Tin (Sn)

Tin was one of the earliest metals used by humans as a structural material and also as a chemical that had a large variety of purposes. Cassiterite is the primary tin-bearing ore which contains about 78-79% elemental tin. It is found scattered in large amounts in varying geographical areas.

Tin is often found in peat, clays, and a wide variety of soils and fertilizers. Tin is more commonly found in soil than other trace nutrients such as zinc or molybdenum. Furthermore, it is found in all kinds of plant life from pasture grasses, trees, moss, garden vegetables and wheat.

Organic and inorganic tin have been found in fish, sea shells, coral and algae over 100 years ago.  Relatively high amounts of tin are found in the air, and there appears to be more tin found in the air then in the Earth’s crust or oceans. The large source of tin in the atmosphere is from burning coal and oil. It is also found in chicken eggs as well as other animal products such as cow’s milk, beef, mutton, seafood and other meat products. Tin has also been found in various culinary oils such as vegetable and peanut oil. It seems like tin can accumulate in all mammalian tissues (Cardarelli, 2019).

The presence of tin on a hair tissue mineral analysis is generally perceived as an environmental contamination, however it has been observed in the laboratory to accelerate growth in rats by nearly 60% and meets the requirements for an essential trace element for them (Schwarz K, 1970). Rats fed a diet deficient in tin resulted in poor growth, lowered response to sound, and alopecia, with decreased food efficiency (Yokoi K, 1990).

Although tin has not been found to be essential for humans (Nielsen FH, 1974), symptoms of tin deficiency may be similar to that found in rats and may contribute to hearing loss.

Dr Joel Wallach has put forth the idea that tin and tinnitus have a correlation, which has not yet been substantiated. However tin has been shown to have some anti-cancer properties in humans (Rocamora-Reverte L, 2012).

Tin is often perceived as a toxic element, however if tin were found to be a vital trace nutrient, one of the criteria would be for it to be universally available to the living organisms which require it. Its presence is not enough for one to infer that tin is an essential nutrient. Tin must also accumulate in the food chain and be used by these organisms in one way or another (Cardarelli, 2019).

Tin is widely distributed in the human body; however, it showed less frequency of detection in the brain and muscle tissue. In newborns, tissue tin is undetectable, with the exception of the lungs, which may have come from inhalation and rapidly increases with age. It seems as though only a very limited amount of tin crosses the placenta (ATSDR (Agency for Toxic Substances and Disease Registry) Toxicological Profile for Tin and Compounds, 2005). 

Sources

The interest in tin was initially focused at its potential for toxicity in humans due to its contact in foods such as tin-coated cans, tinfoil and organotin pesticides.

Tin cans, interestingly contained more lead than tin.  Most fresh and frozen foods usually contain less than 1mcg of tin per gram. Canned foods is still a major source of tin. Dietary intake of tin is approximately 1-2.3 mg per kg of food eaten. Acids such as acetic, tartaric and citric that are commonly found in various foods can dissolve metallic tin and contaminate food (Namik K Aras, 2007). A common source for elevated tin levels is from swimming in water that is located near cities (Cardarelli, 2019).. 

Toxicity

Tin is found in both inorganic and organic forms. The words “stannous” and “stannic” refer to tin salts with a valence of +2 and +4. Stannous fluoride is used in toothpaste. The inorganic forms are not toxic unless consumed in high doses, while the organic forms are quite toxic. Inorganic tin can be released into food from tin coated copper cooking utensils.  

Tin poisoning as a result of food and consumption has been reported. Fruit punch containing 2,000 ppm of tin (Warburton S, 1962), apple juice at 250-385 ppm and tomato juice between 141-405 ppm (Barker WH, 1972) have been observed to produce acute gastric disturbances. Canned foods such as salmon, fruit salad and rhubarb in which the levels of tin range from 250-650 ppm have also been reported to have toxic effects (Benoy CJ, 1971). Symptoms of tin toxicity typically include nausea, abdominal cramps and perhaps vomiting within 1-2 hours of ingestion and last around 48 hours.

In contrast to the above on Tin poisoning, no adverse effects have been found in health y adults consuming tin at levels up to 267 mg/kg in canned food (Boogard, et al., 2003). Five human volunteers showed no toxic effects after consuming tin at doses of 1.59-3.58 mg/kg body weight in orange juice (Benoy CJ, 1971). When human volunteers were administered fruit juice containing 1.4 g/L tin in amounts corresponding to 5-7 mg/kg of body weight, mild signs of toxicity in the form of gastric irritation were reported. The nausea and other symptoms that were observed, were likely due to irritation of the mucous membranes of the alimentary canal and not from the absorption of tin (Benoy CJ, 1971). Another study using human volunteers given canned juice (pH 3.9) containing 500 mg/L of tin (1.59-2.65 mg/kg of bodyweight) failed to show symptoms of acute toxicity (Dack, 1955).

Signs and symptoms of organic tin toxicity include:

• Headache

• Muscle ataxia

• Fatigue

• Vertigo

• Reduced sense of smell

• Kidney damage

• Skin, eye and digestive tract irritation

• Inflammation of the biliary tract.

• Testicular degeneration.

