Tuesday, 15 March 2011 15:01

Infrared Radiation

Written by
Rate this item
(10 votes)

Infrared radiation is that part of the non-ionizing radiation spectrum located between microwaves and visible light. It is a natural part of the human environment and thus people are exposed to it in small amounts in all areas of daily life—for example, at home or during recreational activities in the sun. Very intense exposure, however, may result from certain technical processes at the workplace.

Many industrial processes involve thermal curing of various kinds of materials. The heat sources used or the heated material itself will usually emit such high levels of infrared radiation that a large number of workers are potentially at risk of being exposed.

Concepts and Quantities

Infrared radiation (IR) has wavelengths ranging from 780 nm to 1 mm. Following the classification by the International Commission on Illumination (CIE), this band is subdivided into IRA (from 780 nm to 1.4 μm), IRB (from 1.4 μm to 3 μm) and IRC (from 3 μm to 1 mm). This subdivision approximately follows the wavelength-dependent absorption characteristics of IR in tissue and the resulting different biological effects.

The amount and the temporal and spatial distribution of infrared radiation are described by different radiometric quantities and units. Due to optical and physiological properties, especially of the eye, a distinction is usually made between small “point” sources and “extended” sources. The criterion for this distinction is the value in radians of the angle (α) measured at the eye that is subtended by the source. This angle can be calculated as a quotient, the light source dimension DL divided by the viewing distance r. Extended sources are those which subtend a viewing angle at the eye greater than αmin, which normally is 11 milliradians. For all extended sources there is a viewing distance where α equals αmin; at greater viewing distances, the source can be treated like a point source. In optical radiation protection the most important quantities concerning extended sources are the radiance (L, expressed in Wm–2sr–1) and the time-integrated radiance (Lp in Jm–2sr–1), which describe the “brightness” of the source. For health risk assessment, the most relevant quantities concerning point sources or exposures at such distances from the source where α< αmin, are the irradiance (E, expressed in Wm–2), which is equivalent to the concept of exposure dose rate, and the radiant exposure (H, in Jm–2), equivalent to the exposure dose concept.

In some bands of the spectrum, the biological effects due to exposure are strongly dependent on wavelength. Therefore, additional spectroradiometric quantities must be used (e.g., the spectral radiance, Ll, expressed in Wm–2 sr–1 nm–1) to weigh the physical emission values of the source against the applicable action spectrum related to the biological effect.

 

Sources and Occupational Exposure

Exposure to IR results from various natural and artificial sources. The spectral emission from these sources may be limited to a single wavelength (laser) or may be distributed over a broad wavelength band.

The different mechanisms for the generation of optical radiation in general are:

  • thermal excitation (black-body radiation)
  • gas discharge
  • light amplification by stimulated emission of radiation (laser), with the mechanism of gas discharge being of lesser importance in the IR band.

 

The emission from the most important sources used in many industrial processes results from thermal excitation, and can be approximated using the physical laws of black-body radiation if the absolute temperature of the source is known. The total emission (M, in Wm–2) of a black-body radiator (figure 1) is described by the Stefan-Boltzmann law:

M(T) = 5.67 x 10-8T4

and depends on the 4th power of the temperature (T, in K) of the radiating body. The spectral distribution of the radiance is described by Planck’s radiation law:

and the wavelength of maximum emission (λmax) is described according to Wien’s law by:

λmax = (2.898 x 10-8) / T

Figure 1. Spectral radiance λmaxof a black body radiator at the absolute temperature shown in degrees Kelvin on each curve

ELF040F1

Many lasers used in industrial and medical processes will emit very high levels of IR. In general, compared with other radiation sources, laser radiation has some unusual features that may influence the risk following an exposure, such as very short pulse duration or extremely high irradiance. Therefore, laser radiation is discussed in detail elsewhere in this chapter.

Many industrial processes require the use of sources emitting high levels of visible and infrared radiation, and thus a large number of workers like bakers, glass blowers, kiln workers, foundry workers, blacksmiths, smelters and fire-fighters are potentially at risk of exposure. In addition to lamps, such sources as flames, gas torches, acetylene torches, pools of molten metal and incandescent metal bars must be considered. These are encountered in foundries, steel mills and in many other heavy industrial plants. Table 1 summarizes some examples of IR sources and their applications.

