Chronic Effects of Mercury on Organisms:

Mercury in Modern Urban Conditions


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MERCURY IN MODERN URBAN CONDITIONS Mercury Purification from its adulterants. Removal of mechanical admixtures by filtration through paper filters. Washing in 10 - 20% caustic potash [KOH] or NaOH, to destroy organic contaminants, and the removal of metallic impurities. Washing in distilled water. Oxidizing impurities at high temperature or dissolving them. Heating under reduced pressure. Heating in degassers or fractionators. Mercury in Medical Institutions and in Medical and Biological Laboratories A special risk of chronic mercury effect on working personnel today lies in the wide use of amalgams as a filling material in dental practice. Regarding amalgam carriers, there is presently a link between amalgam weight and urinary mercury content (Z. Goldwater, 1966), although the possibility of the harmful action of mercury, released from the filling, can be considered predominant (S.I. Kozlovskiy, 1965). The technique of preparing fillings from amalgams (heating copper amalgams, grinding the mass during which mercury contacts the air of the premises, etc.) is such that it contains in itself the possibility of contaminating the dental office with mercury vapor. The risk is not only from vapor. In the grinding process and other operations it is possible that the droplets will fall on the work table and the floors and will contaminate fingers and protective clothing with mercury. If slabs containing mercury fulminate admixtures, are prepared incorrectly, they can "spatter" from heat-caused explosion. Additionally under stomato-logical office conditions, as a rule it is unsatisfactory to collect pressed-out mercury. It is better to store it under a layer of water which does not, however, constitute absolute protection of mercury from vaporization. At the same time stamotology offices do not take all necessary measures for improving working conditions. The basic reason for this is insufficient acquaintance of physician stomatologists and administrators of stomatology polyclinics with these facts and with the results of recent observations by hygienists here and abroad. We will discuss some of these. The Yaroslavl Sanitary Epidemicological Station conducted hygienic investigations of dental offices at several walk-in and polyclinics. Air and swab analysis, from office walls, furniture and equipment revealed 0.03 -0.17 mg/m3 mercury concentrations in air, and 0.000064 - 7.5 mg/cm2(swabs). In adjacent locations where no amalgam work was underway, the mercury concentration was 0.005 - 0.04 mg/m3. Copper amalgams made during filling construction were the sources. The walls and furnishings were apparently a secondary depot from which mercury gradually evaporated, entering the air anew. In two persons (a physician and a sanitation worker) who had worked in an environment containing 3-7 times the limit of 0./01 mg/m3, chronic mercury intoxication was diagnosed and they were directed to a therapeutic clinic for treatment. Later five persons in the dental office had a diagnosis of micromercurialism. Later it was observed in fourteen other employees of dental offices in the walk-in clinic. Material analogous in character was obtained by M. M. Gimadeyev (1958) in Kazan. In the air of a dental office at the Municipal Stomatology Polyclinic the author observed mercury vapor in the amalgam preparation area, the adjoining office and seen in the corridor near the surgical office, the office of the head physician. In the plaster walls the mercury content varied between 0.08 - 0.012 mg/100cm2 and in the plaster ceiling between 0.048 - 0.06 mg/100 cm2. M. M. Gimadeyev noticed that during pressing mercury continuously falls on the floor and forms an aggregate which vaporizes continuously, so-called fallow mercury. R. A. Khutoryan's (1961) data showed mercury contamination of nurses' hands who had prepared metal fillings and of physicians at the Kirovograd Regional Hospital. The author's data based on several years of observation of the air in dental offices showed a mercury concentration between 0.03 - 0.17 mg/m3, and in smears from the hands of personnel, 0.003 - 1.35 mg/m3. In the last few years, beginning in 1955, we systematically analyzed the air of dental offices at walk-in polyclinics, stations and several specialized therapeutic institutions, departments of stomatology of medical and post-graduate medical institutes. Analysis of these results showed that the worker respiratory zone in a majority of offices surveyed contained mercury vapor. Only in 9 of the 48 offices studied was no mercury at all detected, in others there were traces. In these 9 offices no amalgams were used or their use was limited to children. Especially interesting is past and present data (1960 - 9163) on the aerial mercury content of a series of offices. There is a trend towards gradual diminution in aerial mercury content in offices of the First Poldol'sk Hospital of Kiev in 1955 was 0.035 - 0.075 mg/m3, while in 1961 mercury was not detected there, although very low concentrations were present (0.004 -0.0055 mg/m3). Sometimes the mercury content of other work zones exceeded permissible limits 5 - 7 times despite attempts at preventing the escape of mercury vapor into the air. Often the presence of drawing devices for filling production necessitated cleaning of floors with a solution of manganese oxide, potassium HC1, washing furniture, windowsills and glass with hot soapy water. The decreased aerial mercury concentration noted by us in 1961 is connected with the organization of a separate office for filling teeth. This office was equipped with an exhaust hood for preparing and storing amalgams and mercury and also with exhaust fans. This measure alone contributed greatly to the reduction of aerial mercury content. Also the Department of Therapeutic Stomatology of the Medical Institute had been in a place not designed for stomatological offices; there were no exhaust hoods where the fillings were prepared. Investigations of the aerial mercury content dynamics indicated that high Hg concentrations persisted for years. Mercury-contaminated items included not only offices where amalgams were prepared and used by adjacent locations, primarily laboratories. Although very small quantities of mercury were detected it was continuously observed in the offices and reagent storage spots. The highest concentrations being detected where mercury and amalgams were kept. Sharp decreases in aerial mercury content was achieved by isolation of amalgam production and storage. 1961 -1963 materials showed that concentrations varied between 0.008 - 0.025 mg/m3. There was a gradual increase in aerial mercury content between the first and second sampling in 7 cases (0.007 -0.01 mg/m3), in 5 only traces were detected and in 12 samples no mercury was detected. Two years later there were negative results in only 5 samples and traces in 2. In the rest the mercury content varied between 0.008 and 0.025 mg/m3. The preceding data shows that the amount of mercury in dental offices is variable not only over the years, but in different months or days. The amount of variation depends on the mercury evaporation intensity (i.e. temperature, air circulation time, presence or absence of ventilation, etc.). However, a specific determining factor is continuous manipulation of copper amalgams in work areas near dental chairs. Dynamic investigations of the air before, at the beginning of the work day, during heating of the copper amalgam and during its use show that during heating the mercury vapor content at the site increased 3 - 5 times. In the course of these and other investigations we established that in offices where more than five doctors worked, 14 - 32 teeth were filled. This agrees with G. G. yaroshenko's data that in the stomatological department of the institute nine doctors filled 27 teeth. Therefore the multiple heating of amalgams makes possible the intensive mercury contamination of the air, the degree of which depends on the volume used. The mercury level of the respiratory zone of dental personnel is usually higher than that in industry. The most striking example of this is that, in one dental office at a Leningrad clinic, where copper amalgam was used, the mercury content was higher than in the plant where it was prepared. Despite the significant difference in mercury volume handled (at the plant, up to 20 - 28 Kg), the industrial mercury concentration was lower than that of the stomatology offices. Conforming facts explain the absence of prolonged attention to the prophylaxis of mercurialism in stomatological practice. It is known that persons working with mercury at industrial enterprises are subject to strict medical surveillance. These persons undergo periodic medical examinations for prolonged periods. Meanwhile, among dental employees, for whom work with mercury is contraindicated there are few. Notwithstanding this fact, there are, although briefly, ill persons in dental offices suffering from one or another oral ailment which renders them especially susceptible to the harmful effects of mercury. Let us remember that mercury is excreted by the mucous glands and often causes mercury-specific gingivitis and stomatitis.