Methyl acetoacetate

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

29.167 mg/m³

Most sensitive endpoint:

repeated dose toxicity

Route of original study:

Oral

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

30

Modified dose descriptor starting point:

NOAEC

Value:

875 mg/m³

Explanation for the modification of the dose descriptor starting point:

Oral absorption is estimated to be approximately 50%; inhalation absorption of 100% is assumed

AF for dose response relationship:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance. The use of a larger AF is not warranted on the basis of the data available

AF for differences in duration of exposure:

6

Justification:

Starting point was extrapolated from a subacute to a chronic exposure period

AF for interspecies differences (allometric scaling):

4

Justification:

A default AF of 4 is used, according to ECHA REACH Guidance

AF for other interspecies differences:

1

Justification:

AF 1 used, no indication for differences in toxicokinetics and toxicodynamics

AF for intraspecies differences:

5

Justification:

A default AF of 5 is used, according to ECHA REACH Guidance

AF for the quality of the whole database:

1

Justification:

AF of 1 is appropriate: the database is comprehensive and of good quality

AF for remaining uncertainties:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Route of original study:

Oral

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

8.33 mg/kg bw/day

Most sensitive endpoint:

repeated dose toxicity

Route of original study:

Oral

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

120

Modified dose descriptor starting point:

NOAEL

Value:

1 000 mg/kg bw/day

Explanation for the modification of the dose descriptor starting point:

Data indicate a similar extent of absorption following oral and dermal exposure; correction for differences in the extent of absorption is not required.

AF for dose response relationship:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance. The use of a larger AF is not warranted on the basis of the data available.

AF for differences in duration of exposure:

6

Justification:

Starting point was extrapolated from a subacute to a chronic exposure period

AF for interspecies differences (allometric scaling):

4

Justification:

A default AF of 4 is used, according to ECHA REACH Guidance.

AF for other interspecies differences:

1

Justification:

AF 1 used, no indication for differences in toxicokinetics and toxicodynamics

AF for intraspecies differences:

5

Justification:

A default AF of 5 is used, according to ECHA REACH Guidance.

AF for the quality of the whole database:

1

Justification:

AF of 1 is appropriate: the database is comprehensive and of good quality.

AF for remaining uncertainties:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance.

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:

high hazard (no threshold derived)

Additional information - workers

Toxicology summary

Toxicokinetics

MAA is a small, mobile, relatively volatile and uncharged molecule with excellent solubility in hydrophilic and hydrophobic solvents. It is rapidly and almost completely absorbed after oral exposure. Absorption via the dermis is comparatively lower which may also be due to the volatile behavior. MAA is rapidly excreted after hydrolysis of the ester function and also rapidly eliminated during metabolism. Tests with repeated dose administration demonstrate that outside lethal doses the effects of MAA are completely reversible. Cumulation in the body can be excluded.

Acute toxicity

Acute oral toxicity

The acute oral toxicity on rats was determined to be 2580 mg/kg.

Acute dermal toxicity

The acute dermal toxicity on rats was found to be > 2000 mg/kg.

Acute inhalation toxicity

Study not performed; dermal route was chosen instead.

Irritation/Corrosion

MAA was found to be non-irritating to skin and severely irritating to eyes, therefore the substance should be classified as severe eye-irritant - Category 1 (irreversible effect on the eye) according to Regulation (EC) No. 1272/2008.

Sensitisation

MAA is not a skin sensitiser.

Repeated dose toxicity

The appropriate dose levels were evaluated in a 7 -day-range-finding test. Based on this RF-study, dose levels of 0, 100, 300 and 1000 mg/kg b.w./day were fixed for the main study, including 2-weeks recovery for low and high dose groups. There were neither premature deaths nor clinical signs as a result of treatment with MAA. There were some minor effects observed on body weights, hematology, clinical chemistry, urinalysis, and organ weights. However, all these findings were either incidental or within the normal background range and therefore not considered to be of toxicological significance and treatment-related. There were also no necropsy and histological findings. In conclusion, in the absence of any effect, the NOEL and NOAEL were determined to be 1000 mg/kg/day.

Genetic toxicity

The test item MAA was tested for genetic toxicity in several in-vitro studies in 1988 and 1995, both with and without metabolic activation. A reverse mutation assay (Ames test) as well as a chromosomal aberration test were performed according to the corresponding OECD-guidelines. The Ames test used Salmonella typhimurium and E.coli strains and showed a negative result (non-mutagenic). An additional Ames test published in literature (JETOC no.43) showed a negative result as well and confirmed the non-mutagenic result of the first study.

The chromosomal aberration test performed with Chinese hamster ovary cells showed clastogenic effects. However, this clastogenic response at higher concentrations in presence of S9 -mix might be rather a secondary effect due to possible degradation products than a substance specific property. This assumption is confirmed by the additional experiment with pH-adjustment, where no clastogenic effects were observed up to 2500 microgr/ml. In another chromosomal aberration test performed in Japan and published in literature; this study was performed with pH-adjustment and showed a non-clastogenic result- confirming the assumption explained above.

Toxicity to reproduction

The study was performed according to OECD-guideline no. 422. MAA at dosages of 0 (vehicle control), 100, 300 and 1000 mg/kg/day was orally administered to Crj:CD(SD) male and female rats (12 animals/sex/group) from 14 days before mating through the mating period and up to the day before necropsy (Total: 35 days) in males and 14 days prior to mating through the gestation period up to day 3 of delivery in females to investigate the effect on the repeat dose and reproductive toxicity for the parent animals and the development for the offspring, and the following results were obtained.