Table 1. Different sources of IR, population exposed and approximate exposure levels

Source

Application or exposed population

Exposure

Sunlight

Outdoor workers, farmers, construction workers, seafarers, general public

500 Wm–2

Tungsten filament lamps

General population and workers
General lighting, ink and paint drying

105–106 Wm–2sr–1

Tungsten halogen filament lamps

(See tungsten filament lamps)
Copying systems (fixing), general processes (drying, baking, shrinking, softening)

50–200 Wm–2 (at 50 cm)

Light emitting diodes (e.g. GaAs diode)

Toys, consumer electronics, data transmission technology, etc.

105 Wm–2sr–1

Xenon arc lamps

Projectors, solar simulators, search lights
Printing plant camera operators, optical laboratory workers, entertainers

107 Wm–2sr–1

Iron melt

Steel furnace, steel mill workers

105 Wm–2sr–1

Infrared lamp arrays

Industrial heating and drying

103 to 8.103 Wm–2

Infrared lamps in hospitals

Incubators

100–300 Wm–2

 

Biological Effects

Optical radiation in general does not penetrate very deeply into biological tissue. Therefore, the primary targets of an IR exposure are the skin and the eye. Under most exposure conditions the main interaction mechanism of IR is thermal. Only the very short pulses that lasers may produce, but which are not considered here, can also lead to mechanothermal effects. Effects from ionization or from the breakage of chemical bonds are not expected to appear with IR radiation because the particle energy, being less than approximately 1.6 eV, is too low to cause such effects. For the same reason, photochemical reactions become significant only at shorter wavelengths in the visual and in the ultraviolet region. The different wavelength-dependent health effects of IR arise mainly from the wavelength-dependent optical properties of tissue—for example, the spectral absorption of the ocular media (figure 2).

Figure 2. Spectral absorption of the ocular media

ELF040F2

Effects on the eye

In general, the eye is well adapted to protect itself against optical radiation from the natural environment. In addition, the eye is physiologically protected against injury from bright light sources, such as the sun or high intensity lamps, by an aversion response that limits the duration of exposure to a fraction of a second (approximately 0.25 seconds).

IRA affects primarily the retina, because of the transparency of the ocular media. When directly viewing a point source or laser beam, the focusing properties in the IRA region additionally render the retina much more susceptible to damage than any other part of the body. For short exposure periods, heating of the iris from the absorption of visible or near IR is considered to play a role in the development of opacities in the lens.

With increasing wavelength, above approximately 1 μm, the absorption by ocular media increases. Therefore, absorption of IRA radiation by both the lens and the pigmented iris is considered to play a role in the formation of lenticular opacities. Damage to the lens is attributed to wavelengths below 3 μm (IRA and IRB). For infrared radiation of wavelengths longer than 1.4 μm, the aqueous humour and the lens are particularly strongly absorbent.

In the IRB and IRC region of the spectrum, the ocular media become opaque as a result of the strong absorption by their constituent water. Absorption in this region is primarily in the cornea and in the aqueous humour. Beyond 1.9 μm, the cornea is effectively the sole absorber. The absorption of long wavelength infrared radiation by the cornea may lead to increased temperatures in the eye due to thermal conduction. Because of a quick turnover rate of the surface corneal cells, any damage limited to the outer corneal layer can be expected to be temporary. In the IRC band the exposure can cause a burn on the cornea similar to that on the skin. Corneal burns are not very likely to occur, however, because of the aversion reaction triggered by the painful sensation caused by strong exposure.

Effects on the skin

Infrared radiation will not penetrate the skin very deeply. Therefore, exposure of the skin to very strong IR may lead to local thermal effects of different severity, and even serious burns. The effects on the skin depend on the optical properties of the skin, such as wavelength-dependent depth of penetration (figure 3 ). Especially at longer wavelengths, an extensive exposure may cause a high local temperature rise and burns. The threshold values for these effects are time dependent, because of the physical properties of the thermal transport processes in the skin. An irradiation of 10 kWm–2, for example, may cause a painful sensation within 5 seconds, whereas an exposure of 2 kWm–2 will not cause the same reaction within periods shorter than approximately 50 seconds.