• Forgetfulness

• Lack of motivation

• Headaches

• Loss of libido and

• Sleep disturbances.

• Brain swelling and brain damage can result in a large number of symptoms including clumsiness, disorientation, seizures, nystagmus, loss of vision and hearing, vertigo, loss of sensation, phantom pain in the hands and feet, and other nerve problems

• Other conditions include hyperglycemia, lesions in testes and ovaries, and inflammation or congestion of binary ducts. Erythrocyte hemolysis, anemia and subnormal lymphocytes may occur, causing immune dysfunction.

• Psychological effects of organic tin toxicity include mood disorders which can have bouts of rage and deep depression which can last for hours and even days. 

Signs and symptoms of chronic toxicity from inorganic tin include:

• Nausea

• Vomiting

• Abdominal pain

• Diarrhoea

• Weakness

• Easy fatigability

• Malaise

• Generalised pain

• Depression

• Profuse sweating

• Anaemia

• Reduced lifespan

• Increased birth weight

• Increased infant mortality and miscarriages.

Psychological effects of organic tin toxicity include mood disorders which can have bouts of rage and deep depression which can last for hours and even days.

Hair Tissue Mineral Analysis

The tin levels in hair are thought to reflect environmental exposure when an individual’s mineral transport is normal. In people with deranged mineral transport, hair tin levels can be dramatically elevated due to mercury induced retention. There is no use of trying to lower tin levels directly. When the mineral levels and ratios are improved, tin levels come down into normal levels on their own.

The significance of low levels of tin on a hair test is uncertain at this time. However, elevated levels of tin can interfere with iron metabolism and produces heme breakdown. Tin also increases the excretion of selenium and zinc; thus, these elements may be artificially raised on a hair test when tin is elevated (Watts, 2010).

Adequate copper and iron intake appear to be mildly protective against tin toxicity (Cutler, 2004).

References

1. ATSDR (Agency for Toxic Substances and Disease Registry) Toxicological Profile for Tin and Compounds. (2005). Toxicological Profile for Tin and Compounds. Atlanta: US Department of Health and Human Services, Public Health Service; Agency for Toxic Substances and Disease Registry.

2. Barker WH, R. V. (1972). Tomato juice-associated gastroenteritis, Washington and Oregon, 1969. American Journal of Epidemiology, 96(3), 219-26. doi:10.1093/oxfordjournals.aje.a121451

3. Benoy CJ, H. P. (1971). The toxicity of tin in canned fruit juices and solid foods. Food and cosmoetics toxicology, 645-56.

4. Boogard, P. J., Boisset, M., Blunden, S., Davies, S., Ong, T. J., & Taverne, J.-P. (2003). Comparative assessment of gastrointestinal irritant potency in man of tin(II) chloride and tin migrated from packaging. Food and Chemical Toxicology, 41(12), 1663-1670. doi:10.1016/S0278-6915(03)00216-3

5. Cardarelli, N. F. (2019). Tin as a Vital Nutrient: Implications in Cancer Prophylaxis and other Physiological Processes. CRC.

6. Cutler, A. H. (2004). Hair Test Interpretation: Finding Hidden Toxicities.

7. Dack, G. (1955). Chemical poisons in food. In U. N. Programme., & W. H. Organization., Tin and organotin compounds : a preliminary review. (pp. 24-25). Geneva : World Health Organization, 1980.

8. INCHEM. (n.d.). Tin (WHO Food Additives Series 24). Retrieved from IPCS INCHEM: http://www.inchem.org/documents/jecfa/jecmono/v024je13.htm

9. INCHEM. (n.d.). Tin and Stannous Chloride (WHO Food Additive Series 17). Retrieved from IPCS INCHEM: http://www.inchem.org/documents/jecfa/jecmono/v17je32.htm

10. Namik K Aras, O. Y. (2007). Essentiality and Toxicity of Some Trace Elements and Their Determination. In O. Y. Namik K Aras, Trace Element Analysis of Food and Diet (p. 362). Royal Society of Chemistry.

11. Nielsen FH, S. H. (1974, May). Are nickel, vanadium, silicon, fluorine, and tin essential for man? A review. American Journal of Clinical Nutrition, 27(5), 515-20. doi:10.1093/ajcn/27.5.515

12. Rocamora-Reverte L, C.-G. E.-T.-R. (2012). Study of the anticancer properties of tin(IV) carboxylate complexes on a panel of human tumor cell lines. ChemMedChem., 7(2), 301-310. doi:10.1002/cmdc.201100432

13. Schwarz K, M. D. (1970, July). Growth effects of tin compounds in rats maintained in a trace element-controlled environment. Biochemical and biophysical Research and Communications, 13(40), 22-9. doi:10.1016/0006-291x(70)91040-5

14. Warburton S, U. W. (1962). Outbreak of foodborne illness attributed to tin. Public Health Reports, 77, 798-800. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/14004911

15. Watts, D. L. (2010). Trace Elements and Other Essentia nutrients. Writer's Block.

16. Yokoi K, K. M. (1990). Effect of dietary tin deficiency on growth and mineral status in rats. Biological Trace Element Research, 223-31. doi:10.1007/bf02917210