EHC 23 on Lasers - 1982

ISBN: 92-4-154083-4

Environmental Health Criteria 23: Lasers and Optical Radiation. Geneva: World Health Organization; 1982.

Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, the International Radiation Protection Association (IRPA-INIRC), and the World Health Organization - © WHO, Geneva, 1982.

Excerpt of the preface: "Modern advances in science and technology have changed man's environment, introducing new factors which, besides their intended beneficial uses, may also have untoward side effects. Both the general public and health authorities are aware of the dangers ofpollution by chemicals, ionizing radiation, and noise, and of the need to take appropriate steps for effective control. The rapid growth of electro-optics and laser technology and the increasing use of electro-optical devices and lasers, including optical scanning equipment, high-intensity lamps, welding arcs, and UV photo-curing equipment, alignment lasers, and medical lasers have increased the possibility of human exposure to optical radiation and, at the same time, concern about health effects.

This document provides information on the physical aspects of electromagnetic radiation in the optical spectrum, within the wavelength range of 100 nm - 1 mm. Optical radiation includes ultraviolet radiation (UVR) from approximately 100 nm to 400 nm, light (visible radiation) from approximately 400 nm to 760 nm, and infrared radiation from approximately 760 nm to 1 mm. Each of these spectral regions can be arbitrarily divided into subregions. Lasers are capable of producing optical radiation in all three major divisions of the optical spectrum. A brief survey of lasers and other man-made sources of optical radiation is presented. It is known that optical radiation interacts with biological systems and a summary of knowledge on biological effects and health aspects has been included in this document. In a few countries, concern about occupational and public health aspects has led to the development of radiation protection guides and the establishment of exposure limits for laser radiation and UVR. Several countries are considering the introduction of recommendations or legislation concerned with protection against untoward effects from non-ionizing radiation in the optical spectrum. In others, efforts are being made to revise and update existing standards. It is hoped that this criteria document may provide useful information for the development, at a national level, of protection measures against non-ionizing radiation."

CONTENTS

ENVIRONMENTAL HEALTH CRITERIA FOR LASERS AND OPTICAL RADIATION

1. SUMMARY AND RECOMMENDATIONS FOR FURTHER STUDIES
     1.1. Summary
           1.1.1. Scope
           1.1.2. Optical radiation exposure
           1.1.3. Present health and safety standards
     1.2. Recommendations for further studies

2. DEFINITIONS OF OPTICAL RADIATION
     2.1. The electromagnetic spectrum
     2.2. Interaction of electromagnetic radiation with matter
           2.2.1. Interaction at an interface
                   2.2.1.1   Reflection
                   2.2.1.2   Refraction
           2.2.2. Interaction with a medium
                   2.2.2.1   Transmission
                   2.2.2.2   Attenuation
           2.2.3. Interference, diffraction and scattering effects
                   2.2.3.1   Interference and diffraction
                   2.2.3.2   Scattering

3. SOURCES OF RADIATION
     3.1. Molecular and atomic transitions

4. LASERS
     4.1. The laser medium
     4.2. The pumping system
     4.3. The resonant optical cavity
     4.4. Types of lasers
           4.4.1. Active media
           4.4.2. Temporal modes of operation
     4.5. Spatial (TEM) modes
     4.6. Beam characteristics
           4.6.1. Beam diameter
           4.6.2. Beam divergence
           4.6.3. Beam irradiance versus range for a circular beam
           4.6.4. Hot spots
           4.6.5. Coherence

5. RADIOMETRIC CONCEPTS
     5.1. Radiometric and photometric terminology
     5.2. Extended sources versus point sources
     5.3. Inverse square law

6. RADIOMETRIC AND PHOTOMETRIC MEASUREMENT
     6.1. Introduction
     6.2. Measurement instrumentation
           6.2.1. Thermal detectors
           6.2.2. Quantum detectors
           6.2.3. Detectors to resolve short pulses
           6.2.4. Safety meters
           6.2.5. Spectroradiometers
     6.3. Biological weighting of spectroradiometric data

