Everyone is concerned about environmental pollution (well, almost everyone) and how it effects the environment and human health. But did you know that some pollutants, although very toxic and dangerous, are also essential to human health?
Or put another way, did you know that some of those health food supplements you may be taking could make you very sick or even kill you?
Here is a list of 10 toxic metals – well, 9 metals and 1 metalloid, an element that exhibits some properties of metals and some of non-metals – that all show this dual nature. Some of them can cause minor health problems while others can lead to serious illness and even death, depending upon their dosage, exposure time, and how they are combined with other elements.
All images are from the following website and licensed under a Creative Commons Attribution 3.0 Unported License: Hi-Res Images of Chemical Elements, A Virtual Museum
Health effects information, unless otherwise noted, are from: Determination of Toxic Metals and Metalloids in Ambient Air
Manganese is an essential element in trace amounts but inhalation of its compounds can cause serious short-term and long-term illness. Exposures of 1-3 years have been shown to cause central nervous system disorders resulting in cramps,tremors, and hallucinations. It can also cause manganic pneumonia and renal degeneration, resulting in disability or death.. Some manganese compounds can also act as catalysts in the oxidation of some air pollutants, producing even more undesirable materials.
This picture shows a piece of limestone with black dendrites made of manganese oxide and red, iron oxide particles.
Cobalt is an essential element – it’s contained in vitamin B-12. Some cobalt compounds are also used to treat anemia and it has been used as an anti-foaming agent in beer.
Not considered as toxic as other metals, it and its compounds can cause myocardial damage, polycythemia, and affect the growth of erythrocytes.
Copper is an essential element in trace amounts and is found in a number of enzymes including phenol and cytochrome oxidases. However, it can exhibit toxicity in the form of metal fume fever, respiratory disease, and other systemic disturbances, Hemolysis of animal blood cells has also been reported.
Iron is an essential element needed for the production of hemoglobin. In larger amounts, it can inhibit certain enzymes and has been shown to cause chronic bronchitis, conjunctivitis, ritinitis, and metal fume fever. Iron oxides have been implicated as vehicles to transport high concentrations of carcinogens and sulfur compounds deep into the lungs, thereby enhancing the harmful effects of those materials.
Molybdenum is an important trace element required by the flavia-dependent metalloenzymes. It is retained in the bone and soft tissues.
Animal studies have shown that it can have serious toxic effects, including molybdenosis, loss of hair color, and adverse bone effects.
In humans it has reportedly caused liver dysfunction with hyperbilirubinemia in workmen chronically exposed in a Soviet Mo-Cu plant. In addition, signs of gout have been found in factory workers and among inhabitants of Mo-rich areas of Armenia.
Nickel is an essential element needed for enzyme activity, hormonal action, structural stability of biological macromolecules, and general metabolism.
In larger amounts, however, nickel and its compounds can cause lung cancer, dermatitis, sinus disturbances, and other respiratory diseases. Nickel carbonyl is particularly toxic.
Selenium is an essential metalloid that complexes with proteins and is distributed to all tissues of the body.
However, it can replace sulfur in cystine and methionine and block some enzyme systems. It has been connected with an increase in dental caries in children and irritates the eyes, nose, throat, and respiratory tract. Prolonged exposure may lead to gastrointestinal disorders and nervous system disturbances. It has been shown to to cause liver cancer, pneumonia, and degeneration of the liver and kidneys.
A symptom of selenium poisoning is the presence of a garlic odor on the breath.
Tin is an essential element in trace amounts and its elemental form is not considered toxic in general. However, alkyl tin compounds are highly toxic, and upon decomposition, the inorganic salts give off toxic fumes. Organic tin compounds are lipid soluble and accumulate in the central nervous system.
Vanadium is an essential element that mobilizes iron to the liver and calcium to bones. It is toxic in higher amounts, especially as pentavalent vanadium.
Human exposure of small amounts has resulted in inhibition of cholesterol synthesis. Chronic exposure to air containing vanadium has been related to mortality rates from heart disease and cancer. Higher concentrations can also result in gastrointestinal and respiratory effects.
Chromium is essential for the normal metabolism of glucose and by itself is not thought to be toxic. However, its trivalent and hexavalent compounds are dangerous, with the hexavalent form being more toxic.
Chromium compounds are suspected carcinogens and can cause perforation of the nasal septum, congestion, hyperemia, emphysema, tracheitis, bronchitis, pharyngitis, bronchopneumonia, dermatitis, and metal fume fever.