Tin is a soft, insoluble metal extensively used in the caning industry to line food, beverage and aerosol cans. It is present in brass, bronze, pewter and solder. Tin can be combined with other elements (chlorine, sulphur, oxygen) to form so called inorganic tin, these compounds are present in toothpastes, food additives, colourants, perfumes and soaps. Organotin compounds – alkyl and phenyl derivatives – are used in the manufacture of plastic pipes, food packaging, wood preservatives, antifouling paints and rodenticides.
Normal population exposure is primarily from food and drinking water. Tin in its various forms is present in normal soils and hence vegetables. Food preserved in tin lined cans is a significant source of tin in the diet; however more than 90 % of cans are lacquered to prevent contact of food with the tin, reducing the tin content of the food from 100 ppm in unlacquered cans to 25 ppm in lacquered cans. Light coloured fruit and fruit juices are an exception being packed in unlacquered cans; the tin helps preserve the colour of the fruit. Stannous fluoride is often added to toothpaste. Seafood and drinking water may also contain tin (butyltin) as leachates from antifouling paints and PVC pipes. Occupational exposure occurs in processing industries which work with tin containing compounds, exposure is generally through inhalation of dust.
Only small amounts of inorganic tin and tin compounds are absorbed from the gastrointestinal tract and the urine is the main route for excretion. The majority of ingested tin is excreted within 24 hours but some can be retained in the bones and tissues for 2 – 3 months. Acute health effects from ingestion of large quantities of tin include abdominal pain, anaemia, hepatic and renal dysfunction. Tin absorption reduces the absorption of zinc.
Organic tin compounds (alkyl- and phenyltin derivatives) can cause a range of toxic effects after inhalation, ingestion or dermal exposure. These include skin, eye and respiratory irritation. Acute and chronic neurological problems have also been reported. Very large acute ingestions may be lethal.
Recommended sampling time is PRE SHIFT - following a period of 16 hours with no exposure OR - POST SHIFT - the last 2 hours to immediately following the end of the working day.
Aliquot to Core laboratory for UCRN
The urine pottle used for specimen collection must be shown to be free of Tin contamination. Tin is a dietary related metal, for monitoring a pre and post exposure sample is suggested.
Ambient (8 - 24 degrees Celsius)
Reports issued by Canterbury Health laboratories will have results along with current Normal population Reference Intervals (RI).
For interpretation against Biological exposure indexes (BEI) please refer to the latest Worksafe’s : Biological Exposure Index (BEI) review.
See link in “Additional Information” tab below for Workplace Exposure Standards on the Worksafe.govt.nz website
Tin/creatinine ratio 0-11 nmol/mmol
To convert urine tin nmol/L to ug/L multiply by 0.119
For example 200 nmol/L = 24 ug/L (1 ppb).
No Biological Exposure Index is available for Tin
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