Zinc toxicity
Encyclopedia
Even though zinc
is an essential requirement for a healthy body, excess zinc can be harmful, and cause zinc toxicity. Excessive absorption of zinc can suppress copper and iron absorption. The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish. The Free Ion Activity Model (FIAM) is well-established in the literature, and shows that just micromolar
amounts of the free ion kills some organisms. A recent example showed 6 micromolar killing 93% of all Daphnia
in water.
The free zinc ion is also a powerful Lewis acid
up to the point of being corrosive
. Stomach acid contains hydrochloric acid
, in which metallic zinc dissolves readily to give corrosive zinc chloride
. Swallowing a post-1982 American one cent
piece (97.5% zinc) can cause damage to the stomach lining due to the high solubility of the zinc ion in the acidic stomach.
There is evidence of induced copper deficiency
at low intakes of 100–300 mg Zn/d. The USDA RDA is 15 mg Zn/d. Even lower levels, closer to the RDA, may interfere with the utilization of copper and iron or to adversely affect cholesterol.
There is also a condition called the zinc shakes or "zinc chills" that can be induced by the inhalation of freshly formed zinc oxide
formed during the welding
of galvanized materials.
began minting pennies
coated in copper but made primarily of zinc. With the new zinc pennies, there is the potential for zinc toxicosis, which can be fatal. One reported case of chronic ingestion of 425 pennies (over 1 kg of zinc) resulted in death due to gastrointestinal bacterial and fungal sepsis, while another patient, who ingested 12 grams of zinc, only showed lethargy and ataxia
(gross lack of coordination of muscle movements). Several other cases are reported of humans suffering zinc intoxication by the ingestion of zinc coins.
Pennies and other small coins are sometimes ingested by dogs, resulting in the need for medical treatment to remove the foreign body. The zinc content of some coins can also cause zinc toxicity, which is commonly fatal in dogs, where it causes a severe hemolytic anemia
, also liver or kidney damage; vomiting and diarrhoea are possible symptoms. Zinc is highly toxic in parrots and poisoning can often be fatal.
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
is an essential requirement for a healthy body, excess zinc can be harmful, and cause zinc toxicity. Excessive absorption of zinc can suppress copper and iron absorption. The free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish. The Free Ion Activity Model (FIAM) is well-established in the literature, and shows that just micromolar
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
amounts of the free ion kills some organisms. A recent example showed 6 micromolar killing 93% of all Daphnia
Daphnia
Daphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style...
in water.
The free zinc ion is also a powerful Lewis acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
up to the point of being corrosive
Corrosive
A corrosive substance is one that will destroy or irreversibly damage another surface or substance with which it comes into contact. The main hazards to people include damage to the eyes, the skin, and the tissue under the skin; inhalation or ingestion of a corrosive substance can damage the...
. Stomach acid contains hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
, in which metallic zinc dissolves readily to give corrosive zinc chloride
Zinc chloride
Zinc chloride is the name of chemical compound with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. ZnCl2 itself is hygroscopic and even deliquescent. Samples should therefore be protected from...
. Swallowing a post-1982 American one cent
Cent (United States coin)
The United States one-cent coin, commonly known as a penny, is a unit of currency equaling one one-hundredth of a United States dollar. The cent's symbol is ¢. Its obverse has featured the profile of President Abraham Lincoln since 1909, the centennial of his birth. From 1959 to 2008, the reverse...
piece (97.5% zinc) can cause damage to the stomach lining due to the high solubility of the zinc ion in the acidic stomach.
There is evidence of induced copper deficiency
Copper deficiency
Copper deficiency is a very rare hematological and neurological disorder. The neurodegenerative syndrome of copper deficiency has been recognized for some time in ruminant animals, in which it is commonly known as "swayback" The disease involves a nutritional deficiency in the trace element copper...
at low intakes of 100–300 mg Zn/d. The USDA RDA is 15 mg Zn/d. Even lower levels, closer to the RDA, may interfere with the utilization of copper and iron or to adversely affect cholesterol.
There is also a condition called the zinc shakes or "zinc chills" that can be induced by the inhalation of freshly formed zinc oxide
Zinc oxide
Zinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...
formed during the welding
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
of galvanized materials.
Poisoning
In 1983, the United States MintUnited States Mint
The United States Mint primarily produces circulating coinage for the United States to conduct its trade and commerce. The Mint was created by Congress with the Coinage Act of 1792, and placed within the Department of State...
began minting pennies
Cent (United States coin)
The United States one-cent coin, commonly known as a penny, is a unit of currency equaling one one-hundredth of a United States dollar. The cent's symbol is ¢. Its obverse has featured the profile of President Abraham Lincoln since 1909, the centennial of his birth. From 1959 to 2008, the reverse...
coated in copper but made primarily of zinc. With the new zinc pennies, there is the potential for zinc toxicosis, which can be fatal. One reported case of chronic ingestion of 425 pennies (over 1 kg of zinc) resulted in death due to gastrointestinal bacterial and fungal sepsis, while another patient, who ingested 12 grams of zinc, only showed lethargy and ataxia
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
(gross lack of coordination of muscle movements). Several other cases are reported of humans suffering zinc intoxication by the ingestion of zinc coins.
Pennies and other small coins are sometimes ingested by dogs, resulting in the need for medical treatment to remove the foreign body. The zinc content of some coins can also cause zinc toxicity, which is commonly fatal in dogs, where it causes a severe hemolytic anemia
Hemolytic anemia
Hemolytic anemia is a form of anemia due to hemolysis, the abnormal breakdown of red blood cells , either in the blood vessels or elsewhere in the human body . It has numerous possible causes, ranging from relatively harmless to life-threatening...
, also liver or kidney damage; vomiting and diarrhoea are possible symptoms. Zinc is highly toxic in parrots and poisoning can often be fatal.