Figure 3. Depth of penetration into the skin for different wavelengths

ELF040F3

If the exposure is extended over very long periods, even at values well below the pain threshold, the burden of heat to the human body may be great. Especially if the exposure covers the whole body as, for example, in front of a steel melt. The result may be an imbalance of the otherwise physiologically well balanced thermoregulation system. The threshold for tolerating such an exposure will depend on different individual and environmental conditions, such as the individual capacity of the thermoregulation system, the actual body metabolism during exposure or the environmental temperature, humidity and air movement (wind speed). Without any physical work, a maximum exposure of 300 Wm–2 may be tolerated over eight hours under certain environmental conditions, but this value decreases to approximately 140 Wm–2 during heavy physical work.

Exposure Standards

The biological effects of IR exposure which are dependent on wavelength and on the duration of exposure, are intolerable only if certain threshold intensity or dose values are exceeded. To protect against such intolerable exposure conditions, international organizations such as the World Health Organization (WHO), the International Labour Office (ILO), the International Committee for Non-Ionizing Radiation of the International Radiation Protection Association (INIRC/IRPA), and its successor, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the American Conference of Governmental Industrial Hygienists (ACGIH) have suggested exposure limits for infrared radiation from both coherent and incoherent optical sources. Most of the national and international suggestions on guidelines for limiting human exposure to infrared radiation are either based on or even identical with the suggested threshold limit values (TLVs) published by the ACGIH (1993/1994). These limits are widely recognized and are frequently used in occupational situations. They are based on current scientific knowledge and are intended to prevent thermal injury of the retina and cornea and to avoid possible delayed effects on the lens of the eye.

The 1994 revision of the ACGIH exposure limits is as follows:

1. For the protection of the retina from thermal injury in case of exposure to visible light, (for example, in the case of powerful light sources), the spectral radiance Lλ in W/(m² sr nm) weighted against the retinal thermal hazard function Rλ (see table 2) over the wavelength interval Δλ and summed over the range of wavelength 400 to 1400 nm, should not exceed:

where t is the viewing duration limited to intervals from 10-3 to 10 seconds (that is, for accidental viewing conditions, not fixated viewing), and α is the angular subtense of the source in radians calculated by α = maximum extension of the source/distance to the source Rλ  (table 2 ).

2. To protect the retina from the exposure hazards of infrared heat lamps or any near IR source where a strong visual stimulus is absent, the infrared radiance over the wavelength range 770 to 1400 nm as viewed by the eye (based on a 7 mm pupil diameter) for extended duration of viewing conditions should be limited to:

This limit is based on a pupil diameter of 7 mm since, in this case, the aversion response (closing the eye, for example) may not exist due to the absence of visible light.

3. To avoid possible delayed effects on the lens of the eye, such as delayed cataract, and to protect the cornea from overexposure, the infrared radiation at wavelengths greater than 770 nm should be limited to 100 W/m² for periods greater than 1,000 s and to:

or for shorter periods.

4. For aphakic patients, separate weighting functions and resulting TLVs are given for the wavelength range of ultraviolet and visible light (305–700 nm).

Table 2. Retinal thermal hazard function

Wavelength (nm)

Rλ

Wavelength (nm)

Rλ

400

1.0

460

8.0

405

2.0

465

7.0

410

4.0

470

6.2

415

8.0

475

5.5

420

9.0

480

4.5

425

9.5

485

4.0

430

9.8

490

2.2

435

10.0

495

1.6

440

10.0

500–700

1.0

445

9.7

700–1,050

10((700 - λ )/500)

450

9.4

1,050–1,400

0.2

455

9.0

   

Source: ACGIH 1996.

Measurement

Reliable radiometric techniques and instruments are available that make it possible to analyse the risk to the skin and the eye from exposure to sources of optical radiation. For characterizing a conventional light source, it is generally very useful to measure the radiance. For defining hazardous exposure conditions from optical sources, the irradiance and the radiant exposure are of greater importance. The evaluation of broad-band sources is more complex than the evaluation of sources that emit at single wavelengths or very narrow bands, since spectral characteristics and source size must be considered. The spectrum of certain lamps consists of both a continuum emission over a wide wavelength band and emission on certain single wavelengths (lines). Significant errors may be introduced into the representation of those spectra if the fraction of energy in each line is not properly added to the continuum.

