the day and year. Our calculations were based on solar spectra measured at Dortmund, Germany (51.5° N) and at Townsville, Australia (19.3° S), or computed for latitudes 20° S and 50° N. Convolutions with the CIE action spectra for erythema and non-melanoma skin cancer (NMSC) and with ICNIRP’s weighting function showed comparable solar zenith angle (SZA) dependences with little influence of season or latitude. A different SZA dependence was found with Setlow’s action spectrum for melanoma induction. Calculations for a number of UVR detector responsivities gave widely discrepant absolute irradiances and doses, which were nevertheless related to those calculated with both CIE spectra by correction factors largely independent of the SZA. Commonly used detectors can thus provide quite accurate estimates of NMSC induction by solar UVR, whereas they may be inadequate to mimic melanoma induction.

Sun exposure to the eyes: predicted UV protection effectiveness of various sunglasses

The aim of this study was to assess solar ultraviolet radiation (UVR) doses received by the eyes in different exposure situations, and to predict the sun protection effectiveness provided by various styles of sunglasses at facial, periorbital, and ocular skin zones including the cornea and accounting for different head positions. A 3D numeric model was optimized to predict direct, diffuse and reflected erythemally weighted UVR doses received at various skin zones. Precisely defined facial, periorbital, and ocular skin zones, sunglasses (goggles, medium-, and large-sized sunglasses) and three head positions were modeled to simulate daily (08:00-17:00) and midday (12:00-14:00) UVR doses. The shading from sunglasses' frame and lenses' UVR transmission were used to calculate a predictive protection factor (PPF [%]). Highest ocular daily UVR doses were estimated at the uncovered cornea (1718.4 J/m²). Least sun protection was provided by middle-sized sunglasses with highest midday dose at the white lateral (290.8 J/m²) and lateral periorbital zones (390.9 J/m²). Goggles reached almost 100% protection at all skin zones. Large-sized sunglasses were highly effective in winter; however, their effectiveness depended on diffuse UVR doses received. In "looking-up" head positions highest midday UVR doses were received at the unprotected cornea (908.1 J/m²), totally protected when large-sized sunglasses are used. All tested sunglass lenses fully blocked UVR. Sunglasses' protection effectiveness is strongly influenced by geometry, wearing position, head positions, and exposure conditions. Sunglasses do not totally block UVR and should be combined with additional protection means. 3D modeling allows estimating UVR exposure of highly sensitive small skin zones, chronically exposed and rarely assessed.

Personal electronic UVR dosimeter measurements: specific and general uncertainties

Personal ultraviolet radiation (UVR) dosimetry has been performed for decades to objectively measure human exposure to UVR. These measurements have been used to investigate solar behaviour and its negative effects on human health such as skin cancer and positive effects such as vitamin D formation. A specific electronic dosimeter is described with a spectral sensitivity as the erythema response for human skin and temperature measurements for compliance control. Technical, methodological and environmental causes of uncertainties regarding personal UV dosimetry are investigated using this dosimeter as an example, which enables us to show the dosimeter's limitations and enables readers to compare their dosimeters with that described and to increase awareness of imperfections of dosimeters. The dosimeter's spectral response, cosine response, linearity, temperature dependency and sensitivity are investigated. As opposed to biological and chemical dosimeters, electronic dosimeters do not measure UV radiation continuously but at time-intervals (sampling). The error introduced by sampling is investigated for sampling intervals from 1 second up to 60 seconds for 3 groups of people (n = 18, 1.1-4.6 hours of positive UV measurements) on sunny (n = 12) and cloudy (n = 6) days. Increasing the sample time by 1 second added on average an uncertainty of maximum +0.29% to -0.27% per added second compared to the 1-second sample time. The importance of dirt on the sensor was investigated in 24 dosimeters after 6 months use by farmers. The reduction in the registered dose due to the dirty sensor was 2.3% (median = 2.0%, inter-quartile range = 2.0%, max = 5%) suggesting that dirt on the sensor generally does not play a significant role.

Facial exposure to ultraviolet radiation: Predicted sun protection effectiveness of various hat styles

BACKGROUND/PURPOSE

Solar ultraviolet radiation (UVR) doses received by individuals are highly influenced by behavioural and environmental factors. This study aimed at quantifying hats' sun protection effectiveness in various exposure conditions, by predicting UVR exposure doses and their anatomical distributions.

METHODS

A well-defined 3-dimensional head morphology and 4 hat styles (a cap, a helmet, a middle- and a wide-brimmed hat) were added to a previously published model. Midday (12:00-14:00) and daily (08:00-17:00) seasonal UVR doses were estimated at various facial skin zones, with and without hat wear, accounting for each UVR component. Protection effectiveness was calculated by the relative reduction in predicted UVR dose, expressed as a predictive protection factor (PPF).

RESULTS

The unprotected entire face received 2.5 times higher UVR doses during a summer midday compared to a winter midday (3.3 vs 1.3 standard erythema dose [SED]) with highest doses received at the nose (6.1 SED). During a cloudless summer day, the lowest mean UVR dose is received by the entire face protected by a wide-brimmed hat (1.7 SED). No hat reached 100% protection at any facial skin zone (PPF_max : 76%). Hats' sun protection effectiveness varied highly with environmental conditions and was mainly limited by the high contribution of diffuse UVR, irrespective of hat style. Larger brim sizes afforded greater facial protection than smaller brim sizes except around midday when the sun position is high.

