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MERCURY VAPOR

BACKGROUND INFORMATION

PHYSICAL AND CHEMICAL PROERTIES

Structural formula:

Hg

Molecular weight:

200.59

Synonyms:

Quicksilver

CAS number:

7439–97–6

Physical state:

A silver-white, heavy, liquid metal, which is slightly volatile at ordinary temperatures

Vapor pressure:

2×10−3 mm

Specific gravity:

13.59

OCCURRENCE AND USE

Mercury has many uses besides its well-known use in thermometers, barometers, and manometers. It is used in arc lamps, switches, and fungicides. Gold extraction and other industrial applications use mercury (Windholz et al., 1976; ACGIH, 1980). It is a component of submarine atmospheres and some solid-fuel rocket propellants.

SUMMARY OF TOXICITY INFORMATION

EFFECTS ON HUMANS

Acute toxicity of mercury is characterized by nausea, vomiting, abdominal pain, bronchitis, bloody diarrhea, and anuria with uremia. (Windholz et al., 1976; ACGIH, 1980) Chronic toxicity is characterized by tremors, weakness, sensory abnormalities, memory loss, erethism, muscle pains, gingivitis, emotion or intellect changes, and kidney damage (Browning, 1969).

Milne et al. (1970) reported that four workmen became ill for a few days to a month after exposure to a mercury-contaminated atmosphere for 2.5, 4, and 5 h. Mercury concentrations ranged from 1.1 to 2.9 mg/m3. Popsecu et al. (1979) claimed that workers exposed for over a year to an atmosphere containing mercury at 0.15–0.44 mg/m3 in a chemical plant suffered no apparent mercury poisoning. Their urinary mercury excretion was 890 g/L. Smith et al. (1971) evaluated blood mercury and urinary excretion of mercury in 1000 workers chronically exposed to elementary mercury in the workplace 40 h/wk. He reported that symptoms of mercury poisoning were seen when the concentration in the atmosphere exceeded 0.1 mg/m3. This confirmed earlier work reported by Neal et al. (1941). Friberg (1951) and Seifert and Neudert (1954) reported that mercury poisoning occurred when concentrations remained around 0.1 mg/m3.

Smith’s data on blood and urinary mercury concentrations follow:



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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 MERCURY VAPOR BACKGROUND INFORMATION PHYSICAL AND CHEMICAL PROERTIES Structural formula: Hg Molecular weight: 200.59 Synonyms: Quicksilver CAS number: 7439–97–6 Physical state: A silver-white, heavy, liquid metal, which is slightly volatile at ordinary temperatures Vapor pressure: 2×10−3 mm Specific gravity: 13.59 OCCURRENCE AND USE Mercury has many uses besides its well-known use in thermometers, barometers, and manometers. It is used in arc lamps, switches, and fungicides. Gold extraction and other industrial applications use mercury (Windholz et al., 1976; ACGIH, 1980). It is a component of submarine atmospheres and some solid-fuel rocket propellants. SUMMARY OF TOXICITY INFORMATION EFFECTS ON HUMANS Acute toxicity of mercury is characterized by nausea, vomiting, abdominal pain, bronchitis, bloody diarrhea, and anuria with uremia. (Windholz et al., 1976; ACGIH, 1980) Chronic toxicity is characterized by tremors, weakness, sensory abnormalities, memory loss, erethism, muscle pains, gingivitis, emotion or intellect changes, and kidney damage (Browning, 1969). Milne et al. (1970) reported that four workmen became ill for a few days to a month after exposure to a mercury-contaminated atmosphere for 2.5, 4, and 5 h. Mercury concentrations ranged from 1.1 to 2.9 mg/m3. Popsecu et al. (1979) claimed that workers exposed for over a year to an atmosphere containing mercury at 0.15–0.44 mg/m3 in a chemical plant suffered no apparent mercury poisoning. Their urinary mercury excretion was 890 g/L. Smith et al. (1971) evaluated blood mercury and urinary excretion of mercury in 1000 workers chronically exposed to elementary mercury in the workplace 40 h/wk. He reported that symptoms of mercury poisoning were seen when the concentration in the atmosphere exceeded 0.1 mg/m3. This confirmed earlier work reported by Neal et al. (1941). Friberg (1951) and Seifert and Neudert (1954) reported that mercury poisoning occurred when concentrations remained around 0.1 mg/m3. Smith’s data on blood and urinary mercury concentrations follow:

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 Mercury concentration in air, mg/m3 Mercury in Blood μg/100 ml Mercury in Urine, μg/L 0.1 6 260 0.025 2.5 100 These can be compared to normal values of 0.8 μg/100 ml in blood (Study Group on Mercury Hazards, 1971) and 8 μg/L in urine (Solloman, 1957). Lauwerys and Buchet (1973) reported on 40 chemical and biologic workers chronically exposed to mercury vapors and 23 biologic technicians who had not been exposed (controls). The data are summarized below. No. Mercury Conc., mg/m3 Mercury in Blood, μg/100 ml Mercury in Urine, μg/g of creatinine RBC-ChE, % of control 23 0 0.65 2.3 100 32 0.04 0.96 7.5 94 8 0.04 1.2 23.5 80 Increased plasma galactosidase and plasma catalase activities were also detected. Factory workers exposed to elemental mercury (in a mercury cell chlorine plant) were found to have ulnar nerve conduction deficits when their urinary excretion of mercury exceeded 250 μg/L, despite the fact that they were asymptomatic and appeared normal when examined by an industrial physician (Levine et al. 1982). Other mercury studies are reported in Threshold Limit Values (ACGIH, 1980). There is no evidence that exposure to mercury leads to excess cancer mortality in humans (Woo and Arcos, 1981). EFFECTS ON ANIMALS Acute Toxicity Rabbits exposed for 4 h to saturated vapors of mercury (27 mg/m3) suffered severe poisoning of brain, colon, heart, liver, lungs, and kidneys (Ashe et al. 1953). The rat oral LD50 of HgCl2 is 210 mg/kg. Subacute Toxicity Guinea pigs exposed 10 h/d for 4 d to mercury vapor at 6 mg/m3 developed neurotic effects and hemorrhagic colitis. Mercury was stored in the kidneys (Holzmann, 1931). Chronic Toxicity Dogs, rabbits, and rats showed no effects when exposed to mercury vapor at 0.1 mg/m3 for 83 wk (Fraser et al., 1934)

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 Carcinogenicity There does not appear to be any useful animal information on carcinogenic hazards of exposure to mercury. INHALATION EXPOSURE LIMITS An international committee chaired by Lars Friberg met in 1968 (Report of an International Committee, 1969) to consider threshold limit values for occupational exposure to mercury. Goldwater pointed out that in the study conducted by Neal et al. (1941), on which the current standard for inorganic mercury depended, cases of mercurialism occurred at 0.1 mg/m3 and at all higher concentrations and that the use of 0.1 mg/m3 as a standard was therefore not proper, because it allowed no safety factor. Some studies conducted since then have suggested that 0.1 mg/m3 is adequate; others have found occasional cases of toxicity at lower concentrations. For example, Smith et al. (1971) found no significant incidence of effects at 0.1 mg/m3; these authors, however, also agreed that the use of that concentration as a TLV allowed no safety factor. Friberg quoted examples of mercury poisoning at concentrations around 0.1 mg/m3 (Friberg, 1951; Seifert and Neudert, 1954). As a result, the ACGIH TLV-TWA for inorganic mercury, originally set at 0.1 mg/m3, was reduced to 0.05 mg/m3 in 1971. Biologic changes may occur in persons exposed to mercury vapor at concentrations below the current TLV (Lauwerys and Buchet, 1973). There appears to be an increase in the concentration of mercury in the blood and urine, with a concomitant slight decrease in RBC cholinesterase activity and increase in plasma galactosidase and plasma catalase activities. There is no evidence that these abnormalities have any health implications, but they may be useful in surveillance of exposed persons. On the basis of Swedish experience, a TLV of 0.01 mg/m3 for alkyl mercury compounds was suggested by ACGIH in 1948. Despite the lack of evidence of mercury poisoning between 0.01 and 0.1 mg/m3, this TLV recommendation has been retained. Because of the greater toxicity of organic mercurials, occupational TLVs of 0.05 mg/m3 for inorganic and 0.01 mg/m3 for organic mercury seem reasonable (ACGIH, 1980). NIOSH recommended that the permissible exposure limit for inorganic mercury in the workplace be set at 0.05 mg/m3 in 1973. A 24-h EEL of 0.001 mg/m3 was recommended to NASA in 1979 (Katz, 1979). COMMITTEE RECOMMENDATIONS EXPOSURE LIMITS In 1966, the Committee recommended a 24-h EEL of 2.0 mg/m3 and a 90-d CEL of 0.01 mg/m3 for mercury. The data of Milne et al. (1970) suggest that a 24-h EEL should be below 1.1 mg/m3. The data of Popescu et al. (1979) show that, although long-term exposure at 0.44 mg/m3 produced no apparent mercury poisoning, urinary and blood contents were increased and