For health-hazard assessment the exposure values must be measured over a limiting aperture for which the exposure standards are specified. Typically a 1 mm aperture has been considered to be the smallest practical aperture size. Wavelengths greater than 0.1 mm present difficulties because of significant diffraction effects created by a 1 mm aperture. For this wavelength band an aperture of 1 cm² (11 mm diameter) was accepted, because hot spots in this band are larger than at shorter wavelengths. For the evaluation of retinal hazards, the size of the aperture was determined by an average pupil size and therefore an aperture of 7 mm was chosen.

In general, measurements in the optical region are very complex. Measurements taken by untrained personnel may lead to invalid conclusions. A detailed summary of measurement procedures is to be found in Sliney and Wolbarsht (1980).

Protective Measures

The most effective standard protection from exposure to optical radiation is the total enclosure of the source and all of the radiation pathways that may exit from the source. By such measures, compliance with the exposure limits should be easy to achieve in the majority of cases. Where this is not the case, personal protection is applicable. For example, available eye protection in the form of suitable goggles or visors or protective clothing should be used. If the work conditions will not allow for such measures to be applied, administrative control and restricted access to very intense sources may be necessary. In some cases a reduction of either the power of the source or the working time (work pauses to recover from heat stress), or both, might be a possible measure to protect the worker.

Conclusion

In general, infrared radiation from the most common sources such as lamps, or from most industrial applications, will not cause any risk to workers. At some workplaces, however, IR can cause a health risk for the worker. In addition, there is a rapid increase in the application and use of special-purpose lamps and in high temperature processes in industry, science and medicine. If the exposure from those applications is sufficiently high, detrimental effects (mainly in the eye but also on the skin) cannot be excluded. The importance of internationally recognized optical radiation exposure standards is expected to increase. To protect the worker from excessive exposure, protective measures like shielding (eye shields) or protective clothing should be mandatory.

The principal adverse biological effects attributed to infrared radiation are cataracts, known as glass blower’s or furnaceman’s cataracts. Long-term exposure even at relatively low levels causes heat stress to the human body. At such exposure conditions additional factors such as body temperature and evaporative heat loss as well as environmental factors must be considered.

In order to inform and instruct workers some practical guides were developed in industrial countries. A comprehensive summary can be found in Sliney and Wolbarsht (1980).

 

Back

Read 17356 times Last modified on Thursday, 13 October 2011 21:31

" DISCLAIMER: The ILO does not take responsibility for content presented on this web portal that is presented in any language other than English, which is the language used for the initial production and peer-review of original content. Certain statistics have not been updated since the production of the 4th edition of the Encyclopaedia (1998)."

Contents

Preface
Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Barometric Pressure Increased
Barometric Pressure Reduced
Biological Hazards
Disasters, Natural and Technological
Electricity
Fire
Heat and Cold
Hours of Work
Indoor Air Quality
Indoor Environmental Control
Lighting
Noise
Radiation: Ionizing
Radiation: Non-Ionizing
Vibration
Violence
Visual Display Units
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides

Radiation: Non-Ionizng References

Allen, SG. 1991. Radiofrequency field measurements and hazard assessment. J Radiol Protect 11:49-62.

American Conference of Governmental Industrial Hygienists (ACGIH). 1992. Documentation for the Threshold Limit Values. Cincinnati, Ohio: ACGIH.

—. 1993. Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, Ohio: ACGIH.

—. 1994a. Annual Report of ACGIH Physical Agents Threshold Limit Values Committee. Cincinnati, Ohio: ACGIH.

—. 1994b. TLV’s, Threshold Limit Values and Biological Exposure Indices for 1994-1995. Cincinnati, Ohio: ACGIH.

—. 1995. 1995-1996 Threshhold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, Ohio: ACGIH.

—. 1996. TLVs© and BEIs©. Threshold Limit Values for Chemical Substances and Physical Agents; Biological Exposure Indices. Cincinnati, Ohio: ACGIH.

American National Standards Institute (ANSI). 1993. Safe Use of Lasers. Standard No. Z-136.1. New York: ANSI.

Aniolczyk, R. 1981. Measurements of hygienic evaluation of electromagnetic fields in the environment of diathermy, welders, and induction heaters. Medycina Pracy 32:119-128.

