Radiant Energy

RADIANT ENERGY, electromagnetic oscillations of various frequencies and, correspondingly, of various wavelengths. This group, diverse in its properties and united under the term "radiant energy," includes infrared rays with a wavelength of 0.3 mm - 0.75 μ, visible light rays from red (750 mμ) to violet (400 mμ), ultraviolet rays (400 mμ - 10 mμ), X-rays (10 mμ - 0.1 Å), and radium rays (1Å = 0.01 Å). Their biological and therapeutic action is extremely diverse and is determined primarily by the wavelength of the respective rays and the degree of penetrability of the organism's tissues for them. Biological action of radiant energy. At the base of the diverse influence of radiant energy on biological objects lies the effect of rays on the course of physical, physicochemical, and chemical processes. As an example, one can cite ionization and charge exchange under the influence of ultraviolet rays, changes in the magnitude of surface tension, viscosity, and permeability; and among influences on chemical processes, the polymerization of oxygen molecules into ozone molecules, and processes of splitting, oxidation, and reduction. For details on the biological action of individual types of radiant energy, see Light, Heat, X-rays, Infrared rays, Ultraviolet rays. Action of radiant energy on humans in the work environment. In industry, we encounter the thermal effect of radiant energy on workers wherever there are heating installations (furnaces, hearths, etc.) or heated objects. The intensity of radiation and its spectral composition depend mainly on the temperature of heating of these sources. Other things being equal, the total radiation energy according to the Stefan-Boltzmann law is fourth-power proportional to the absolute temperature of the radiating body. In industry, we encounter radiations with various spectra: either continuous, solid, emanating from heated solid and liquid bodies, or discontinuous, banded, the source of which is heated gases. The energy of individual sections of the spectrum in the former is located in such a way that in a certain section, entirely characteristic of each heating temperature, the amount of radiation energy is maximal, dropping steeply towards short rays and more gently towards long rays. This dependence is expressed by Wien's formula: 3_max • T = K, where 3_max is the wavelength (in microns) of that spectral region ENERGY

in which the maximum radiation energy is located, T is the absolute heating temperature, and K is a constant equal to 2,960. This formula makes it possible to conclude that for the vast majority of industrial radiation sources, the maximum of their energy falls on the infrared part of the spectrum, and almost all the energy of their total flux falls on infrared radiation; in contrast to this, the maximum energy of the solar spectrum is located at 3_max = 0.5 μ, which corresponds to a temperature of 6,000°. The next feature of radiation encountered in industry is the nature of its propagation in the form of diverging, rather than parallel, rays (as in solar radiation). This circumstance makes a number of measuring instruments designed for the parallel course of solar radiation unsuitable for use in industry. Only the actinometer model specially designed by Professor Kalitin proved suitable for use in industrial conditions, making it possible to determine radiation with an intensity of 20-30 calories and, thanks to the simplicity of working with it, having already found widespread use in sanitary and hygienic practice (see Actinometry). In industrial conditions, one encounters stationary sources of radiant energy (hearths, furnaces, etc.) and mobile ones (workpieces, ingots, etc.). Among the former, we distinguish sources with an open flame (for example, hearths), as well as heated objects radiating energy into space, and sources surrounded by some kind of shell that delays the flow of radiant energy (e.g., furnaces). In the latter, the intensity of radiation can fluctuate greatly depending on the state of the shell, the presence of openings, the opening or closing of lids and dampers, etc. Maximum radiation intensities are observed precisely at these sources; thus, for example, in open-hearth furnaces with closed dampers, with significant wear and the presence of gaps around them, a radiation intensity of up to 10 calories was established at a distance of 1.5 m. When loading windows are opened, the radiation intensity at a distance of 1 m can reach 30-40 calories or more. (For comparison, let us note that the thermal effect of solar radiation at the Earth's surface boundary, according to Abbot, does not exceed 1.937 calories.) From other observations in industry, the following data can be cited: at Girders heating pits in rolling shops at a distance of 1 m, 0.51-3.5 calories were found; at sheet-rolling mills at the moment of rolling at a distance of 1 m, 13.8 calories; in steelmaking at Siemens furnaces during their heating from 1,600-2,100°, 10.5-16.5 calories, at a distance of 3 m, 1.2-2.0 calories; radiation from pouring steel when measured directly near the molds, 17.85-20.34 calories, at a distance of 1 m, 4.0-4.8 calories. In smithies, the sources of radiation are either hearths, where an intensity of 1.0 to 13.0 calories was observed, or processed objects, 487

