Harmful effects of mercury compounds. Manufacture of paints, various household items, and pesticides uses mercury; the finished product and the waste products released into air and water may contain mercury. The aquatic food chain can concentrate organic mercury compounds in fish and seafood, which, if eaten by humans, can affect the central nervous system, impairing muscle, vision, and cerebral function, leading to paralysis and sometimes death (see Minamata disease). Acute mercury poisoning causes severe digestive-tract inflammation. Mercury accumulates in the kidneys, causing uremia and death. Chronic poisoning, from occupational inhalation or skin absorption, causes metallic taste, oral inflammation, blue gum line, extremity pain and tremor, weight loss, and mental changes (depression and withdrawal). Drugs containing mercury can cause sensitivity reactions, sometimes fatal. In young children, acrodynia (pink disease) is probably caused by an organic mercury compound in house paints.
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Metallic chemical element, chemical symbol Hg, atomic number 80. Mercury is the only elemental metal that is liquid at ordinary temperatures, with a freezing point of −38 °F (−39 °C) and a boiling point of 674 °F (356.9 °C). Silvery white, dense, toxic (see mercury poisoning), and a good conductor of electricity, mercury is occasionally found free in nature but usually occurs as the red sulfide ore, cinnabar (HgS). It has many uses—in dental and industrial amalgams, as a catalyst, in electrical and measuring apparatus and instruments (e.g., thermometers), as the cathode in electrolytic cells, in mercury-vapour lamps, and as a coolant and neutron absorber in nuclear power plants. Many of mercury's compounds, in which it has valence 1 or 2, are pigments, pesticides, and medicinals. It is a dangerous pollutant because it concentrates in animal tissues in increasing amounts up the food chain.
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First series of U.S. manned spaceflights (1961–63), which began about three weeks after Yury A. Gagarin became the first human in space. In May 1961 Alan B. Shepard rode the first Mercury space capsule, Freedom 7, on a 15-minute, 302-mi (486-km) suborbital flight, attaining a maximum altitude of 116 mi (186 km). The first U.S. manned flight in orbit was that of the Friendship 7, carrying John H. Glenn, Jr., in February 1962; it completed three orbits. The last Mercury flight, Faith 7, launched in May 1963, was the longest, making 22 orbits in about 34 hours.
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