Bassett, CAL, SN Mitchell, and SR Gaston. 1982. Pulsing electromagnetic field treatment in ununited fractures and failed artrodeses. J Am Med Assoc 247:623-628.

Bassett, CAL, RJ Pawluk, and AA Pilla. 1974. Augmentation of bone repair by inductively coupled electromagnetic fields. Science 184:575-577.

Berger, D, F Urbach, and RE Davies. 1968. The action spectrum of erythema induced by ultraviolet radiation. In Preliminary Report XIII. Congressus Internationalis Dermatologiae, Munchen, edited by W Jadassohn and CG Schirren. New York: Springer-Verlag.

Bernhardt, JH. 1988a. The establishment of frequency dependent limits for electric and magnetic fields and evaluation of indirect effects. Rad Envir Biophys 27:1.

Bernhardt, JH and R Matthes. 1992. ELF and RF electromagnetic sources. In Non-Ionizing Radiation Protection, edited by MW Greene. Vancouver: UBC Press.

Bini, M, A Checcucci, A Ignesti, L Millanta, R Olmi, N Rubino, and R Vanni. 1986. Exposure of workers to intense RF electric fields that leak from plastic sealers. J Microwave Power 21:33-40.

Buhr, E, E Sutter, and Dutch Health Council. 1989. Dynamic filters for protective devices. In Dosimetry of Laser Radiation in Medicine and Biology, edited by GJ Mueller and DH Sliney. Bellingham, Wash: SPIE.

Bureau of Radiological Health. 1981. An Evaluation of Radiation Emission from Video Display Terminals. Rockville, MD: Bureau of Radiological Health.

Cleuet, A and A Mayer. 1980. Risques liés à l’utilisation industrielle des lasers. In Institut National de Recherche et de Sécurité, Cahiers de Notes Documentaires, No. 99 Paris: Institut National de Recherche et de Sécurité.

Coblentz, WR, R Stair, and JM Hogue. 1931. The spectral erythemic relation of the skin to ultraviolet radiation. In Proceedings of the National Academy of Sciences of the United States of America Washington, DC: National Academy of Sciences.

Cole, CA, DF Forbes, and PD Davies. 1986. An action spectrum for UV photocarcinogenesis. Photochem Photobiol 43(3):275-284.

Commission Internationale de L’Eclairage (CIE). 1987. International Lighting Vocabulary. Vienna: CIE.

Cullen, AP, BR Chou, MG Hall, and SE Jany. 1984. Ultraviolet-B damages corneal endothelium. Am J Optom Phys Opt 61(7):473-478.

Duchene, A, J Lakey, and M Repacholi. 1991. IRPA Guidelines On Protection Against Non-Ionizing Radiation. New York: Pergamon.

Elder, JA, PA Czerki, K Stuchly, K Hansson Mild, and AR Sheppard. 1989. Radiofrequency radiation. In Nonionizing Radiation Protection, edited by MJ Suess and DA Benwell-Morison. Geneva: WHO.

Eriksen, P. 1985. Time resolved optical spectra from MIG welding arc ignition. Am Ind Hyg Assoc J 46:101-104.

Everett, MA, RL Olsen, and RM Sayer. 1965. Ultraviolet erythema. Arch Dermatol 92:713-719.

Fitzpatrick, TB, MA Pathak, LC Harber, M Seiji, and A Kukita. 1974. Sunlight and Man, Normal and Abnormal Photobiologic Responses. Tokyo: Univ. of Tokyo Press.

Forbes, PD and PD Davies. 1982. Factors that influence photocarcinogenesis. Chap. 7 in Photoimmunology, edited by JAM Parrish, L Kripke, and WL Morison. New York: Plenum.

Freeman, RS, DW Owens, JM Knox, and HT Hudson. 1966. Relative energy requirements for an erythemal response of skin to monochromatic wavelengths of ultraviolet present in the solar spectrum. J Invest Dermatol 47:586-592.

Grandolfo, M and K Hansson Mild. 1989. Worldwide public and occupational radiofrequency and microwave protection. In Electromagnetic Biointeraction. Mechanisms, Safety Standards, Protection Guides, edited by G Franceschetti, OP Gandhi, and M Grandolfo. New York: Plenum.

Greene, MW. 1992. Non Ionizing Radiation. 2nd International Non Ionizing Radiation Workshop, 10-14 May, Vancouver.

