2 2. American Conference of Governmental Industrial Hygienists (ACGIH) (2019). TLVs and BEIs Based on the Documentation of the Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices. Cincinnati, OH: ACGIH.
3 3. International Commission on Non‐Ionizing Radiation Protection (ICNIRP) (2013). ICNIRP guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1000 μm. Health Phys 105 (3): 271–295.
4 4. Sliney, D.H. (2003). Ophthalmic laser safety. In: Lasers in Ophthalmology (ed. F. Fankhauser and S. Kwansniewska), 1–10. The Hague: Kugler Publications.
5 5. American National Standards Institute (ANSI) (2014). American National Standard Z136.1 for Safe Use of Lasers. Orlando, FL: Laser Institute of America.
6 6. International Electrotechnical Commission (IEC) (2014). Safety of Laser Products. Part 1: Equipment Classification and Requirements. IEC 60825‐1:2014, 3e. Geneva/Switzerland: IEC.
7 7. Barat, K. (2017). Laser Safety: Tools and Training, 2e. Boca Raton, FL: CRC Press.
8 8. Henderson, R. and Schulmeister, K. (2003). Laser Safety. Bristol: Institute of Physics Publishing.
9 9. Sliney, D.H. and Wolbarsht, M.L. (1980). Safety with Lasers and Other Optical Sources. New York, NY: Plenum Publishing.
10 10. Sliney, D.H. and Trokel, S.L. (1993). Medical Lasers and Their Safe Use. New York, NY: Springer‐Verlag.
11 11. Hadler, J. and Dowell, M. (2013). Accurate, inexpensive testing of laser pointer power for safe operation. Meas Sci Technol 24 (045202): 7.
12 12. Renk, K.F. (2017). Basics of Laser Physics. New York, NY: Springer.
13 13. Steen, W. and Mazumder, J. (2010). Laser Material Processing. New York, NY: Springer.
14 14. Svelto, O. (2010). Principles of Lasers, 5e. New York, NY: Plenum Publishing.
15 15. Young, M. (2000). Optics and Lasers, Including Fibers and Optical Waveguides. New York, NY: Springer‐Verlag.
16 16. Sliney, D.H., Mellerio, J., Gabel, V.P., and Schulmeister, K. (2002). What is the meaning of threshold in laser injury experiments? Implications for human exposure limits. Health Phys 82 (3): 335–347.
17 17. Laser Institute of America (LIA) (2019). LIA Laser Safety Guide. Orlando, FL: LIA.
18 18. Lund, D.J. and Sliney D.H. (2014). A new understanding of multiple‐pulsed laser‐induced retinal injury thresholds. Health Phys 106 (4): 505–515.
19 19. Mainster, M.A., Sliney, D.H., Marshall, J. et al. (1997). But is it really light damage? Ophthalmology 104 (2): 179–180.
20 20. Lyon, T.L. (1993). Laser measurement techniques guide for hazard evaluation. J Laser Appl 5 (1): 53–58. and 5(2): 37–42.
21 21. American National Standards Institute (ANSI) (2019). American National Standard Z136.7 for Testing and Labeling of Laser Protective Equipment. Orlando: Laser Institute of America.
22 22. European Committee for Standardization (CEN) (2017). Personal eye‐protection – filters and eye‐protectors against laser radiation (laser eye‐protectors). EN 207.
23 23. European Committee for Standardization (CEN) (2009). Personal eye protection – eye‐protectors for adjustment work on lasers and laser systems (laser adjustment eye‐protectors). EN 208.
24 24. Goldberg, D.J. (ed.) (2013). Laser Dermatology. New York, NY: Springer.
25 25. Sliney, D.H. and LeBodo, H. (1990). Laser eye protection. J Las Appl 2: 9.
NONIONIZING RADIATION: BROADBAND OPTICAL*
Margaret L. Phillips Ph.D. CIHand Allene H. Butler MA CIH CSP CHMM
1 INTRODUCTION
Optical radiation is the term applied collectively to ultraviolet (UV), visible, and infrared (IR) radiation, encompassing the portion of the electromagnetic spectrum between X‐rays and radiowaves. The common term “light” may be considered synonymous with visible radiation, that is, with the portion of the optical radiation spectrum that can be visually perceived by humans. However, “light” and related terms are sometimes used colloquially to include UV radiation and IR radiation as well as visible radiation.
Common sources of potentially harmful levels of optical radiation include the sun, welding and plasma arcs, xenon lamps, mercury lamps, “black lights”, sunlamps, germicidal lamps, excimer lamps, light‐emitting diodes (LEDs), incandescent lamps, heat lamps, industrial ovens and furnaces, and very hot or molten glass and metal. All of these sources may be considered broadband optical radiation sources because they produce radiation of multiple wavelengths, in most cases over a continuum. In contrast to broadband sources, lasers produce optical radiation that is monochromatic and coherent. Laser hazards are addressed in Nonionizing Radiation: Lasers of this volume.
The main target organs for optical radiation are the eye and skin. The potential short‐term adverse effects of overexposure to UV radiation are burning of the skin (erythema) and painful inflammation of the cornea of the eye (photokeratitis). UV radiation is the only type of nonionizing electromagnetic radiation that is a known human carcinogen, causing several types of skin cancer (1). Chronic overexposure to UV radiation may also result in cataract (clouding of the lens of the eye), premature aging of the skin, and immunosuppression. Acute overexposure of the eye to visible and near‐IR radiation may cause temporary or permanent retinal injury resulting in loss of visual acuity. The retina may be somewhat protected from acute overexposure to visible radiation by constriction of the pupil and by the aversion response, which causes the viewer to blink and look away within about 0.25 seconds of seeing an intense light. However, not all people exhibit an aversion response (2); moreover, the aversion response may be voluntarily overridden during viewing tasks. Chronic overexposure to blue light is associated with age‐related macular degeneration, a condition that can cause loss of central vision. Absorption of IR radiation causes heating of tissue. If the rate of radiant heat absorption by the tissue exceeds the rate that heat is dissipated from the tissue through blood circulation and other means, overheating or burning of the irradiated area of the skin or eyes can result. Radiant heat absorption from IR sources may also contribute to whole‐body heat stress. Chronic exposure to IR radiation may contribute to lens opacities, the so‐called “glassblowers' cataract.” A thorough review of the biological effects of optical radiation can be found in Infrared, Visible, and Ultraviolet Radiation (3).
Optical radiation exposure is as old as life under the sun, but new sources of exposure arise from new technologies. Recognition, evaluation, and control of any optical radiation exposure in the workplace begin with the characterization of the broadband radiation sources. Section 2 reviews the basic science of optical radiation and introduces the specialized terms and units used to characterize radiation sources and radiation exposures; this is the necessary background for applying exposure standards and interpreting measurements. Section 3 discusses the characteristics of common optical radiation sources. Section 4 addresses the quantitative assessment of optical radiation hazards and Section 5 describes the basic principles for control of these hazards. Section 6 provides some practical discussion of hazard recognition and control for specific processes or sources.
2 BASIC PHYSICS OF OPTICAL RADIATION
2.1 Nature of Optical Radiation
All electromagnetic radiation, including optical radiation, has the same essential physical nature. Electromagnetic radiation is a form of energy that propagates through space as mutually perpendicular oscillating electric and magnetic fields. (See Figure 4 from Ionizing Radiation.) The wave‐like nature of electromagnetic