Type: Periodic Element
Periodic Element: (Hg)
RDA: None
Importance- to Body:
Toxic
Distribution- In Body:
Indiscriminant Absorption
Excess Effects:
Symptoms typically include: Sensory impairment (vision, hearing, speech), Disturbed Sensation and a Lack of Coordination. The type and degree of symptoms exhibited depend upon the individual toxin, the dose, and the method and duration of exposure. Case control studies have shown effects such as Tremors, Impaired Cognitive Skills, and Sleep Disturbance in workers with chronic exposure to mercury vapor even at low concentrations in the range 0.7–42 μg/m3. A study has shown that acute exposure (4 – 8 hours) to calculated elemental mercury levels of 1.1 to 44 mg/m3 resulted in Chest pain, Dyspnea, Cough, Hemoptysis, Impairment of Pulmonary Function, and evidence of Interstitial Pneumonitis. Acute exposure to mercury vapor has been shown to result in profound Central Nervous System effects, including Psychotic Reactions characterized by Delirium, Hallucinations, and Suicidal Tendencies. Occupational exposure has resulted in broad-ranging functional disturbance, including Eerethism, Irritability, Excitability, Excessive Shyness, and Insomnia. With continuing exposure, a Fine Tremor develops and may escalate to Violent Muscular Spasms. Tremor initially involves the hands and later spreads to the eyelids, lips, and tongue. Long-term, low-level exposure has been associated with more subtle symptoms of Erethism, including Fatigue, Irritability, Loss of Memory, Vivid Dreams and Depression.
Deficiency Effects:
None listed
Sources Food:
Can be accumulative in Fish
Sources Environmental/Geographic:
Mercury is an extremely rare element in Earth’s crust, having an average crustal abundance by mass of only 0.08 parts per million (ppm). It is found either as a native metal (rare) or in cinnabar, corderoite, livingstonite and other minerals, with cinnabar (HgS) being the most common ore.Mercury ores usually occur in very young orogenic belts where rocks of high density are forced to the crust of Earth, often in hot springs or other volcanic regions
- 65% from stationary combustion, of which coal-fired power plants are the largest aggregate source (40% of U.S. mercury emissions in 1999). This includes power plants fueled with gas where the mercury has not been removed. Emissions from coal combustion are between one and two orders of magnitude higher than emissions from oil combustion, depending on the country.
- 11% from gold production. The three largest point sources for mercury emissions in the U.S. are the three largest gold mines. Hydrogeochemical release of mercury from gold-mine tailings has been accounted as a significant source of atmospheric mercury in eastern Canada.
- 6.8% from non-ferrous metal production, typically smelters.
- 6.4% from cement production.
- 3.0% from waste disposal, including municipal and hazardous waste, crematoria, and sewage sludge incineration.
- 3.0% from caustic soda production.
- 1.4% from pig iron and steel production.
- 1.1% from mercury production, mainly for batteries.
- 2.0% from other sources.
The above percentages are estimates of the global human-caused mercury emissions in 2000, excluding biomass burning, an important source in some regions.
Recent atmospheric mercury contamination in outdoor urban air was measured at 0.01–0.02 µg/m3. A 2001 study measured mercury levels in 12 indoor sites chosen to represent a cross-section of building types, locations and ages in the New York area. This study found mercury concentrations significantly elevated over outdoor concentrations, at a range of 0.0065 – 0.523 μg/m3. The average was 0.069 μg/m3.
Sediments within large urban-industrial estuaries act as an important sink for point source and diffuse mercury pollution within catchments.
Supplemental information:
The World Health Organization, OSHA, and NIOSH all treat mercury as an occupational hazard, and have established specific occupational exposure limits. Environmental releases and disposal of mercury are regulated in the U.S. primarily by the United States Environmental Protection Agency.
Supplemental information: