A toxic heavy metal is a relatively solid metal or metaloid known for its potential toxicity, especially in an environmental context. The term has special applications for cadmium, mercury, lead and arsenic, all of which appear in the list of 10 worldly chemicals of public concern. Other examples include manganese, chromium, cobalt, nickel, copper, zinc, selenium, silver, antimony and thallium.
Heavy metals are found naturally on earth. They become concentrated as a result of human-induced activities and can enter plants, animals, and human tissues through inhalation, diet, and manual handling. Then, they can bind and interfere with the function of vital cellular components. The effects of toxic arsenic, mercury, and lead are known to people of antiquity, but the methodical studies of the toxicity of some heavy metals emerged from 1868. In humans, heavy metal poisoning is generally handled by the administration of chelating agents. Some elements that are considered toxic heavy metals are very important, in small quantities, for human health.
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Source of contamination
Heavy metals are found naturally on earth, and become concentrated as a result of human-caused activities. Common sources come from mining and industrial waste; vehicle emissions; lead-acid batteries; fertilizer; paint; treated wood; aging water supply infrastructure; and microplastic floating in the world's oceans. Arsenic, cadmium and lead can be present in children's toys at levels that exceed the regulatory standards. Lead can be used in toys as stabilizers, color enhancers, or anti-corrosive agents. Cadmium is sometimes used as a stabilizer, or to increase the mass and luster of toy jewelry. Arsenic is considered used in connection with dye dyes. Regular alcoholic distillation of illegal flutes may be exposed to arsenic or lead poisoning whose source is arsenic contaminated lead used for soldering distillation apparatus. Rat toxins used in grain and mashed stores may be another source of arsenic.
Lead is the most common heavy metal contaminant. As a component of tetraethyl lead, (CH
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4 Pb , used extensively in gasoline during the 1930s 1970s. The lead level in the aquatic environment of industrial societies has been estimated to be two to three times that of the pre-industrial level. Although the use of leaded gasoline was largely removed in North America in 1996, land beside roads built prior to this time maintained a high concentration of lead. Lead (from tin (II) azide or tin styphnate used in firearms) gradually accumulates at the firearms training site, pollutes the local environment and exposes various employees to the risk of lead poisoning.
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Heavy metals enter the tissues of plants, animals and humans through air breathing, diet and manual handling. Motor vehicle emissions are a major source of airborne contaminants including arsenic, cadmium, cobalt, nickel, lead, antimony, vanadium, zinc, platinum, palladium and rhodium. Water sources (groundwater, lakes, rivers and streams) can be contaminated by heavy metal washing of industrial and consumer waste; acid rain can aggravate this process by releasing heavy metals trapped in the soil. Plants are exposed to heavy metals through water uptake; animals eat this plant; consumption of plant and animal foods is the largest source of heavy metals in humans. Skin absorption, for example from contact with soil, or toys and metallic jewelry, is another potential source of heavy metal contamination. Toxic heavy metal can accumulate in organisms because it is difficult to metabolize.
Destructive effects
Heavy metals "can bind to vital cellular components, such as structural proteins, enzymes, and nucleic acids, and disrupt their function". Symptoms and effects may vary according to metal or metal compound, and the dose involved. Broadly, long-term exposure to toxic heavy metals can have a carcinogenic, central and peripheral nervous system and circulatory effects. For humans, a typical presentation related to exposure to one of the "classic" toxic heavy metals, or chromium (other toxic heavy metals) or arsenic (a metalloid), is shown in the table.
History
The effects of arsenic, mercury and lead poison were known by ancient people but the methodical studies on the overall toxicity of heavy metals emerged from 1868. In that year, Wanklyn and Chapman speculated on the adverse effects of heavy metal arsenic, tin, copper, zinc, iron and manganese "in drinking water They recorded" lack of investigation "and were reduced to" requested requests for data collection. "In 1884, Blake described a clear relationship between toxicity and the weight of elemental atoms The following sections provide historical thumbnails for toxic heavy metals "classic" (arsenic, mercury and lead) and some more recent examples (chromium and cadmium).
Arsenic
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Mercury
China's first emperor united, Qin Shi Huang, reportedly, died of swallowing mercury pills intended to give him eternal life. The phrase "mad as a prostitute" may be a reference to mercury poisoning among mills (called "mad crazy disease"), since mercury-based compounds were once used in the manufacture of felt caps in the 18th and 19th centuries. Historically, gold amalgam mercury) is widely used in plating, which causes many casualties among workers. It is estimated that during the construction of the Saint Isaac Cathedral alone, 60 workers died from suctioning the main dome. Outbreaks of methylmercury poisoning occurred in several places in Japan during the 1950s due to the release of the mercury industry into rivers and coastal waters. The most famous examples are in Minamata and Niigata. In Minamata alone, more than 600 people died from what is known as Minamata disease. More than 21,000 people filed claims with the Japanese government, of which nearly 3000 became certified as having the disease. In 22 documented cases, pregnant women who consumed contaminated fish showed mild or asymptomatic symptoms but gave birth to infants with severe developmental disabilities. Since the Industrial Revolution, the level of mercury has tripled in many ocean layers near sea level, especially around Iceland and Antarctica.
Lead
Side effects of tin are known by the ancients. In the 2nd century BC, the Greek botanist, Nicander described colic and paralysis seen in people who are lead poisoning. Dioscorides, a Greek physician who was considered to have lived in the 1st century, wrote that leading "made the mind give way". Lead is used extensively in Roman waterways from about 500 BC to 300 AD. Engineer Julius Caesar, Vitruvius, reported, "the water is much healthier than the pottery pipe than the lead pipe, so it seems to be made wound by lead, because white lead is produced by it, and it is said to be harmful to humans. During the Mongol period in China (1271-1368 AD), tin pollution due to silver smelting in the Yunnan region exceeded the contamination level of modern mining activity almost four times. In the 17th and 18th centuries, people in Devon were struck by a condition known as Devonian colic; this is found due to the exploitation of lead-contaminated juice. In 2013, the World Health Organization estimates that lead poisoning generates 143,000 deaths, and "contributes [d] to 600,000 new cases of children with intellectual disabilities", every year. In the US city of Flint, Michigan, lead contamination in drinking water has been a problem since 2014. The source of the contamination has been linked to "corrosion in lead and iron pipes that distribute water to city dwellers". By 2015, the level of drinking water lead in northeast Tasmania, Australia, is reported to be more than 50 times the national drinking water guidelines. The source of the contamination was associated with "a combination of dilapidated drinking water infrastructure, including head jointed pipes, end-of-life polyvinyl chloride pipes and household pipes".
Chromium
The chromium (III) compounds and chromium metal are not considered a health hazard, while the toxicity and carcinogenic properties of chromium (VI) have been known at least since the late 19th century. In 1890, Newman described an increased risk of cancer workers in chromate dye companies. Chromate-induced dermatitis was reported to aircraft workers during World War II. In 1963, dermatitis outbreaks, ranging from erythema to eczema eczema, occurred among 60 car factory workers in the UK. Workers have used cream-based chromic base paint wetted on the body of the car. In Australia, chromium is released from Newcastle Orica's explosive plant on August 8, 2011. Up to 20 workers at the plant are exposed to like 70 nearby homes in Stockton. The city was only notified three days after the release and the accident sparked a major public controversy, with Orica criticized for downplaying the level and likelihood of the leakage risk, and the state government attacked because of their slow response to the incident.
Cadmium
Cadmium Exposure is an early 20th century phenomenon, and so on. In Japan in 1910, Mitsui Mining and Smelting Company began issuing cadmium to the Jinzugawa river, as a by-product of mining operations. Residents in the surrounding area then consume rice grown in irrigation water that is contaminated with cadmium. They experience bone softening and kidney failure. The origin of these symptoms is unclear; possibilities that arise at that time include "regional or bacterial disease or lead poisoning". In 1955, cadmium was identified as a possible cause and in 1961 it was directly linked to mining operations in the area. In February 2010, cadmium was found in the exclusive jewelry of Miley Cyrus Walmart. Wal-Mart continued to sell jewelry until May, when the secret testing held by the Associated Press confirmed the original results. In June 2010, cadmium was detected on paint used in promotional drinking glasses for the Shrek Forever After movie, sold by McDonald's Restaurant, which triggered the withdrawal of 12 million cups.
Remediation
In humans, heavy metal poisoning is generally handled by the administration of chelating agents. These are chemical compounds, such as CaNa2 EDTA (calcium disodium ethylenediaminetetraacetate) which converts heavy metals into chemically inert forms that can be excreted without further interaction with the body. Chelates is not without side effects and can also remove beneficial metals from the body. Vitamin and mineral supplements are sometimes managed together for this reason.
Soils contaminated by heavy metals may be remediated by one or more of the following technologies: insulation; immobilization; reduction of toxicity; physical separation; or extraction. Isolation involves the use of hats, underground membranes or obstacles in an attempt to quarantine contaminated soil. Immobilization aims to change the soil properties so as to inhibit the mobility of heavy contaminants. Toxicity reduction tries to oxidize or reduce toxic heavy metal ions, by chemical or biological means into less toxic or moving forms. Physical separation involves removal of contaminated soil and separation of metal contaminants by mechanical means. Extraction is an on or off-site process that uses chemicals, high temperature volatization, or electrolysis to extract contaminants from the soil. The process or process used will vary according to the contaminants and characteristics of the site.
Benefits
Some elements that are considered toxic heavy metals are very important, in small quantities, for human health. These elements include vanadium, manganese, iron, cobalt, copper, zinc, selenium, strontium and molybdenum. Deficiencies of these essential metals may increase susceptibility to heavy metal poisoning.
See also
- Bento Rodrigues disaster dam
- Heavy metal detoxification
- Kingston Fossil Plant coal fly ash slurry spill
- Light metal
- Metal poisoning
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References
Source of the article : Wikipedia
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