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Description of key information

A basic toxicokinetics assessment of Tin disulfide was based on physicochemical  and toxicological 
data and literature of tin disulfide, as well as on read across data from Tin sulfide. From these data,
absorption was assessed to be very low, and the oral route is considered as most appropriate route
for testing systemic toxicity. It is known that 95-99% of inorganic tin compounds are excreted via the faeces.
Distribution, metabolism and elimination were also shortly discussed, but not elaborated much into
detail based on the limited absorption.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential
Absorption rate - oral (%):
5
Absorption rate - dermal (%):
5
Absorption rate - inhalation (%):
1

Additional information

Absorption of Tin disulfide was assessed as follows based on physicochemical/toxicological data:

-  Tin disulfide is an ochre coloured odourless powder, with low molecular weight (182.84 g/mol), low water solubility (0.67 µg/L)and small particle size (d50: 1,58 µm). Based upon the physical form and low water solubility, but mainly on the absence of toxicity in acute and repeated dose oral toxicity studies, oral absorption of Tin disulfide is assumed to be very low. Looking at the literature on absorption of inorganic tin (and salts) confirms that inorganic tin is hardly absorbed after oral ingestion, possibly as a result of low solubility. In humans and laboratory species,more than 95-99% ofan ingested dose of inorganic tin is recovered in the faeces.

-  Based on the powder characteristics (respirable and inhalable particles), tin disulfide may enter the lung alveoli, but as it is not water soluble it is not considered to stay in the alveolar mucus. Acute inhalation toxicity testing showed somelaboured respiration & respiratory rate increaseon the day of exposure, however no other relevant effects of systemic toxicity were observed. Inhalation absorption is therefore considered to be of low relevance. There is further no information from literature on inhalation absorption of inorganic tin (salts).

-  Further data on surface tension (72.8 mN/m at 25°C) and absence of skin irritation, skin sensitization and dermal toxicity indicate that dermal absorption is not considered to be relevant. There is further no information from literature on dermal absorption of inorganic tin (salts).

 

For the assessment of distribution, metabolism and excretion of tin disulfide, read across from ‘tin sulfide’ was used for the repeated dose toxicity data based on structural and physicochemical but also toxicological similarity.

-   Based upon the toxiclow water solubility, but mainly based on the absence of target organs after oral application, distribution was considered minimal. Data from literature indicate that inorganic tin may distribute to various organs, however this is not considered to be relevant if there is no absorption.

-   There is no direct indication of bioaccumulation potential. Literature describes that inorganic tinmay accumulate in the bone and to a lesser extent in the liver, lung, tongue, lymph nodes and kidney, however only at very low percentages once systemically available.Taking into account that absorption for tin (di)sulfide is negligible, accumulation is not considered relevant.   

-   From the assumptions above, excretion via the urine or other body fluids is considered to be minimal. Literature data on inorganic tin (salts) confirm that orally ingested tin is excreted mainly in the faeces(about 95-99% of ingested dose in animal studies), with some additional slow elimination of the absorbed fraction in the urine.

Additional assessment based on literature of tin salts:

For the general population, the major source of tin is the diet. By comparison, drinking water and inhaled air contribute insignificant amounts. From data on mean tin intake from food for the populations of seven countries (Australia, France, Japan, Netherlands, New Zealand, the United Kingdom, and the USA), JECFA (2001) concluded that tin intakes ranged from < 1 up to 15 mg/person per day. Certain individuals who routinely consume canned fruits, vegetables, and juices from unlacquered cans could ingest 50-60 mg of tin daily (Johnson & Greger, 1982; Sherlock & Smart, 1984; JECFA, 2001). Those who consume about four servings of food stored in open unlacquered cans, on a daily basis, might consume in the region of 200 mg of tin per day (Greger & Baier, 1981; JECFA, 2001). In humans and laboratory mammals, absorption of inorganic tin from the gastrointestinal tract is low (generally less than 5 %), in particular for practically water insoluble compounds such as tin(ll) sulfide, but is influenced by dose, anion (compound solubility), and the presence of other substances. Unabsorbed ingested tin is mostly (95-99%) excreted in the faeces within 48 h. Absorbed tin distributes mainly to the bone, but also to the lungs, liver, and kidneys. Limited evidence suggests that inorganic tin does not readily cross the blood-brain barrier. Absorbed tin is mainly excreted in the urine, with some additional biliary excretion occurring. In mice, the biological half-life of absorbed inorganic tin was approximately 30 days. There is little or no evidence that practically water insoluble tin compounds pose any significant health risk at the exposure levels found in the work environment (European Commission, 2003).