TIN (Sn)

ATOMIC NUMBER: 50

GROUP 14: CARBON, SILICON, GERMANIUM, AND LEAD

The use of tin has been dated as far back as 3,000 B.C., culminating in some 5,000 years of interaction with human society. Trademark to its best-known properties, when a bar of tin is bent, the silvery-white crystalline metal makes a crackling sound known as the “tin cry.”

Dating back to the 1880s, workers exposed to tin vapors complained of symptoms such as headaches, nausea, and general fatigue. A medical treatment for skin infections using triethyltin was known to poison more than 200 patients in the 1950s in France, ultimately killing more than one hundred of them via cardiac arrest, coma, or serious complications from convulsions, while those affected but not killed frequently suffered years of ongoing headaches and visual complications.²⁷⁶ However, health risks from tin exposure are not nearly as acute as risks from more toxic metals such as lead and mercury.

While tin is familiar in its many industrial uses, its organic form, organotin, poses the most risk to humans due to its toxic effects. These forms include trimethyltin and triethyltin, both of which exhibit neurotoxicological effects.²⁷⁷

Initial studies on tin found relatively low toxicity in its inorganic compounds, which were poorly absorbed, limiting accumulation to low levels.278 The same data show that organic tin compounds synthetically produced starting in the 1960s posed potential problems for the growth, survival, and continuity of animal species, while observed disruptions in exposed animals’ behavior suggest neurological development issues. Animal studies involving tin(II) fluoride and tin(II) chloride have been shown to reduce or inhibit the natural functions of the liver.^279,280,281 Tin(II) tartrate was also found to cause a decrease in the antioxidant glutathione, ultimately leading to liver damage in animal studies.²⁸²

The public’s biggest exposure to tin comes from foods containing trimethyltin and triethyltin organic compounds, with a focus on seafoods and canned foods. Like other metals, tin has been found to accumulate in shellfish and other seafood. According to the Food Safety Authority of Ireland (FSAI), fish is the number one tin-accumulating culprit, food-wise.²⁸³ In environmental impact studies, trialkyltins have been found to be the most toxic on algae species.²⁸⁴

Because tin is relatively noncorrosive, it is almost ubiquitously used in food cans. Tin may leach into the food stored inside those cans, though the amount varies widely based on a multitude of factors including the type of food, pH of the food, food additives present, and so on. Canned foods—some 90 percent of which use tin compounds—with high pH levels have been found to contain between 100 and 500 ppm of tin.²⁸⁵

Although trace amounts of tin can be found naturally in water, inorganic tin-based pesticides and industrial waste are substantially increasing the tin contamination of waterways.²⁸⁶

Agri Tin^®, registered trademark of the Nufarm brand, is a fungicide/pesticide composed of triphenyltin hydroxide and used on potatoes, sugar beets, pecans, and other crops. Its product label warns that, like other toxic substances, it must be handled by a certified applicator due to the danger of “affecting fetal development” and its general carcinogenicity at high doses.²⁸⁷

These issues may be amplified by the fact that tin has a strong affinity for soils, persisting in soils for long periods of time while presenting the possibility of bioabsorption and accumulation through human consumption.²⁸⁸

“Swallowing large amounts of inorganic tin compounds may cause stomachache, anemia, and liver and kidney problems,” says the Tin Compounds fact sheet for the Agency for Toxic Substances and Disease Registry. “Humans exposed for a short period of time to some organic tin compounds have experienced skin and eye irritation and neurological problems; exposure to very high amounts may be lethal.”289

Tin is commonly referred to in industrial uses by the term stannous, reflecting the Latin base for tin, stannum, and its abbreviation on the periodic table, Sn.

Stannous fluoride—composed of tin(II) and fluoride—is one of the most common types of fluoride applied in dentistry to prevent cavities (administered orally) and put in many toothpastes to prevent tooth decay, often under the trade name “Fluoristan,” a generally more expensive variation of fluoride that has been used in formulas for name brands such as Crest and Oral B. The fluoride salt is also added to some municipal water supplies, though the sodium fluoride and fluorosilicic acid species are more common. Stannous fluoride carries the risks of other fluoride compounds, including osteosarcoma, osteoporosis, and fluorosis.²⁹⁰

Fluoristan (containing tin and fluoride) has caused death in at least a few acute cases of poisoning. In January 1979, the parents of a three-year-old boy in New York were awarded $750,000 after the child ingested a lethal dose of stannous fluoride gel that was spread on his teeth to prevent decay.²⁹¹ The hygienist had reportedly failed to give proper instruction to spit out the solution, instead neglecting to prevent the young child from swallowing some 45 cubic centimeters of 2 percent stannous fluoride solution, estimated by the Nassau County toxicologist to be three times a deadly amount for the boy’s size and weight.

Studies involving humans have confirmed that tin competes with zinc, so too much dietary tin can decrease the amount of zinc a person can absorb.

One way to remove heavy levels of tin in the body is through the chelation properties of quercetin, a flavonoid found in many fruits and vegetables, according to a study that revealed it was effective for removing stannous versions of tin.²⁹²

Overall, though tin poses some dangerous neurotoxic and carcinogenic effects, its potential for cancer and disease via chronic, low-level exposure throughout the food chain is typically lower than many other common heavy metals. It is not as absorbable and often less accumulated than more problematic peers such as mercury, lead, cadmium, and arsenic.

At the Natural News Forensic Food Lab, we don’t currently test for tin. It requires a unique methodology, so it’s not something we currently track in foods.