[34] The first emperor of a unified China, Qín Shǐ Huáng Dì—allegedly buried in a tomb that contained rivers of flowing mercury on a model of the land he ruled, representative of the rivers of China—was reportedly killed by drinking a mercury and powdered jade mixture formulated by Qin alchemists intended as an elixir of immortality.

The equation for this extraction is: In 2020, China was the top producer of mercury, providing 88% of the world output (2200 out of 2500 tonnes), followed by Tajikistan (178 t), Russia (50 t) and Mexico (32 t).

A newspaper claimed that an unidentified European Union directive calling for energy-efficient lightbulbs to be made mandatory by 2012 encouraged China to re-open cinnabar mines to obtain the mercury required for CFL bulb manufacture.

Experiments have failed to unequivocally demonstrate any higher oxidation states: both the claimed 1976 electrosynthesis of an unstable Hg(III) species and 2007 cryogenic isolation of HgF4 have disputed interpretations and remain difficult (if not impossible) to reproduce.

Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore cinnabar and is the brilliant pigment vermilion.

Known as Nessler's reagent, potassium tetraiodomercurate(II) (K2HgI4) is still occasionally used to test for ammonia owing to its tendency to form the deeply colored iodide salt of Millon's base.

A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other applications are slowly being phased out due to health and safety regulations.

Blue mass, a pill or syrup in which mercury is the main ingredient, was prescribed throughout the 19th century for numerous conditions including constipation, depression, child-bearing and toothaches.

The mercury-containing organohalide merbromin (sometimes sold as Mercurochrome) is still widely used but has been banned in some countries, such as the U.S.[72] Mercury is an ingredient in dental amalgams.

[77] In 2003, mercury compounds were found in some over-the-counter drugs, including topical antiseptics, stimulant laxatives, diaper-rash ointment, eye drops, and nasal sprays.

[82] Thermometers containing mercury were invented in the early 18th century by Daniel Gabriel Fahrenheit, though earlier attempts at making temperature-measuring instruments filled with quicksilver had been described in the 1650s.

[84] From the early 21st century onwards, the use of mercury thermometers has been declining, and mercury-containing instruments have been banned in many jurisdictions following the 1998 Protocol on Heavy Metals.

The novel use of mercury permits the creation of compact atomic clocks with low energy requirements ideal for space probes and Mars missions.

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.

[146] A less well-known source of mercury is the burning of joss paper,[147] which is a common tradition practiced in Asia, including China,[148] Vietnam, Hong Kong, Thailand, Taiwan and Malaysia.

[153] Sediments within large urban-industrial estuaries act as an important sink for point source and diffuse mercury pollution within catchments.

[154] The highest mercury concentrations were shown to occur in and around the city of London in association with fine grain muds and high total organic carbon content.

[163][164] New York City residents have been found to be exposed to significant levels of inorganic mercury compounds through the use of skin care products.

Symptoms typically include sensory impairment (vision, hearing, speech), disturbed sensation and a lack of coordination.

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.

[166][167] 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.

[133] 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 tendency.

Occupational exposure has resulted in broad-ranging functional disturbance, including erethism, irritability, excitability, excessive shyness, and insomnia.

Long-term, low-level exposure has been associated with more subtle symptoms of erethism, including fatigue, irritability, loss of memory, vivid dreams and depression.

[173] The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants that need to be controlled to the greatest possible extent.

Thus, industries that release high concentrations of mercury into the environment agreed to install maximum achievable control technologies (MACT).

In March 2005, the EPA promulgated a regulation[174] that added power plants to the list of sources that should be controlled and instituted a national cap and trade system.

The rule was deemed not sufficient to protect the health of persons living near coal-fired power plants, given the negative effects documented in the EPA Study Report to Congress of 1998.

[175] However newer data published in 2015 showed that after introduction of the stricter controls mercury declined sharply, indicating that the Clean Air Act had its intended impact.

The ban applies to new devices only, and contains exemptions for the health care sector and a two-year grace period for manufacturers of barometers.