4-methylpent-3-en-2-one

Endpoint summary

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

There is no toxicokinetics, metabolism and distribution data available on mesityl oxide (4-methylpent-3-en-2-one). Therefore, the assessment of the toxicokinetics of 4-methylpent-3-en-2-one is based on the available toxicological data and the physicochemical properties as suggested by the REACH Guidance Chapter R.7c:

Molecular weight: 98.14 g/mole

Water solubility: 27 g/L at 20°C

Partition coefficient log Kow = 1.37

 

ABSORPTION

 

Oral route

 

According to the REACH Guidance, the physicochemical characteristics of 4-methylpent-3-en-2-one (log Kow 1.37) and the molecular mass (98.14 g/mol) are in a range suggestive of absorption as such from the gastro-intestinal tract subsequent to oral ingestion. This assumption of oral absorption is confirmed by the mortality observed at 2000 mg/kg bw in the acute oral toxicity study (Corvaro, 2010). Therefore, the oral absorption of4-methylpent-3-en-2-onecan be assumed to be 100% for risk assessment.

 

Inhalation route

 

According to the REACH Guidance, the physicochemical characteristics of 4-methylpent-3-en-2-one (log Kow 1.37) and the molecular mass (98.14 g/mol) are in a range suggestive of absorption as such from the respiratory subsequent to inhalation exposure. This assumption of absorption is confirmed by the LC50 of 4.53 mg/L in the acute inhalation toxicity study (Hine et al., 1960), which is equivalent to an internal dose of 860 mg/kg, assuming an inhalation absorption of 100%.

 

Dermal absorption

 

According to the REACH Guidance, the n-Octanol/water partition coefficient ((log Kow), the water solubility and molecular weight of 4-methylpent-3-en-2-oneare in ranges which favour dermal absorption. However, the acute dermal LD50 of 5150 mg/kg (Topping et al., 1994) compared to the LC 100 of 2000 mg/kg in the acute oral toxicity study (Corvaro, 2010) indicates a lower dermal absorption compared to the oral route. In such circumstances a dermal absorption of 10% is usually used, however by precaution, a dermal absorption of 50% will be used for risk assessment.

 

DISTRIBUTION and METABOLISM

 

According to the REACH Guidance, as a small molecule a wide distribution of 4-methylpent-3-en-2-one is expected. 

Patty's Toxicology states that "information on the metabolism of 4-methylpent-3-en-2-one is fragmentary. It has been reported that metabolism occurs through formation of a glucuronide".

ELIMINATION

 

According to the REACH Guidance, the n-Octanol/water partition coefficient (log Pow of 1.37) is not suggestive of accumulation of unchanged 4-methylpent-3-en-2-one in fatty tissues subsequent to absorption. While absorbed 4-methylpent-3-en-2-one

is reduced in the body to an appreciable extent, repeated exposure of animals to non-lethal concentrations suggests that 4-methylpent-3-en-2-one is probably not rapidly eliminated. After frequent exposures, blood concentrations can reach anesthetic levels (HSDB, 2005).