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Description of key information

Experimental toxicokinetic studies were not available. However, as per REACH guidance document R7.C (May 2008), information on absorption, distribution, metabolisation and excretion may be deduced from the physicochemical properties. MTSC seems to be weel absorbed by oral and dermal route, and well distributed in the organism, due to the liver toxicity observed after repeated oral exposure. An excretion of MTSC via urine is expected.

Key value for chemical safety assessment

Additional information

The following remarks on the toxicokinetics of 4 -methylthiosemicarbazide (MTSC) are based on the available studies. Experimental toxicokinetic studies were not available. However, as per REACH guidance document R7.C (May 2008), information on absorption, distribution, metabolisation and excretion may be deduced from the physicochemical properties, including:

-Molecular weight: 105.16 g/mol

-Water solubility: 40.2 g/L (20°C), MTSC is highly soluble in water.

-Partition coefficient Log Kow: -1.21

-Vapour pressure: 0.0000069 Pa (25°C)

 

ABSORPTION

The physicochemical characteristics of MTSC (high water solubility) and the molecular mass (105.16 g/mol) are in the range suggestive of absorption after oral and dermal exposure. The assumption of an oral absorption is confirmed by the data acute oral toxicity with a very low LD50 in rats (15 mg/kg bw in rat). MTSC is toxic by oral route. Dermal absorption of MTSC is also confirmed by the data acute dermal toxicity (LD50 between 200 and 1000 mg/kg bw in rat).

According to the value of the low vapour pressure, MTSC is not expected to be a volatile substance.

 

DISTRIBUTION and METABOLISM

As a small molecule a wide distribution of MTSC is expected. This assumption is confirmed by the changes shown in the repeated dose toxicity studies following oral application: effects on thymus and spleen at 10 mg/kg bw/d in rats after 28-day exposure were specific to the oral administration of MTSC in rats.

No specific information was found on metabolism of MTSC.

 

EXCRETION

MTSC is probably excreted in the urine, because it is a water-soluble substance with a low molecular weight (below 300); and generally, they are conjugated metabolites from Phase II biotransformation.