Exposure to mercury vapor

Elemental mercury in the form of mercury vapor is readily and rapidly absorbed into the bloodstream when inhaled and easily crosses the blood-brain barrier and the placenta. Oral ingestion of elemental mercury is far less hazardous than inhalation of mercury vapor due to its poor absorption in the gut. Acute, high level exposure to mercury vapor can result in respiratory, cardiovascular, neurological, and gastrointestinal effects, and even death. 

Mercury was used to cure the felt used in hats, and workers developed the characteristic signs of mercury vapor toxicity. Acute exposure to high concentrations of mercury vapor causes respiratory distress, which can be fatal. The symptoms of chronic exposure to mercury vapor include personality changes such as excitability, depression, memory loss, fine motor tremor that can become progressively worse, gingivitis, and hallucination. There is some mercury inhalation exposure from dental amalgam, but for most people there are no health-related effects. Metallic mercury is very poorly absorbed from the intestine, thus it is much better to swallow the mercury from a thermometer than inhale it (see chapter on mercury). 

Although the sensor signal is changed during about 30-40 min after exposure to mercury vapor, an estimation of the concentration can be performed from the data measured within the first 5-10 min. 

R. Kishi, R. Doi, Y. Fukuchi, H. Satoh, T. Satoh, A. Ono, et al., Subjective symptoms and neurobehavioral performances of ex-mercury miners at an average of 18 years after the cessation of chronic exposure to mercury vapor. Environ. Res. 62 289, 1993. 

Moszczynski P, Rutowski J, Slowinski S, Bern S, Jakus-Stoga D. Effects of occupational exposure to mercury vapors on T cell and NK-cell populations. Arch Med Res 1996 27(4) 503-7. 

Besides dietary and dental amalgam exposure to mercury compounds, accidental exposure to mercury vapors may occur among the general population (e.g., from breakage of a mercury-containing thermometer), or from use of metallic mercury or mercury containing ointments, creams, and drugs. 

Recent occupational health studies have focused on detecting early effects from mercury on the central nervous system. A dose-response relationship between subjective symptoms and/or impaired performance on psychological tests has been reported [61-64]. It is now conceded that an increased prevalence of neurotic symptoms may occur following long-term exposure to mercury vapor at concentrations exceeding 25 pg/ m [21]. An air concentration of 25 pg/ m roughly corresponds to a urinary excretion of 50 pg Hg/L. 

Ellingsen DG, Efskind J, Berg KJ, Gaarder PI, Thomassen Y. Renal and immunologic markers for chloralkali workers with low exposure to mercury vapor. Scand J Work Environ Health 2000 26(5) 427-35. 

Efskind J, Ellingsen DG, Hartman A, et al. Renal function of chloralkali workers after the cessation of exposure to mercury vapor. Scan J Work Environ Health 2006 32(3) 241 -9. 

The recommended health-based limits are 0.05mgm for occupational exposure, 50pgg creatinine in urine for long-term occupational exposure to mercury vapors, and 1 pgl for exposure by drinking water (WHO report, 1980). 

Mercury is an accumulative poison. Its toxicity depends on its form. Symptoms may start rapidly after acute exposure to high air concentrations of mercury vapor, and can include fever, chills, and nausea. In severe cases (e.g., as a consequence of heating), pulmonary edema may cause death within a few days. Acute exposure to mercury vapor can also produce bronchitis and interstitial pneumonitis. The toxicity of mercuric chloride (i.e., corrosive sublimate) has been well established. Oral ingestion causes severe abdominal cramps, possible ulceration and bleeding of the gastrointestinal tract, and a bloody diarrhea. Loose teeth are noted and hepatitis has been recorded. Nephritis is common if the renal tubes are extensively damaged, it could lead to a... 

Metallic mercury is used in a variety of household products and industrial items, including thermostats, fluorescent light bulbs, barometers, glass thermometers, and some blood pressure devices. The mercury in these devices is contained in glass or metal, and generally does not pose a risk unless the item is damaged or broken, and mercury vapors are released. Spills of metallic mercury from broken thermometers or damaged electrical switches in the home may result in exposure to mercury vapors in indoor air. You must be careful when you handle and dispose of all items in the home that contain metallic mercury. 

For similar exposure routes and forms of mercury, the harmful health effects seen in children are similar to the effects seen in adults. High exposure to mercury vapor causes lung, stomach, and intestinal damage and death due to respiratory failure in severe cases. These effects are similar to those seen in adult groups exposed to inhaled metallic mercury vapors at work. 

In critical periods of development before they are born, and in the early months after birth, children and fetuses are particularly sensitive to the harmful effects of metallic mercury and methylmercury on the nervous system. Harmful developmental effects may occur when a pregnant woman is exposed to metallic mercury and some of the mercury is transferred into her developing child. Thus, women who are normally exposed to mercury vapors in the workplace (such as those working in thermometer/barometer or fluorescent light manufacturing or the chlor-alkali industry) should take measures to avoid mercury vapor exposures during pregnancy. Exposures to mercury vapors are relatively rare outside of the workplace, unless metallic mercury is present in the home. 