Ham, WTJ. 1989. The photopathology and nature of the blue-light and near-UV retinal lesion produced by lasers and other optic sources. In Laser Applications in Medicine and Biology, edited by ML Wolbarsht. New York: Plenum.

Ham, WT, HA Mueller, JJ Ruffolo, D Guerry III, and RK Guerry. 1982. Action spectrum for retinal injury from near ultraviolet radiation in the aphakic monkey. Am J Ophthalmol 93(3):299-306.

Hansson Mild, K. 1980. Occupational exposure to radio-frequency electromagnetic fields. Proc IEEE 68:12-17.

Hausser, KW. 1928. Influence of wavelength in radiation biology. Strahlentherapie 28:25-44.

Institute of Electrical and Electronic Engineers (IEEE). 1990a. IEEE COMAR Position of RF and Microwaves. New York: IEEE.

—. 1990b. IEEE COMAR Position Statement On Health Aspects of Exposure to Electric and Magnetic Fields from RF Sealers and Dielectric Heaters. New York: IEEE.

—. 1991. IEEE Standard for Safety Levels With Respect to Human Exposure to Radiofrequency Electromagnetic Fields 3 KHz to 300 GHz. New York: IEEE.

International Commission on Non-Ionizing Radiation Protection (ICNIRP). 1994. Guidelines on Limits of Exposure to Static Magnetic Fields. Health Phys 66:100-106.

—. 1995. Guidelines for Human Exposure Limits for Laser Radiation.

ICNIRP statement. 1996. Health issues related to the use of hand-held radiotelephones and base transmitters. Health Physics, 70:587-593.

International Electrotechnical Commission (IEC). 1993. IEC Standard No. 825-1. Geneva: IEC.

International Labour Office (ILO). 1993a. Protection from Power Frequency Electric and Magnetic Fields. Occupational Safety and Health Series, No. 69. Geneva: ILO.

International Radiation Protection Association (IRPA). 1985. Guidelines for limits of human exposure to laser radiation. Health Phys 48(2):341-359.

—. 1988a. Change: Recommendations for minor updates to the IRPA 1985 guidelines on limits of exposure to laser radiation. Health Phys 54(5):573-573.

—. 1988b. Guidelines on limits of exposure to radiofrequency electromagnetic fields in the frequency range from 100 kHz to 300 GHz. Health Phys 54:115-123.

—. 1989. Proposed change to the IRPA 1985 guidelines limits of exposure to ultraviolet radiation. Health Phys 56(6):971-972.

International Radiation Protection Association (IRPA) and International Non-Ionizing Radiation Committee. 1990. Interim guidelines on limits of exposure to 50/60 Hz electric and magnetic fields. Health Phys 58(1):113-122.

Kolmodin-Hedman, B, K Hansson Mild, E Jönsson, MC Anderson, and A Eriksson. 1988. Health problems among operations of plastic welding machines and exposure to radiofrequency electromagnetic fields. Int Arch Occup Environ Health 60:243-247.

Krause, N. 1986. Exposure of people to static and time variable magnetic fields in technology, medicine, research and public life: Dosimetric aspects. In Biological Effects of Static and ELF-Magnetic Fields, edited by JH Bernhardt. Munchen: MMV Medizin Verlag.

Lövsund, P and KH Mild. 1978. Low Frequency Electromagnetic Field Near Some Induction Heaters. Stockholm: Stockholm Board of Occupational Health and Safety.

Lövsund, P, PA Oberg, and SEG Nilsson. 1982. ELF magnetic fields in electrosteel and welding industries. Radio Sci 17(5S):355-385.

Luckiesh, ML, L Holladay, and AH Taylor. 1930. Reaction of untanned human skin to ultraviolet radiation. J Optic Soc Am 20:423-432.

McKinlay, AF and B Diffey. 1987. A reference action spectrum for ultraviolet induced erythema in human skin. In Human Exposure to Ultraviolet Radiation: Risks and Regulations, edited by WF Passchier and BFM Bosnjakovic. New York: Excerpta medica Division, Elsevier Science Publishers.

McKinlay, A, JB Andersen, JH Bernhardt, M Grandolfo, K-A Hossmann, FE van Leeuwen, K Hansson Mild, AJ Swerdlow, L Verschaeve and B Veyret. Proposal for a research programme by a European Commission Expert Group. Possible health effects related to the use of radiotelephones. Unpublished report.

