Table 3.

Key facts on potentially toxic elements

Element	Key facts	Bioavailability	Deficiency	Toxicity
F	F in the form of fluoride occurs in nature ubiquitously. F has been suggested as a therapeutic agent in the treatment of osteoporosis.	F enters the body through drinking waters and foods. Other important sources of F are tea, seafood, and toothpastes. Most of the ingested F is absorbed from the upper intestines and is taken up by bones and teeth and the rest is lost in the urine.	Low levels of F in drinking water lead to dental decay.	High levels of dietary F cause dental fluorosis and mottling of tooth enamel is a well-known feature of excess F ingested.
Pb	Pb is a toxic element that affects multiple body systems and is particularly is harmful to young children. Human exposure is usually assessed through the measurement of Pb in whole blood. There is no known level of Pb exposure that is considered safe.	After absorption, 99% of Pb is bound to the hemoglobin portion of erythrocytes and is circulated via the vascular system to soft tissues, liver kidneys, bone, brain, and hair. Pb is stored in the teeth and bones, where it accumulates over time. Pb in bone is released into blood during pregnancy that becomes a source of exposure to the developing fetus.		Appearance of a “lead line” also known as a “Burtonian blue” line, at the gum line, is indicative of chronic lead poisoning. Long-term exposure in adults causes anemia, hypertension, renal impairment, immunotoxicity, and toxicity to the reproductive organs. The neurological and behavioral effects of lead are irreversible.
Cd	Cd does not play a role in higher biologic systems or human nutrition. Dermal exposure is not a typical human health concern as Cd does not penetrate the skin barrier.	The primary source of Cd exposure for nonsmokers is from the food supply in general, leafy vegetables. Regular use of tobacco-containing products is a common route of cadmium exposure for smokers.		In occupational work places inhalation is the primary route of exposure. Ouch Ouch or Itai-Ita disease is unique to long-term consumption of Cd-contaminated rice.
Hg	Hg is a common chemical exposure and environmental pollutant. It exists in organic and inorganic forms. Elemental and methylmercury are toxic to the central and peripheral nervous systems.	Exposure mainly occurs through consumption of contaminated fish and shellfish and through worker inhalation. Excretion of Hg depends on its original form.		Mercury vapor, in the atmosphere, is typically low and not considered a major route of exposure.
Al	Aluminum sulfate is a common additive to drinking water worldwide used as a “clarifying agent.” Due to Al intake through common food itms, all people have some level of Al in their urine.	Al is poorly absorbed via ingestion and inhalation and is essentially not absorbed dermally. Excretion for absorbed Al is through urine.		Neurotoxic effects of Al in dialysis patients treated with Al-containing dialysis fluids have been demonstrated.
As	As is highly toxic and exists in inorganic and organic forms. Inorganic As is the most significant chemical contaminant in drinking-water globally.	Both inorganic and organic As forms leave the body through urine.		Inorganic As is toxic and is a confirmed carcinogen. Organic As compounds are less harmful. Long-term exposure to inorganic As, mainly through drinking water and food, can lead to chronic arsenic poisoning, skin lesions, and skin cancer.
Sn	Sn is used in food industry to line canned food and beverages and this is the major route of human exposure to it. Sn as single atoms or molecules is not very toxic to any kind of organism.	Sn and inorganic Sn compounds are poorly absorbed from the GI tract after oral (eating/drinking) or inhalation (breathing in) and dermal exposure (skin contact) and they do not accumulate in tissues. They are rapidly excreted, primarily in the feces, and therefore, they do not usually cause harmful effects.	There is no evidence that Sn is an essential element for humans.	Toxic form of Sn is the organic form (organotin) and its toxicity has been epidemiologically linked to several markers of impaired health and growth in animal models.
Li	Li is the first choice in treating bipolar disorders. Li has beneficial pharmacological properties (antimanic).	Lithium absorption is through the GI.		Individuals may stop their treatment at some point. Three organ systems that may be negatively affected by Li in long-term use are the thyroid gland, kidneys, and parathyroid gland.

F=Fluorine, Pb=Lead, Cd=Cadmium, Hg=Mercury/hydrargyrium, Al=Aluminium, As=Arsenic, Sn=Stannum/tin, Li=Lithium, GI=Gastrointestinal tract