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University of Toronto Scarborough
Environmental Science
Jovan Stefanovic

Chapter 4: Human Health and Heavy Metals Exposure N Metals, a major category of globally distributed pollutants, are natural elements that have been extracted from the earth and harnessed from human industry and products for millennia N Metals are notable for their wide environmental dispersion from such activity; N Their tendency to accumulate in select tissues of the body N Their overall potential to be toxic even at relatively minor levels of exposure o In case of lead and mercury, may be toxic even at trace levels of exposure N Even metals that are essential have the potential to become harmful at high levels of exposure, a reflection of a basic tenet of toxiocology 9K04802,N089K054L843 N US. Agency for Toxic Substances and Disease Registry (ATSDR) o Rankings of metals as potential hazards The first, second, third, and sixth hazards are heavy metals: lead, mercury, arsenic, and cadmium N Exposure to metals can occur through a variety of routes o Metals may be inhaled as dust or fume Tiny particulate matter, such as the lead oxide particles produced by the combustion of leaded gasoline) o Some can be vaporized and inhaled o Metals may also be ingested involuntarily through food and drink Amount absorbed from the digestive tract can vary widely, depending on the chemical form of the metal and the age and nutritional status of the individual o Once a metal is absorbed, it distributes in tissues and organs Metals tend to persist in some storage sites, like the liver, bones, and kidneys, for years or decades N Toxicity of metals most commonly involves the brain and the kidney, but other manifestations occur, and some metals, such as arsenic are clearly capable of causing cancer N Difficult in diagnosis o Because an individual with metals toxicity, even if high dose and acute, typically has very general symptoms such as weakness or headache N Chronic Exposure to metals at a high enough level to cause chronic toxicity effects o Such as hypertension in individuals exposed to lead and renal toxicity in individuals exposed to cadmium Mercury N Mercury comes in a number of different chemical forms N Metallic mercury (Hg) is used in thermometers, dental amalgams, and some batteries Exposure N In its pure form, metallic mercury is a liquid, N Contrary to popular opinion, it is not hazardous if ingested (because it is not significantly
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