Mitbriet, IM and VD Manyachin. 1984. Influence of magnetic fields on the repair of bone. Moscow, Nauka, 292-296.

National Council on Radiation Protection and Measurements (NCRP). 1981. Radiofrequency Electromagnetic Fields. Properties, Quantities and Units, Biophysical Interaction, and Measurements. Bethesda, MD: NCRP.

—. 1986. Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields. Report No. 86. Bethesda, MD: NCRP.

National Radiological Protection Board (NRPB). 1992. Electromagnetic Fields and the Risk of Cancer. Vol. 3(1). Chilton, UK: NRPB.

—. 1993. Restrictions On Human Exposure to Static and Time-Varying Electromagnetic Fields and Radiations. Didcot, UK: NRPB.

National Research Council (NRC). 1996. Possible health effects of exposure to residential electric and magnetic fields. Washington: NAS Press. 314.

Olsen, EG and A Ringvold. 1982. Human corneal endothelium and ultraviolet radiation. Acta Ophthalmol 60:54-56.

Parrish, JA, KF Jaenicke, and RR Anderson. 1982. Erythema and melanogenesis: Action spectra of normal human skin. Photochem Photobiol 36(2):187-191.

Passchier, WF and BFM Bosnjakovic. 1987. Human Exposure to Ultraviolet Radiation: Risks and Regulations. New York: Excerpta Medica Division, Elsevier Science Publishers.

Pitts, DG. 1974. The human ultraviolet action spectrum. Am J Optom Phys Opt 51(12):946-960.

Pitts, DG and TJ Tredici. 1971. The effects of ultraviolet on the eye. Am Ind Hyg Assoc J 32(4):235-246.

Pitts, DG, AP Cullen, and PD Hacker. 1977a. Ocular effects of ultraviolet radiation from 295 to 365nm. Invest Ophthalmol Vis Sci 16(10):932-939.

—. 1977b. Ultraviolet Effects from 295 to 400nm in the Rabbit Eye. Cincinnati, Ohio: National Institute for Occupational Safety and Health (NIOSH).

Polk, C and E Postow. 1986. CRC Handbook of Biological Effects of Electromagnetic Fields. Boca Raton: CRC Press.

Repacholi, MH. 1985. Video display terminals -should operators be concerned? Austalas Phys Eng Sci Med 8(2):51-61.

—. 1990. Cancer from exposure to 50760 Hz electric and magnetic fields: A major scientific debate. Austalas Phys Eng Sci Med 13(1):4-17.

Repacholi, M, A Basten, V Gebski, D Noonan, J Finnic and AW Harris. 1997. Lymphomas in E-Pim1 transgenic mice exposed to pulsed 900 MHz electromagnetic fields. Radiation research, 147:631-640.

Riley, MV, S Susan, MI Peters, and CA Schwartz. 1987. The effects of UVB irradiation on the corneal endothelium. Curr Eye Res 6(8):1021-1033.

Ringvold, A. 1980a. Cornea and ultraviolet radiation. Acta Ophthalmol 58:63-68.

—. 1980b. Aqueous humour and ultraviolet radiation. Acta Ophthalmol 58:69-82.

—. 1983. Damage of the corneal epithelium caused by ultraviolet radiation. Acta Ophthalmol 61:898-907.

Ringvold, A and M Davanger. 1985. Changes in the rabbit corneal stroma caused by UV radiation. Acta Ophthalmol 63:601-606.

Ringvold, A, M Davanger, and EG Olsen. 1982. Changes of the corneal endothelium after ultraviolet radiation. Acta Ophthalmol 60:41-53.

Roberts, NJ and SM Michaelson. 1985. Epidemiological studies of human exposure to radiofrequency radiation: A critical review. Int Arch Occup Environ Health 56:169-178.

Roy, CR, KH Joyner, HP Gies, and MJ Bangay. 1984. Measurement of electromagnetic radiation emitted from visual display terminals (VDTs). Rad Prot Austral 2(1):26-30.

Scotto, J, TR Fears, and GB Gori. 1980. Measurements of Ultraviolet Radiations in the United States and Comparisons With Skin Cancer Data. Washington, DC: US Government Printing Office.