7. BIOLOGICAL EFFECTS
     7.1. Thermal injury
     7.2. Photochemical injury
     7.3. Threshold of injury
           7.3.1. Means of determining thresholds of injury

8. EFFECTS OF OPTICAL RADIATION ON THE EYE
     8.1. Anatomy and physiology of the human eye
           8.1.1. The cornea
           8.1.2. The lens
           8.1.3. The retina and choroid
     8.2. Spectral properties of the eye
     8.3. Injury to the anterior portion of the eye
           8.3.1. Effects on the cornea
           8.3.2. UVR lenticular effects
           8.3.3. Infrared cataract
     8.4. Retinal injury
           8.4.1. Determining the retinal exposure
                   8.4.1.1   Pupil size
                   8.4.1.2   Spectral transmission of the ocular
                             media and spectral absorption by the
                             retina and choroid
                   8.4.1.3   Optical image quality
                   8.4.1.4   Small images
                   8.4.1.5   Retinal pigment epithelium (RPE)
                             absorption
           8.4.2. Chorioretinal thermal injury
           8.4.3. Location of retinal burns
     8.5. Photochemical retinal injury
           8.5.1. Very long-term exposure
     8.6. Flash blindness
     8.7. Discomfort glare
     8.8. Flashing lights

9. THE SKIN
     9.1. Anatomy
     9.2. Body heat regulation
     9.3. Optical properties
     9.4. Penetration depth and reflection
           9.4.1. Injury to the skin
           9.4.2. The sensation of warmth and heat flow
           9.4.3. Thermal injury threshold for the skin
           9.4.4. Delayed effects
           9.4.5. Ambient environment and heat stress
           9.4.6. UVR effects on the skin
           9.4.7. Photosensitization
           9.4.8. Photoallergy

10. LASER SAFETY STANDARDS: RATIONALE AND CURRENT STANDARDS
     10.1. Introduction
     10.2. Laser hazard classification

11. EXPOSURE LIMITS
     11.1. Rationale
     11.2. Assessment of the "safety factor"
     11.3. Environmental considerations
     11.4. Limiting apertures
           11.4.1. The 1-mm aperture
           11.4.2. The 11-mm aperture
           11.4.3. The 7-mm aperture
           11.4.4. The 80-mm aperture
     11.5. Spectral dependence of exposure limits
     11.6. Repetitively pulsed laser exposure
     11.7. Restriction for special applications (Class 3a)
     11.8. Present standards of exposure
           11.8.1. Laser standards
                   11.8.1.1 Exposure limits
                   11.8.1.2 Repetitively pulsed lasers
                   11.8.1.3 Extended source laser exposure
                   11.8.1.4 Restrictions on ELs
           11.8.2. Standards for non-laser sources
                   11.8.2.1 Introduction
                   11.8.2.2 UVR criteria
                   11.8.2.3 Retinal health criteria
                   11.8.2.4 Retinal thermal risk evaluation
                   11.8.2.5 Retinal blue-light risk evaluation
                   11.8.2.6 IR-A risk analysis
           11.8.3. Infrared standards

12. RISK EVALUATION
     12.1. Laser hazard classification
     12.2. Environmental considerations including
           reflection and the probability of exposure
           12.2.1. Reflections
           12.2.2. Retroreflection
           12.2.3. Optically aided viewing

13. ACCIDENTAL INJURIES

14. CONTROL MEASURES

15. HAZARDS OF LAMP SOURCES AND PROJECTION SYSTEMS

16. PROJECTION OPTICS

17. SAFETY GUIDELINES FOR HIGH-INTENSITY SOURCES

18. WELDING ARCS

19. EYE AND SKIN PROTECTION
     19.1. Laser safety eyewear
     19.2. Welders' filters
     19.3. Eye protection for furnace radiation
     19.4. Eye protection filters for solar radiation
     19.5. Skin-protecting agents for UVR (Sunscreens)
     19.6. Protective garments

20. MEDICAL SURVEILLANCE (RATIONALE)

21. FORMAL TEACHING FOR LASER WORKERS

REFERENCES

GLOSSARY

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