Pitch

Pitch, sometimes also called coal tar pitch, is the final product of the distillation of coal tar. Pitch finds very extensive and diverse application both in its unmodified form (creating waterproof or acid-resistant surfaces in reservoirs, foundations, etc.) and in mixture with other substances and solvents (briquetting, wood impregnation, production of roofing felt, coating of electrodes, production of axle grease, lacquers for covering iron structures and pipes, preparation of insulating materials, artificial asphalt, etc.). Upon contact with P., its dust, vapors, or products containing it, workers experience a series of pathological phenomena. Most frequently affected are workers at coke benzene plants (see Coke Benzole Production), engaged in direct manipulation with P. during its extraction, especially the breaking up of solidified P. in reservoirs and its subsequent loading into cars. There have also been mass diseases among railroad and other transport workers (mainly loaders) who came into contact with P. during its transportation, transshipment in ports to ships, etc. Pitch causes occupational diseases also in workers at roofing felt plants, briquette factories, and metallurgical enterprises [when painting cast-iron pipes (blackers), large iron structures and their further transportation]. P. is a mixture of products with different properties, physical and chemical. Differences in the technological process of obtaining P. are therefore also reflected in the degree of its photodynamic activity. The earliest phenomena occurring in workers within the first day, and sometimes even hours, after contact with P. consist of painful inflammation of the skin of open parts of the body (face, neck, hands, etc.) and open mucous membranes and inflammation of the conjunctiva with pronounced photophobia. Particularly characteristic is the sharp border of inflammation on the parts of the body covered by clothing. General disturbances and increased body temperature are observed. From the moment of exposure to P. until the onset of the disease, there is always a certain latent period, although sometimes obscured by the work continuing for several hours or transient skin irritation due to the irritating effect of certain components of P. Another characteristic phenomenon, often noted by victims, is the appearance of lesions only after washing off the particles of P. covering the skin. Finally, patients note the undeniable influence of irradiation of the affected areas by direct sunlight, causing a burning sensation and intensification of the inflammatory phenomena that had already begun to subside. In general, the picture of the lesion completely resembles a sunburn. Acute inflammation of the skin after a certain time turns into peeling and ends with pigmentation, which with repeated lesions sometimes reaches very great intensity, characteristic of pitch workers. In the further course, recurrences of inflammation are sometimes observed under the influence of insolation alone, which practically makes workers unable to work for quite significant periods. With further contact with P., some workers develop varying degrees of habituation, so that the pathological phenomena are limited to slight itching, peeling, and pigmentation. Some authors point to irritation of the upper respiratory tract, ulcers of the nasal mucosa, and even diseases of the middle ear (Krukovery), occurring with prolonged exposure to P. For cases of longer exposure to P., acne, pustules, and furuncles spreading all over the body, face, and forearms are most characteristic; they are remarkably persistent, sometimes stopping only after cessation of work with P. A comparatively harmless consequence of chronic exposure to P. is atrophy of the skin with disturbances of pigmentation and the formation of telangiectases. Finally, the most serious consequence of prolonged work with P. should be considered skin neoplasms, initially benign in nature, in the form of hyperkeratoses, warts, and then malignantly degenerating. Clinically, pitch cancer, occasionally occurring in very young subjects, in most cases represents a carcinoma with a relatively benign course, rarely giving metastases and well amenable to surgical treatment. This whole diverse picture of diseases in workers dealing with P. and its products for a long time presented great difficulties for explanation. At the present time, the mechanism of action of P. has been sufficiently clarified (A. S. Guillaume). It is considered the result of the property inherent in P. and other photodynamic substances to cause the phenomenon of photosensitization. The photodynamic nature of these substances is connected with their common property of fluorescence in the rays of the visible part of the solar spectrum, with a wavelength from 400 to 800 mμ. Visible rays of light, not possessing under ordinary conditions the ability to photochemical reactions, due to the process of fluorescence acquire such a property, quite analogous to the action of ultraviolet rays. For the manifestation of a photochemical reaction on human skin when irradiated by visible light, an indispensable condition is the impregnation of the cells of the Malpighian layer with particles of a photodynamic substance capable of fluorescence when irradiated by these rays. The mechanism of the origin of pitch diseases and the decisive role in these processes of the visible part of the spectrum determine the nature of preventive measures. They must have as their task, on the one hand, to prevent the entry of P. and its components onto the skin and into the worker's body, and on the other hand, to protect his skin from the action of light rays. The most radical measures must be recognized as those in which the worker is completely eliminated from contact during work with P., its dust, vapors, etc. (hermetization and mechanization of production processes, packaging, especially during the transshipment and transport of P. or objects coated with P.). Special clothing coming into contact with P. should be made of dense dust-proof fabric and fit tightly (especially for women). To protect the eyes, tightly fitting the orbit glasses (in leather or rubber frames) are used. When working under direct sunlight, hoods with an eye slit or fabric masks are used. To protect the skin of open parts of the body from the entry of P. and the action of sunlight, the abundant application of protective ointments, pastes before starting work, including clay, is also successfully used. Conducting work with P. only at night can have practical significance only in very narrow limits, and does not eliminate the need to apply the above protective measures. S. Brodsky.