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 showed accumulation of mercury. This and other long-term exposure studies among workers (8-h workday) suggest that a 24-h continuous exposure at 0.2 mg/m3 could be tolerated without ill effects. The EEl recommended by Katz (1979) of 0.001 mg/m3 appears to be exceedingly cautious, and the 1966 recommendation of this Committee (2.0 mg/m3) appears somewhat high. The Committee believes that a 24-h EEL of 0.2 mg/m3 is supported by the data on humans cited here and recommends this exposure limit. The long-term exposure results of Smith (1972), Popescu et al. (1979), and Lauwerys and Buchet (1973) support retention of the 1966 recommendation for a 90-d CEL of 0.01 mg/m3. To summarize, the Committee recommends the following exposure limits for mercury vapor: 24-h EEL: 0.2 mg/m3 90-d CEL: 0.01 mg/m3

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 REFERENCES American Conference of Governmental Industrial Hygienists. 1980. Documentation of the Threshold Limit Values. 4th ed. Cincinnati, OH.: American Conference of Governmental Industrial Hygienists. p. 254–256. Ashe, W.F., Largent, E.H., Dutra, F.F., Hubbard, D.M., and Blackstone, M. 1953. Behavior of mercury in the animal organism following inhalation. AMA Arch. Ind. Hyg. Occup. Med. 7:19–43. Browning, E. 1969. Toxicity of Industrial Metals. 2nd ed. New York: Appleton-Century-Crofts. [383 p.] Fraser, A.M., Melville, K.I., and Stehle, R.L. 1934. Mercury-laden air: The toxic concentration. The proportion absorbed and the urinary excretion. J. Ind. Hyg. 16:77–91. [Chem. Abs. 28:2787, 1934] Friberg, L. 1951. Chronic poisoning with inorganic mercury compounds. Nord. Hyg. Tidskr. 32:240–249. [Chem. Abs. 48:12312e, 1954] Holtzmann, 1931. The retention of mercury by the body. Arch. Hyg. 106:377–380. [Chem. Abs. 26:3844, 1932] Katz, S. 1979. Aerospace operations criteria for mercury thresholds. Chicago: IIT Research Institute. [69 p.] Lauwerys, R.R., and Buchet, J.P. 1973. Occupational exposure to mercury vapors and biological action. Arch. Environ. Health 27:65–68. Levine, S.P., Cavender, G.D., Langolf, G.D., and Albers, J.W. 1982. Elemental mercury exposure: Peripheral neurotoxicity. Br. J. Ind. Med. 39:136–139. Milne, J., Christophers, A., and de Silva, P. 1970. Acute mercurial pneumonitis. Br. J. Ind. Med. 27:334–338. Neal, P.A., Flinn, R.H., Edwards, T.I., and Reinhart, W.H., et al. 1941. Mercurialism and its control in the felt-hat industry. U.S. Public Health Service Public Health Bulletin, 263. Popescu, H.I., Negru, L., and Lancranjan, I. 1979. Chromosome aberrations induced by occpational exposure to mercury. Arch. Environ. Health 34:461–463.

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Emergency and Continuous Exposure Limits for Selected Airborne Contaminants, Volume 1 Report of an International Committee. Friberg, L., Chairman. 1969. Maximum allowable concentrations of mercury compounds. Ach. Environ. Health 19:891–905. Seifert, P., and Neudert, H. 1954. The question of occupational mercury poisoning. Zentralbl. Arbeitsmed. Arbeitsschutz. 4:129–137. Smith, R.G., Hermann, W., Mooney, T.F., and Patil, L.J. 1971. The effects of chronic exposure to mercury vapor. Am. Ind. Hyg. Assoc. J. 32:68, abstr. no. 169. Smith, R.G. 1972. Dose-response relationship associated with known mercury absorption at low dose levels of inorganic mercury. In R. Hartung, and B.D.Dinman, eds. Environmental Mercury Contamination. Ann Arbor, MI: Ann Arbor Science, p. 207–222. Sollmann, T. 1957. A Manual of Pharmacology and Its Applicaton to Therapeutics and Toxicology. 8th ed. Phila.: W.B.Saunders. p. 1314–1319. Study Group on Mercury Hazards. Nelson, N., Chairman. 1971. Hazards of Mercury: Special Report to the Secretary’s Pesticide Advisory Committee, Department of Health, Education, and Welfare, November 1970. Environ. Res. 4:1–69. Windholz, M., Budavari, S., Stroumtsos, L.Y., and Fertig, M.N., eds. 1976. The Merck Index: An Encyclopedia of Chemicals and Drugs. 9th ed. Rahway, NJ: Merck & Co. p. 766–767. Woo, Y.-T., and Arcos, J.C. 1981. Environmental Chemicals. In J.M. Sontag, ed. Carcinogens in Industry and the Environment. New York: Marcel Decker, p. 167–281.