Sienkiewicz, ZJ, RD Saunder, and CI Kowalczuk. 1991. Biological Effects of Exposure to Non-Ionizing Electromagnetic Fields and Radiation. 11 Extremely Low Frequency Electric and Magnetic Fields. Didcot, UK: National Radiation Protection Board.

Silverman, C. 1990. Epidemiological studies of cancer and electromagnetic fields. In Chap. 17 in Biological Effects and Medical Applications of Electromagnetic Energy, edited by OP Gandhi. Engelwood Cliffs, NJ: Prentice Hall.

Sliney, DH. 1972. The merits of an envelope action spectrum for ultraviolet radiation exposure criteria. Am Ind Hyg Assoc J 33:644-653.

—. 1986. Physical factors in cataractogenesis: Ambient ultraviolet radiation and temperature. Invest Ophthalmol Vis Sci 27(5):781-790.

—. 1987. Estimating the solar ultraviolet radiation exposure to an intraocular lens implant. J Cataract Refract Surg 13(5):296-301.

—. 1992. A safety manager’s guide to the new welding filters. Welding J 71(9):45-47.
Sliney, DH and ML Wolbarsht. 1980. Safety With Lasers and Other Optical Sources. New York: Plenum.

Stenson, S. 1982. Ocular findings in xeroderma pigmentosum: Report of two cases. Ann Ophthalmol 14(6):580-585.

Sterenborg, HJCM and JC van der Leun. 1987. Action spectra for tumourigenesis by ultraviolet radiation. In Human Exposure to Ultraviolet Radiation: Risks and Regulations, edited by WF Passchier and BFM Bosnjakovic. New York: Excerpta Medica Division, Elsevier Science Publishers.

Stuchly, MA. 1986. Human exposure to static and time-varying magnetic fields. Health Phys 51(2):215-225.

Stuchly, MA and DW Lecuyer. 1985. Induction heating and operator exposure to electromagnetic fields. Health Phys 49:693-700.

—. 1989. Exposure to electromagnetic fields in arc welding. Health Phys 56:297-302.

Szmigielski, S, M Bielec, S Lipski, and G Sokolska. 1988. Immunologic and cancer related aspects of exposure to low-level microwave and radiofrequency fields. In Modern Bioelectricity, edited by AA Mario. New York: Marcel Dekker.

Taylor, HR, SK West, FS Rosenthal, B Munoz, HS Newland, H Abbey, and EA Emmett. 1988. Effect of ultraviolet radiation on cataract formation. New Engl J Med 319:1429-1433.

Tell, RA. 1983. Instrumentation for measurement of electromagnetic fields: Equipment, calibrations, and selected applications. In Biological Effects and Dosimetry of Nonionizing Radiation, Radiofrequency and Microwave Energies, edited by M Grandolfo, SM Michaelson, and A Rindi. New York: Plenum.

Urbach, F. 1969. The Biologic Effects of Ultraviolet Radiation. New York: Pergamon.

World Health Organization (WHO). 1981. Radiofrequency and microwaves. Environmental Health Criteria, No.16. Geneva: WHO.

—. 1982. Lasers and Optical Radiation. Environmental Health Criteria, No. 23. Geneva: WHO.

—. 1987. Magnetic Fields. Environmental Health Criteria, No.69. Geneva: WHO.

—. 1989. Non-Ionization Radiation Protection. Copenhagen: WHO Regional Office for Europe.

—. 1993. Electromagnetic Fields 300 Hz to 300 GHz. Environmental Health Criteria, No. 137. Geneva: WHO.

—. 1994. Ultraviolet Radiation. Environmental Health Criteria, No. 160. Geneva: WHO.

World Health Organization (WHO), United Nations Environmental Programme (UNEP), and International Radiation Protection Association (IRPA). 1984. Extremely Low Frequency (ELF). Environmental Health Criteria, No. 35. Geneva: WHO.

Zaffanella, LE and DW DeNo. 1978. Electrostatic and Electromagnetic Effects of Ultra-High-Voltage Transmission Lines. Palo Alto, Calif: Electric Power Research Institute.

Zuclich, JA and JS Connolly. 1976. Ocular damage induced by near-ultraviolet laser radiation. Invest Ophthalmol Vis Sci 15(9):760-764.