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the intensity of which depends on the area of the radiating surface. In glass-melting furnaces, the intensity of radiation at the workplace was 0.2-10 calories. All authors note the extreme unevenness in the distribution of radiant energy in space. The main factor determining the degree of thermal effect of radiant energy on the worker, besides intensity, is the duration of continuous exposure, which varies greatly depending on the nature of the production processes. The duration and frequency of breaks in exposure, the state of the surrounding air (its temperature, humidity, mobility, and transparency), and finally the severity of the labor itself are also of serious importance. The area of the irradiated body surface is also of great importance; in this regard, sharp differences are observed in production. Exposure from all sides is particularly distressing, which for example occurs when unloading fired products from porcelain and faience kilns. For each production, there exist quite characteristic combinations of the above-mentioned conditions with its own intensity of radiation; this also affects the workers' sensitivity to the effects of radiation, which is why the assessment of the effect of radiant energy on workers varies among different authors. Differences are also noted in the sensitivity of the skin to radiation of different spectral composition: rays with a shorter wavelength (e.g., solar) are tolerated more easily. The basis of these differences lies in the different ability of these rays to penetrate deep into body tissues. According to Sonne, red rays of the visible spectrum have the greatest penetrating power. Visible light rays penetrate deep into tissues and are absorbed only there. When accounting for the thermal effect of radiant energy on the worker's body, local effects on the skin, general effects on the entire organism, mainly on thermoregulation, as well as specific effects on the organ of vision are distinguished. In the case of local effects on the skin, we are dealing with the thermal effect of absorbed radiation with all the resulting consequences: an increase in skin temperature, redness, sweating, a sensation of heat at low intensities, which at higher intensities can turn into a painful burning sensation, and then into first and second degree burns with blister formation. There are no photochemical effects, as with the action of ultraviolet rays; the latent period characteristic of the latter is also absent; erythema appears on the skin immediately after exposure and easily disappears if it does not turn into a burn. The skin temperature rises, reaching 38°C and higher during prolonged exposure; with more intense exposure, after the initial heating of the skin, sweating occurs, which lowers its temperature. As a result of repeated exposures, skin pigmentation develops (Ullmann); with exposure lasting for years, chronic skin hyperemia develops, vascular dilations form in individual places, and finally skin atrophy may occur. The question of the development of skin neoplasms as a result of prolonged exposure to radiant energy has not yet been clarified. Observations of the general effect of radiant energy on workers' bodies were conducted mainly under production conditions where it is extremely difficult to isolate its specific effect, since other powerful factors simultaneously act on the worker's body: high ambient temperature and heavy physical labor. This effect is particularly evident in the disruption of thermoregulation, in increased sweating, which sometimes reaches 9-10 liters during an eight-hour working day, with all the resulting consequences of disruption of water-salt balance. The overall load on the cardiovascular system in workers in hot shops in the presence of radiant energy, as a number of observations show, reaches extremely high levels. Thus, Arkadyevsky observed in stokers who cleaned furnaces for 9-26 minutes at a radiation intensity of 5 to 11 calories and with sharp fluctuations in air temperature (from -1.5°C to +28°C), the following phenomena: increased pulse rate to 180-200 beats per minute, respiration to 39-42 per minute; body temperature reached 38-40°C, blood pressure dropped by 20-30 mm; workers complained of dizziness, shortness of breath, palpitations, etc.; skin and sclera became strongly red, the worker was covered in sweat. All these phenomena characteristic of overheating of the body are obviously significantly enhanced under the influence of radiant energy, however, it is difficult to isolate its specific role. The entire meteorological complex of hot shops, uneven heating of individual body surfaces, drafts, etc., create favorable conditions for thermal injuries; under especially unfavorable conditions, heat stroke may occur when the entire body overheats. The effect of radiant energy on the eyes primarily comes from the action of high brightness of radiant energy sources. The cause of the cataract so often described in glassblowers and workers in hot shops has not been precisely established. The origin recognized by most authors from the action of short infrared rays, the so-called Voigt rays, with a wavelength not exceeding 1.5 μ, is disputed by Kraup (see Cataract). To eliminate the harmful effects of radiant energy on the eyes, special protective glasses are used (see). The fight against the harmful effects of radiant energy in production is carried out with measures that help to weaken radiation: shielding its sources, thermal insulation, shields and screens, steam and water curtains; on the worker's body, special clothing and other individual protective devices (gloves, aprons, etc.); or finally, direct cooling of the worker's body surface is used with special blowing ventilation installations (see also Hot shops). The effectiveness of all these measures depends to a large extent on the nature of the other meteorological conditions at the workplace, which is why all measures that help lower the ambient temperature also play a primary role in this struggle. The order of application of protective measures depends in each case on the specific production conditions. Radiant energy in therapy - see Light therapy.

S. Brodsky. N. Rozenbaum.