Toxic Doses and Concentrations.
Data on what concentrations of mercury vapor can lead to chronic intoxication of humans under everyday conditions are contradictory. A. N. L'vov (1939) stated, on the basis of many years of observation, that the effect over the course of a few years of mercury vapor concentrations on the order of (0.04 - 0.05 mg/m3) led to chronic poisoning in a definite number of cases. According to the author, the greatest number of chronic cases occurred at a mercury vapor concentration of 0.03 - 0.05 mg/m3. According to G. F. Gothlin (1911) daily inhalation of from 0.04 -- 1.0 mg Hg for a few months is sufficient to produce chronic poisoning. J. Turner (1924) noted the possibility of mercury poisoning arising from 3-5 hours daily exposure to mercury in 0.771 - 1.285 mg quantities. In his opinion, chronic intoxication can develop within two months after contact with mercury in concentrations > 0.02 mg/m3. According to data of L. Teleky (192), daily inhalation of mercury in concentrations on the order of 0.04 - 0.1 mg/m3 over a few years leads of the development of severe chronic poisoning. K. Lehmann (1919) stated that, during the eight hour working day, air containing an average of 0.15 mg/m3 mercury can produce chronic poisoning. I. Henderson and H. W. Haggard (1930) consider that mercury poisoning develops from daily three to five hour exposure to 0.7 mg/m3 for two to three months. The quantity of mercury ingested daily and causing chronic poisoning, according to: F. Flury's data (1938) is 1 mg; P. Neal (1937) - 0.007 - 0.2 mg/m3; T. Rutherford, A. Johnstone (1942) - more that 0.025 mg/m3; A. Stock (1926) - 0.001 - 0.005 mg/m3. The concentration of metallic mercury and doses of mercury salts producing acute poisoning, also producing chronic intoxication is not exactly determined. N. A. Vigdorchik (1940) states that acute poisoning can arise at concentrations of 1.5 mg/m3. According to O. I. Glazova (1925) lethal intoxication developed upon the inhalation of 2.5 gm of mercury. O. Ya. Mogilevskaya (1947) observed the development of intoxication upon the presence of 5 mg/m3. The author described a case of massive intoxication, when the mercury content of the air of a dormitory was 0.13 - 0.8 mg/m3. Interesting data on toxic doses and concentrations have been obtained in experiments on mammals. A mercury concentration of 16 mg/m3 is lethal to guinea pigs after three day's exposure for two to four hours a day. The toxic concentration for guinea pigs is 0.2 - 0.5 mg/m3 under conditions of daily exposure for four to six hours. Animals continuously exposed to mercury vapor concentrations (up to 8 mg/m3) they died after 35 - 70 days. (Kh. Z. Lyubetskiy, 1953). The lethal concentration for dogs in 20 - 50 mg/m3, after daily eight hour exposures (the animals died within one to three days) and , at 12.5 mg/m3, the animals died after six to sixteen days. At a 3 - b mg/m3 dose, the typical picture of mercury poisoning appeared; at 1.9 mg/m3, no visible signs of intoxication appeared after forty days (A. Fraser, K. Melville, R. Stekie, 1934). Mercury vapor concentrations on the order of 0.015 - 0.1 mg/m3; 0.035 - 0.04 mg/m3 (M. M. Gimadeyev, 1958); 0.02 - 0.05 mg/m3; 0.008 - 0.01 mg/m3; 0.005 - 0.02 mg/m3 (V. N. Kurnosov, 1962) produced in experimental animals (rabbits, cats, white mice) reversible changes in conditioned reflex activity. Other changes of a functional nature were noted at these concentrations. The heterogeneous mercury sensitivity of various animals was established in the course of experiments. White mice, rats and rabbits were most sensitive and guinea pigs less so. The lethal dose of soluble mercury salts upon ingestion by animals is 0.2 - 0.3 gm (M. D. Shvaykova, 1959). Upon intravenous introduction this dose is two times smaller. M. S. Znamenskiy (1949), M. D. Tushinskiy (1939) and other investigators established that the lethal dose was between 0.1 - 0.2 gm of mercuric chloride is toxic and a 0.5 gm dose lethal when taken internally. Mercury nitrate is acutely toxic at higher doses. Acute poisoning by mercury monochloride is possible upon intake of 2 - 3 gm. Concentrations and doses of mercury, producing experimental poisoning in mammals follow: minimal lethal dose of mercury chloride upon introduction into the stomachs of white mice is 0.55 - 0.6 mg/kg (L. U. Medved', 1944). Upon administration by this route to rabbits the lethal dose was 12 mg/kg by the 27 -32nd day from the moment of introduction, while 15 mg/kg - by the 15 - 16th day; 20 -25 mg/kg - by 4 - 11th day, 40 mg/kg in 1 day (P. T. Karavayev, 1939; N. S. Pravdin and S. N. Kremneva, 1939; our data, 1950). The toxic dose of mercury chloride for rabbits was (subcutaneously) 1 - 20 mg/kg, at which intoxication appeared 50 - 90 days from the beginning of the experiment (V. A. Shalimov, 1956); upon introduction into the stomach -- 1 - 8 mg/kg (I M. Trakhtenberg, 1959). |