Protecting Workers from Ultraviolet Radiation - icnirp

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Protecting Workers from Ultraviolet Radiation Skin appendages are pilosebaceous follicles, eccrine sweat glands and aprocrine sweat glands. They are exceptionally affected by UVR damages. In adults, nerve endings are located immediately under the epidermis and are responsible for the pain following UVR-induced effects. 3.2.2 Acute effects on the skin 3.2.2.1 Sunburn “Sunburn” is an acute injury following excessive exposure to UVR and is most pronounced for lightly pigmented skin types. Sunburn is actually not caused by heat or caustic chemicals, but is the result of a phototoxic (actinic) effect in the skin. Unlike the other burns, sunburn is not immediate. Skin redness reaches a maximum at about 8-12 hours after exposure and fades within a few days. The red appearance of the skin (erythema) results from an increased blood content near the skin’s surface. The non-adapted (“untanned”) skin of very lightly pigmented Caucasian subjects will normally show signs of a mild reddening after about 4 hours following only a half-hour exposure to midday summer sunshine in mid-latitudes. Higher doses may result in pain and skin swelling (edema) with blistering, and after a few days, peeling. Sunburn sensitivity varies substantially with skin complexion and color, and this is reflected in the solar exposure time required to induce a sunburn reaction--from 15-30 minutes of midday summer sunshine to 1-2 hours exposure for moderately pigmented skin; and those with darkly pigmented skin may not clearly show a sunburn for a full day exposure. Skin specialists frequently group individuals into one of six sun-reactive skin types (Table 1), and these skin types fall into three more significant groups based upon how well individuals produce the pigment, melanin, in their skin (see next section) (Joint ISO/CIE 1999/1998, Fitzpatrick TB et al 1995, Diffey 1994, Parrish et al 1982). Specialized measurement quantities are useful when describing sunburn sensitivity. A person’s Minimum Erythemal Dose (MED) is defined as the UVR exposure that will produce a just perceptible erythema 8-24 hours after irradiation of the skin. It is very important to recognize that the MED is specific to one individual and it varies with the source of UVR the tanning capacity and any adaptation from previous exposures. Because the MED measure refers only to an individual, there exists a related, standardized quantity for source measurement: the Standard Erythemal Dose unit (SED) to quantify the ability of a source to produce erythema. This unit is widely used in dermatology and specialized fields to measure erythemally effective irradiances (W m -2 eff.), or SEDs per hour. Still another, related quantity is the Global Solar UV Index used in public health to describe the risk of sunburn with weather and sun position. A UVI of 1.0 is slightly less [10% less] than one SED per hour. Both quantities are standardized by the International Commission on Illumination (CIE) and the International Standards Organization (ISO) as explained in the Appendix A (Joint ISO/CIE 1999/1998). 3.2.2.2 Tanning and adaptation of the skin The wide range of susceptibility to solar exposure among phototypes (Table 1) is due largely to the two types of melanin (eumelanin and phaeomelanin), (Young 2004, Césarini 1988), 20
Protecting Workers from Ultraviolet Radiation Eumelanin (black melanin) is produced by melanocytes upon alpha-MSH adsorption on MC1R gene product (receptor) at the surface of the melanocytes. Phaeomelanin (red melanin) is produced in melanocytes bearing MC1R variants. Phaeomelanin absorb UV photons and produce reactive oxygen species (ROS) which are phototoxic. Eumelanin (stable free radical) absorb UV photons and scavenge free radicals and are photoprotective. All individuals produce eumelanin and phaeomelanin in different ratios according to genetic makeup and as a consequence present large differences in solar sensitivity and skin cancer incidence. In addition, darker skin types have more efficient DNA repair than the skin phototypes I and II (Sheehan et al 2002). Skin adaptation from frequent UVR exposure is not only characterized by the obvious effect of skin darkening (“tanning” or “melanogenesis”), but also by skin thickening (Table 2). Thickening of the outermost layers of the skin (epidermis and stratum corneum) takes place as an adaptation to UVB-related damage. This can be a 3 to 5-fold thickening of the stratum corneum within one to seven weeks after several exposures to UVB, and returns to normal about one to two months after ceasing exposure. This thickening after sun exposure leads to a significant increase in UV protection by a factor of five or greater, and in lightly pigmented skin types, thickening is probably more important than tanning in providing protection. The thickening of the skin after prolonged tanning protects sensitive cells (basal keratinocytes, melanocytes) by absorbing UVB radiation before they reach the basal layer of the epidermis. After some shedding (peeling) of the stratum corneum, the basal layer can be directly stimulated by UVB and thus the thickening or protective processes recur and reach a steady state. However, in darkly pigmented individuals it is likely that skin pigmentation is the most important means of protection against UVR. Tanning becomes noticeable within a day or two after sun exposure, gradually increasing for several days and persisting for a week. Although a tanned skin does confer a degree of protection, this seems to be no more than a factor of two to three in the absence of skin thickening. The wavelengths of the radiation that induce tanning are very similar to those of radiation producing erythema. Table1 describes the range of skin types and sensitivity to UVR effects. Subjects with sun-reactive, melano-compromised (skin types I and II) are poor tanners compared to those with melano-competent (skin types III and IV) who tan well. Melanogenesis can be stimulated in individuals who tan well with solar UV doses that were considerably below the erythemal doses in the UVA region. Table 1. Classification of skin types based on their susceptibility to sunburn in sunlight and their ability to tan. Modified after Fitzpatrick and Bolognia, 1995 Skin phototype Sun sensitivity Sunburn susceptibility* Tanning achieved Classes of individuals I Very sensitive Always sunburn: < 2 SED No tan Melano-compromised II Moderately sensitive High: 2 – 3 SED Light tan Melano-compromised III Moderately insensitive Moderate: 3 - 5 SED Medium tan Melano-competent IV Insensitive Low: 5-7 SED Dark tan Melano-competent V Insensitive Very low: 7-10 SED Natural brown skin Melano-protected VI Insensitive Extremely low: > 10 SED Natural black skin Melano-protected *The ranges of SEDs are not prescriptive but only indicative 21
Page 1 and 2: Protecting Workers from Ultraviolet
Page 3 and 4: International Commission on Non-Ion
Page 5: PREFACE The objective of this book
Page 11 and 12: 1. Introduction Protecting Workers
Page 17 and 18: 3. Biological and Health Effects Pr
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Page 33 and 34: 4.5.5 Shading Protecting Workers fr
Page 35 and 36: 5.3.1 Welding Protecting Workers fr
Page 37 and 38: 5.3.6 Materials inspection Protecti
Page 41 and 42: where Protecting Workers from Ultra
Page 43 and 44: 7.4 CIE Risk Groups for Lamps Prote
Page 47 and 48: 8.3.4 Personal dosimeters Protectin
Page 49 and 50: 8.4.2 Orientation of the detector P
Page 67 and 68: 10.3 Administrative Control Measure
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APPENDIX A RADIOMETRIC TERMS AND UN
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Protecting Workers from Ultraviolet
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APPENDIX C Protecting Workers from
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APPENDIX E Protecting Workers from
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APPENDIX F Protecting Workers from
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REFERENCES Part II: Additional Refe
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ISBN 978-3-934994-07-2
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