Tin is a naturally-occurring metal that is soft and malleable and relatively inert in its reactions with the human body.  For this reason it has been used historically as a coating for other metals that come into contact with food, such as in tin-lined steel cans.  Unfortunately, cases of tin poisoning have occurred when acidic foods come into contact with tin coatings, and leach tin into the food.  Nowadays that tin coating is further separated from food by other coatings such as lacquers or (ultimately harmful) plastics like BPA.

Tin was first used by humans as an accidental impurity in copper ore, with the happy accident that tin turned out to be a better additive than arsenic in smelting bronze alloys.

Pure tin does not occur in the environment; it is only found in combination with other elements, such as in the mineral Cassiterite (SnO2).  Cassiterite has been sighted in Maine at various quarries from Auburn to Rumford. Today, it is mostly mined in Bolivia and a belt from China to Malaysia.

While tin is generally non-toxic in the environment owing to its insolubility in water, tin compounds called "organotins" have been developed that are quite toxic to humans and animals, and are used as biocides. These organotins are used in anti-fouling paint, in pesticides, in plastics and other materials.

 

Health Limits:

Maine Maximum Exposure Guideline limit: none established
USA Primary Drinking Water Standard limit: none established

Resources:

US Toxic Substances Portal: Tin (website)
Tin ToxFAQs Summary Sheet: Tin TOXFAQs (webpage)
Wikipedia: “Tin” (website)
Mining Data (mindat.org): “Tin

MEL Test Methods for Tin

Wastewater – EPA 200.7  (NPDES Compliant)
Non-Potable Water & Solids – EPA 6010B, 6010C (SW846) (RCRA Compliant)

Sample Requirements

Wastewater:

Container: plastic, glass
Volume: 250mL
Hold Time: 6 months if preserved with HNO3 to pH<2, otherwise 2 weeks
Preservation: HNO3 to pH<2

Solids:

Container: plastic, glass, baggie
Volume: a least 150g
Hold Time: 6 months
Preservation: n/a

Beautiful tin-bearing Cassiterite. / Kazakh Wikipedia