Human exposure to nonionizing radiant energy—Potential hazards and safety standards

During the last quarter century there has been a marked development and increased utilization of equipment and devices for military, industrial, consumer-use, entertainment, and medical applications that emit a large variety of nonionizing radiant energies. These include ultraviolet, infrared, visible light, microwaves, and radio-frequency waves, which are all classified as electromagnetic waves. Many of the electro-magnetic waves at certain frequencies, power levels, and exposure durations can produce biological effects or injury depending on multiple physical and biological variables. Although equipment which utilizes or emits electromagnetic waves provides immeasurable benefits to mankind, it may also create potential hazards to the individual through uncontrolled and excessive radiation emissions. Consequently, questions are being raised such as: 1) How serious are these problems, what are their dimensions, and what acute and/or chronic effects on the human body may be involved? 2) How adequate is our present knowledge about personnel hazards of these radiation types? 3) How can exposure be reduced? 4) How can better regulation be obtained to reduce exposure? This paper reviews the pathophysiology of exposure to ultraviolet, infrared, coherent electromagnetic radiation (laser), microwaves, and radio-frequency radiation, and the protection guides which have been established for these energies. It is also pointed out that there is a need to set limits on the amount of exposure individuals can accept with safety; setting standards, however, is a very complicated process. The objectives of protection are to prevent acute effects and to limit the risks of late effects. The second objective, namely, to limit the risk of possible late effects, becomes difficult. Protection standards are the results of empirical approaches to various problems reflecting current qualitative and quantitative knowledge. A numerical value for a standard of effect implies a knowledge of the effect produced at a given level of stress, and that both effect and stress are measurable. One problem is the definition of what an "effect" is and whether it can ultimately be shown to modify man's "way of life" or that of his offspring. If there were a clear-cut relationship between exposure level and pathophysiologic effect, the problem of setting standards would be greatly simplified. Not only are there numerous variables to be considered, but it is often difficult or impossible to obtain the necessary data to draw valid conclusions concerning effects of exposure to various radiant energies. It is important to maintain a proper perspective, and assess realistically the biomedical effects of these radiant energies so that the worker or general public will not be unduly exposed nor will research, development, and beneficial utilization of these energies be hampered or restricted by an undue concern for effects which may be nonexistent or minimal in comparison to other environmental hazards. There is a need for scientific competence--research aimed at creating credible knowledge and data which can stand against the pressure of legal challenge as well as the understandable bias of special interest groups.