Human UVA exposures estimated from ambient UVA measurements

Dynamic visualization of ultraviolet dose on skin with sunscreen applied using minimum erythema dose

BACKGROUND

Visualizing the ultraviolet (UV) dose on skin serve as an intuitive approach to ensure appropriate sunscreen usage and reduce the risk of erythema. UV dose is determined by a number of external factors, such as properties of sunscreens, weather, and type of outdoor activity. We propose a framework for visualizing UV doses that considers various external factors.

MATERIALS AND METHODS

First, the skin of a three-dimensional human model was represented using triangular meshes, and various static postures and dynamic motions were simulated to express outdoor activities. Then, we evaluated the persistency and insufficiency properties of sunscreen, which are time dependent and directly affect the effectiveness of the sunscreen skin protection factor (SPF) during UV exposure. Finally, to calculate the UV dose in real time, we tracked the trajectory of the sun and motion of the skin while considering the time-dependent properties of sunscreen.

RESULTS

An S/W system was implemented based on the proposed framework to visualize the distribution of UV doses through dynamic color changes in exposed skin areas. The color types include true colors, which represent the minimum erythema dose (MED), and pseudo colors representing states before 1 MED is reached. We devised various examples to discuss the usability of the proposed framework.

CONCLUSION

The system conveniently displays the MED according to an individual's skin phototype. When the properties of a wide range of commercial sunscreens are added to the system database, it is expected that the rate of appropriate sunscreen usage by customers will increase.

Wireless, battery-free, flexible, miniaturized dosimeters monitor exposure to solar radiation and to light for phototherapy

Exposure to electromagnetic radiation can have a profound impact on human health. Ultraviolet (UV) radiation from the sun causes skin cancer. Blue light affects the body's circadian melatonin rhythm. At the same time, electromagnetic radiation in controlled quantities has beneficial use. UV light treats various inflammatory skin conditions, and blue light phototherapy is the standard of care for neonatal jaundice. Although quantitative measurements of exposure in these contexts are important, current systems have limited applicability outside of laboratories because of an unfavorable set of factors in bulk, weight, cost, and accuracy. We present optical metrology approaches, optoelectronic designs, and wireless modes of operation that serve as the basis for miniature, low-cost, and battery-free devices for precise dosimetry at multiple wavelengths. These platforms use a system on a chip with near-field communication functionality, a radio frequency antenna, photodiodes, supercapacitors, and a transistor to exploit a continuous accumulation mechanism for measurement. Experimental and computational studies of the individual components, the collective systems, and the performance parameters highlight the operating principles and design considerations. Evaluations on human participants monitored solar UV exposure during outdoor activities, captured instantaneous and cumulative exposure during blue light phototherapy in neonatal intensive care units, and tracked light illumination for seasonal affective disorder phototherapy. Versatile applications of this dosimetry platform provide means for consumers and medical providers to modulate light exposure across the electromagnetic spectrum in a way that can both reduce risks in the context of excessive exposure and optimize benefits in the context of phototherapy.

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.

A numeric model to simulate solar individual ultraviolet exposure

Exposure to solar ultraviolet (UV) light is the main causative factor for skin cancer. UV exposure depends on environmental and individual factors. Individual exposure data remain scarce and development of alternative assessment methods is greatly needed. We developed a model simulating human exposure to solar UV. The model predicts the dose and distribution of UV exposure received on the basis of ground irradiation and morphological data. Standard 3D computer graphics techniques were adapted to develop a rendering engine that estimates the solar exposure of a virtual manikin depicted as a triangle mesh surface. The amount of solar energy received by each triangle was calculated, taking into account reflected, direct and diffuse radiation, and shading from other body parts. Dosimetric measurements (n = 54) were conducted in field conditions using a foam manikin as surrogate for an exposed individual. Dosimetric results were compared to the model predictions. The model predicted exposure to solar UV adequately. The symmetric mean absolute percentage error was 13%. Half of the predictions were within 17% range of the measurements. This model provides a tool to assess outdoor occupational and recreational UV exposures, without necessitating time-consuming individual dosimetry, with numerous potential uses in skin cancer prevention and research.

Reintroduction of a classic vitamin D ultraviolet source

As early as 1930 sunlamps claiming to provide ultraviolet (UV) exposure to make vitamin D were sold to the public in the US and Canada for home use. Today even with dietary supplementation of vitamin D many people do not get enough solar UV exposure to maintain sufficient vitamin D levels. There is growing interest in the availability of sunlamps for this purpose. The original Sperti Sunlamp, with label claiming vitamin D benefit was approved by the American Medical Association in 1940 as a sunlamp. This intermediate pressure mercury lamps ultraviolet B emission lines, at 297, 302, and 313 nm are able to convert 7-dehydrocholesterol in the skin to vitamin pre-D3 initiating the natural process of vitamin D formation. Today's KBD Vitamin D lamp, an updated model of the earlier type source. In order to comply with modern safety guidance, the source is filtered to remove unnecessary UVC radiation and is equipped with a timer to control the dose administered. The 5 min timer provides an exposure, at 20 in. from the user's skin, of one standard erythemal dose (SED). The SED represents a suberythemal dose for even the most sensitive skin type I individual.

Peripheral light focusing as a potential mechanism for phakic dysphotopsia and lens phototoxicity

Our aim was to examine secondary image formation in the anterior segment caused by peripheral light focusing (PLF) in the human cornea, and in particular the crystalline lens. Non-sequential ray-tracing (OptiCAD) was applied to an anatomically based human eye model, which incorporates a gradient index crystalline lens. For analysis of the limbal effect, we varied the incident angle from 100 to 122 degrees, while for the crystalline lens effect, the incident angle was varied from 60 to 90 degrees. The corneal shapes studied included central radii from 7.4 to 8.2 mm with a range of shape factors. In each case, we computed the peak and average intensities, and the area of exposure at the limbus or lens periphery. The computation was repeated with a previous model eye for comparison. For the limbal effect, a peak intensity gain of x22.5 was found at an incident angle of 104 degrees which compares well with previous results. The average intensity gain at this angle was x7.5 over an area of 0.23 mm2. Steeper corneal curvature produced a greater PLF effect. For the crystalline lens effect, maximum UVA (365 nm) intensity gain peaked at x8.6 at 84 degrees with average intensity gain of x2.3. The area of UVA exposure peaked at 4.7 mm2 at 70 degrees. A relatively wide range (30 degrees ) of incident angles produced peak PLF gains of x3 or more in the lens. Significant focusing of light is directed to the nasal limbus, and to a lesser extent to the crystalline lens over a broad range of incident angles. PLF in the nasal cornea is reduced by an order of magnitude when a UV-blocking soft contact lens is used. The concentration levels and intraocular sites of PLF action on UV and visible light suggest a new mechanism of phakic dysphotopsia and lens phototoxicity.