Similarly, an elevated white cell count was observed in a 12-year-old girl with a 6-month exposure to mercury vapors from a spill of metallic mercury in her home (Fagala and Wigg 1992). Thrombocytopenia and frequent nosebleeds were reported in two of four family members exposed to mercury... 

A case study reporting neurological effects in a boy after exposure to mercury vapor released from paint containing phenylmercuric acetate (Aronow et al. 1990) was discussed under metallic mercury because the exposure was to metallic mercury vapors released from the paint. 

After exposure to mercury vapor, mercury is distributed throughout the body in different chemical and physical states. Metallic mercury dissolves in the blood upon inhalation, and some remains unchanged (Magos 1967). Metallic mercury in the blood is oxidized to its divalent form in the red blood cells (Halbach and Clarkson 1978). The divalent cation exists as a diffusible or nondiffusible form. The nondiffusible form is mercuric ions that bind to protein and are held in high-molecular weight complexes, existing in equilibrium with the diffusible form. 

Absorbed metallic mercury crosses the placenta, and the fetal blood may concentrate mercury to levels 10 or more times the levels found in the maternal blood. Therefore, the developing fetal nervous system may be quite sensitive to maternal exposures to mercury vapors. 

Studies assessing mercury vapor exposure have suggested various ratios relating the concentration of mercury in the air (in g/m3) to the levels of mercury in the urine (in g/L). Such estimates include 1 1 (Bell et al. 1973), 1 1.22 (Roels et al. 1987), and 1 2.5 (Lindstedt et al. 1979 Rosenman et al. 1986). Urinary metallic mercury levels ranging from 0.05 to 1.7 g/L were detected in the urine of workers exposed to mercury vapor (>0.1 mg/m3) this elemental mercury represented <1% of the inorganic mercury content of the urine (Y oshida and Yamamura 1982). With increased exposure to mercury vapor (0.47-0.67 mg/m3), the amount of elemental mercury in the urine increased. A "rough" correlation between levels of metallic mercury vapor in air and mercury levels in blood and urine was established by Rosenman et al. (1986). They associated levels of 50 g/100 mL in blood and 250 g/L in urine with a mercury level in air of approximately 0.1 mg/m3 (8-hour TWA), and 28 g/100 mL in blood and 100 g/L in urine with a TWA of 0.05 mg/m3. Roels et al. (1987) found a correlation between daily mercury vapor exposure and blood or urine mercury levels in 10 workers employed for at least 1 year at an alkaline battery plant. The mercury levels in the air and the pre- or post-workshift levels of blood and urinary mercury correlated well (r=0.79-0.86 [blood] and r=0.70-0.80 [urine]). Based on a ratio of... 

Thus, expired air as a measure of mercury exposure can only be used soon after short-term exposure to mercury vapor. There is no information on the amount of mercury in expired air following long-term exposure to mercury. 

Case studies have associated exposure to mercury vapor with neurological effects (e.g., tremors, insomnia, shyness, emotional instability, decreased motor function and muscle reflexes, headaches, and abnormal EEGs) (Davis et al. 1974 Jaffe et al. 1983 McFarland and Reigel 1978). Some studies have examined the relationship between nerve function and mercury levels in blood, urine, and tissue. Tissue levels of mercury have also been found to correlate with impaired nerve function. Among 23 dentists with mercury levels greater than 20 g/g (measured in wrist tissue), 30% exhibited reduced nerve conduction velocity when compared with dentists with tissue levels of mercury below 20 g/g (Shapiro et al. 1982). The decrease in nerve conduction velocity was observed in both sensory and motor nerves. 

Barregard L, Hogstedt B, Schutz A, et al. 1991. Effects of occupational exposure to mercury vapor on lymphocyte micronuclei. Scand J Work Environ Health 17(4) 263-268. 

Berlin M, Jerksell LG, von Ubisch H. 1966. Uptake and retention of mercury in the mouse brain—a comparison of exposure to mercury vapor and intravenous injection of mercuric salt. Arch Environ Health 12 33-42. 

King G. 1954. Acute pneumonitis due to accidental exposure to mercury vapor. Ariz Med 11 335. 

Moszczynski P, Bern S, Moszczynski P Jr, et al. 1990a. The indices of immunity and acute phase reaction according to duration of exposure to mercury vapors in men. Med Pr 41(3) 169-174. (Polish)... 

Newland MC, Warfvinge K, Berlin M. 1996. Behavioral consequences of in utero exposure to mercury vapor alterations in lever-press durations and learning in squirrel monkeys. Toxicol Appl Pharmacol... 

Piikivi L, Hanninen H, Martelin T, et al. 1984. Psychological performance and long term exposure to mercury vapors. Scand J Work Environ Health 10 35-41. 

Schionning JD, Poulsen EH, Moller-Madsen B, et al. 1991. Ultrastructural localization of mercury in rat dorsal root ganglia after exposure to mercury vapor. In Graumann W, ed. Progress in histochemistry and cytochemistry, vol. 23, No. 1-4 Histo-and cytochemistry as a tool in environmental toxicology. 

Stopford W, Bundy SD, Goldwater LJ, et al. 1978. Microenvironmental exposure to mercury vapor. 

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