Impact of Artificial UV Light Sources on the Skin

  • Patrick Joseph Tierney

    Student thesis: Doctoral ThesisDoctor of Philosophy


    UV radiation has the ability to cause erythema, photoaging and photo-cancer. In 2010 Westminster wanted information on sources of artificial UV radiation in particular sunbeds. The objective of this study was to measure the spectral outputs from artifcial tanning units throughout England and to compare the outputs to European and British compliance levels. The emissions from the collated data allowed the calculation of exposure doses of each sunbed. By applying plausible sunbed exposure habits (no of sunbed sessions per year) it was possible to use this data in a skin cancer mathematical model. The time-dose model is based on cumulative lifetime exposure dose and age. The first step was to apply plausible sunbed habit scenarios using the collated emission
    data which was used in a mathematical model to estimate the risk of developing non-melanoma skin cancer. Another objective of this study was to determine the optical properties of skin tissue that govern the transport of light through tissue and secondly to develop a model for light transport in tissue that makes it possible to investigate the number
    of photons absorbed beneath the skin. Different skin types of various pigmentation levels were investigated. To this end, the absorption and scattering properties of tissue as a function of wavelength were derived. The effect of photo-lesion formation from DNA damage was investigated. To study light transport in tissue, a Monte Carlo model has was
    developed. This model gives a full 3-D simulation of light transport, and takes into account specular reflection and refraction at the tissue boundaries. To validate the model, predictions have been tested against reliable analytical data. Monte Carlo simulations are implemented to investigate the propagation of UV photons in skin tissue. In this thesis, a data driven semi-empirical model is presented that used spec-
    tra obtained from sunbed emissions in the Monte Carlo Radiative Transfer (MCRT) code. A number of applications of the model, together with results from experiments are presented such as skin type photo-shielding and quantification of DNA damage. UV radiation can affect the appearance and the sensitivity of human skin by triggering a biophysical response such as eythema (redness). A pilot study is presented that investigates if multiple sub-erythemal doses can induce erythema in the skin. The study involved healthy volunteers and photosensitive patients. It is demonstrated that the multiple sub-erythemal doses have an additive mechanism.
    Date of Award2015
    Original languageEnglish
    SponsorsCancer Research UK
    SupervisorHarry Moseley (Supervisor)

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