CONCLUSION

Consideration of diffuse and reflected UVR in sun educational messages could improve sun protection effectiveness.

Efficiency of ocular UV protection by clear lenses

Ocular UV doses accumulate all-day, not only during periods of direct sun exposure. The UV protection efficiency of three clear lenses was evaluated experimentally, validated by simulation, and compared to non-UV protection: a first spectacle lens with a tailored UV absorber, a second spectacle lens, minimizing UV back reflections, as well as a third spectacle lens, combining both. A tailored UV-absorber efficiently reduced overall UV irradiance to 7 %, whereas reduction of back-reflections still left UV irradiance at 42 %. Thus, clear lenses with a tailored UV absorber efficiently protect the eye from UV, supplementing sun glasses wear to an all-day protection scenario.

Distributions of Direct, Reflected, and Diffuse Irradiance for Ocular UV Exposure at Different Solar Elevation Angles

To analyze intensities of ocular exposure to direct (E_o,dir), reflected (E_o,refl), and diffuse (E_o,diff) ultraviolet (UV) irradiance at different solar elevation angles (SEAs), a rotating manikin and dual-detector spectrometer were used to monitor the intensity of ocular exposure to UV irradiation (E_o) and ambient UV radiation (UVR) under clear skies in Sanya, China. E_o,dir was derived as the difference between maximum and minimum measured E_o values. E_o,refl was converted from the value measured at a height of 160 cm. E_o,diff was calculated as the minimum measured E_o value minus E_o,refl. Regression curves were fitted to determine distributions of intensities and growth rates at different wavelengths and SEAs. E_o,dir differed from ambient UVR exposure. Linear, quadratic, and linear E_o,dir distributions were obtained in SEA ranges of 14°–30°, 30°–50°, and 50°–90°, respectively, with maximum E_o,dir at 32°–38° SEA. Growth rates of E_o,dir with increasing wavelength were fitted with quadratic functions in all SEA ranges. Distributions and growth rate of E_o,refl values were fitted with quadratic functions. Maximum E_o,diff was achieved at the same SEA for all fitted quadratic functions. Growth rate of E_o,diff with increasing wavelength was fitted with a linear function. E_o,dir distributions were fitted with linear or quadratic functions in different SEA ranges. All E_o,refl and E_o,diff distributions were fitted with quadratic functions. As SEA increased, the E_o,dir portion of E_o increased and then decreased; the E_o,refl portion increased from an initial minimum; and the E_o,diff portion first decreased and then increased. The findings may provide data supporting on construction of a mathematical model of ocular UV exposure.

The angular distributions of ultraviolet spectral irradiance at different solar elevation angles under clear sky conditions

To investigate the angular distributions of UVA, UVB, and effective UV for erythema and vitamin D (vitD) synthesis, the UV spectral irradiances were measured at ten inclined angles (from 0° to 90°) and seven azimuths (from 0° to 180°) at solar elevation angle (SEA) that ranged from 18.8° to 80° in Shanghai (31.22° N, 121.55° E) under clear sky and the albedo of ground was 0.1. The results demonstrated that in the mean azimuths and with the back to the sun, the UVA, UVB, and erythemally and vitD-weighted irradiances increased with the inclined angles and an increase in SEA. When facing toward the sun at 0°-60° inclined angles, the UVA first increased and then decreased with an increase in SEA; at other inclined angles, the UVA increased with SEA. At 0°-40° inclined angles, the UVB and erythemally and vitD-weighted irradiances first increased and then decreased with an increase in SEA, and their maximums were achieved at SEA 68.7°; at other inclined angles, the above three irradiances increased with an increase in SEA. The maximum UVA, UVB, and erythemally and vitD-weighted irradiances were achieved at an 80° inclined angle at SEA 80° (the highest in our measurements); the cumulative exposure of the half day achieved the maximum at a 60° inclined angle, but not on the horizontal. This study provides support for the assessment of human skin sun exposure.

The consequences for human health of stratospheric ozone depletion in association with other environmental factors

Ozone depletion, climate and human health.

Ozone depletion and climate change: impacts on UV radiation

Percentage changes in the UV Index (UVI) for 2090 relative to 2015 due to changes in ozone (left) and aerosols (right) only. Large decreases are projected over Antarctica due to stratospheric ozone recovery. Increases are projected for parts of Asia due to decreases in aerosols, partly reversing the possible large reductions in UVI after the 1950s.

A novel method to calculate solar UV exposure relevant to vitamin D production in humans

We present a novel method to calculate vitamin D3 -weighted exposure by integrating the incident solar spectral radiance over all relevant parts of the human body. Earlier investigations are based on the irradiance on surfaces, whereas our calculated exposure of a voxel model of a human takes into account the complex geometry of the radiation field. Assuming that sufficient vitamin D3 (1000 international units) can be produced within the human body in one minute for a completely uncovered body in vertical posture in summer at midlatitudes (e.g. Rome, June 21, noon, UV index of 10), we calculate the exposure times needed in other situations or seasons to gain enough vitamin D3 . Our calculations show that the UV index is not a good indicator for the exposure which depends on the orientation of the body (e.g. vertical (standing) or horizontal (lying down) posture). Without clothing the exposure is dominated by diffuse sky radiation and it is nearly irrelevant how the body in vertical posture is oriented toward the sun. At the winter solstice (December 21, noon, cloudy) at least in central Europe sufficient vitamin D3 cannot be obtained with realistic clothing, even if the exposure were extended to all daylight hours.