Repeat dose toxicity:

There were some effects observed on the clinical signs, blood chemistry and some histopathological parameters. These changes were seen in single animals only, without dose dependency. Therefore, these findings were considered to be of incidental nature and not related to treatment with the test article. No effects were reported on the remaining parameters such as body weight, food consumption, hematology

Reproductive/developmental toxicity:

As for reproductive performance in parent animal, no effects of administration of test article were observed on the estrus cycle, numbers of corpora lutea or implantations, copulation (mating performance) or fertility indices. Examination at delivery and during the lactation period revealed, no effects of administration of test article were observed on the gestational days, number of litter or live newborns, gestation, birth or stillbirth indices, sex ratio, body weight at birth or on day 4 after birth, viability index on day 4 after birth. No external malformations in live newborns were observed. As described above, the no observed effect level (NOEL) under this study conditions was assumed to be 1000 mg/kg/day for repeat dose toxicity in both males and females, and also to be 1000 mg/kg/day for reproductive/developmental toxicity in parent animals and offspring.

General Population - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

6.25 mg/m³

Most sensitive endpoint:

repeated dose toxicity

Route of original study:

Oral

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

60

Modified dose descriptor starting point:

NOAEC

Value:

375 mg/m³

Explanation for the modification of the dose descriptor starting point:

Oral absorption is estimated to be approximately 50%; inhalation absorption of 100% is assumed

AF for dose response relationship:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance. The use of a larger AF is not warranted on the basis of the data available

AF for differences in duration of exposure:

6

Justification:

Starting point was extrapolated from a subacute to a chronic exposure period

AF for interspecies differences (allometric scaling):

4

Justification:

A default AF of 4 is used, according to ECHA REACH Guidance

AF for other interspecies differences:

1

Justification:

AF 1 used, no indication for differences in toxicokinetics and toxicodynamics

AF for intraspecies differences:

10

Justification:

A default AF of 10 is used, according to ECHA REACH Guidance

AF for the quality of the whole database:

1

Justification:

AF of 1 is appropriate: the database is comprehensive and of good quality

AF for remaining uncertainties:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Route of original study:

Oral

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

General Population - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

4.167 mg/kg bw/day

Most sensitive endpoint:

repeated dose toxicity

Route of original study:

Oral

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

240

Modified dose descriptor starting point:

NOAEL

Value:

1 000 mg/kg bw/day

Explanation for the modification of the dose descriptor starting point:

Data indicate a similar extent of absorption following oral and dermal exposure; correction for differences in the extent of absorption is not required.

AF for dose response relationship:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance. The use of a larger AF is not warranted on the basis of the data available.

AF for differences in duration of exposure:

6

Justification:

Starting point was extrapolated from a subacute to a chronic exposure period

AF for interspecies differences (allometric scaling):

4

Justification:

A default AF of 4 is used, according to ECHA REACH Guidance.

AF for other interspecies differences:

1

Justification:

AF 1 used, no indication for differences in toxicokinetics and toxicodynamics

AF for intraspecies differences:

10

Justification:

A default AF of 10 is used, according to ECHA REACH Guidance.

AF for the quality of the whole database:

1

Justification:

AF of 1 is appropriate: the database is comprehensive and of good quality.

AF for remaining uncertainties:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance.

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

General Population - Hazard via oral route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

4.167 mg/kg bw/day

Most sensitive endpoint:

repeated dose toxicity

Route of original study:

Oral

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

240

Modified dose descriptor starting point:

NOAEL

Value:

1 000 mg/kg bw/day

Explanation for the modification of the dose descriptor starting point:

Data indicate a similar extent of absorption following oral and dermal exposure; correction for differences in the extent of absorption is not required.

AF for dose response relationship:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance. The use of a larger AF is not warranted on the basis of the data available.

AF for differences in duration of exposure:

6

Justification:

Starting point was extrapolated from a subacute to a chronic exposure period

AF for interspecies differences (allometric scaling):

4

Justification:

A default AF of 4 is used, according to ECHA REACH Guidance.

AF for other interspecies differences:

1

Justification:

AF 1 used, no indication for differences in toxicokinetics and toxicodynamics

AF for intraspecies differences:

10

Justification:

A default AF of 10 is used, according to ECHA REACH Guidance.

AF for the quality of the whole database:

1

Justification:

AF of 1 is appropriate: the database is comprehensive and of good quality

AF for remaining uncertainties:

1

Justification:

A default AF of 1 is used, according to ECHA REACH Guidance.

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:

high hazard (no threshold derived)

Additional information - General Population

Toxicology summary

Toxicokinetics

MAA is a small, mobile, relatively volatile and uncharged molecule with excellent solubility in hydrophilic and hydrophobic solvents. It is rapidly and almost completely absorbed after oral exposure. Absorption via the dermis is comparatively lower which may also be due to the volatile behavior. MAA is rapidly excreted after hydrolysis of the ester function and also rapidly eliminated during metabolism. Tests with repeated dose administration demonstrate that outside lethal doses the effects of MAA are completely reversible. Cumulation in the body can be excluded.

Acute toxicity

Acute oral toxicity

The acute oral toxicity on rats was determined to be 2580 mg/kg.

Acute dermal toxicity

The acute dermal toxicity on rats was found to be > 2000 mg/kg.

Acute inhalation toxicity

Study not performed; dermal route was chosen instead.

Irritation/Corrosion

MAA was found to be non-irritating to skin and severely irritating to eyes, therefore the substance should be classified as severe eye-irritant - Category 1 (irreversible effect on the eye) according to Regulation (EC) No. 1272/2008.

Sensitisation

MAA is not a skin sensitiser.

Repeated dose toxicity

The appropriate dose levels were evaluated in a 7 -day-range-finding test. Based on this RF-study, dose levels of 0, 100, 300 and 1000 mg/kg b.w./day were fixed for the main study, including 2-weeks recovery for low and high dose groups. There were neither premature deaths nor clinical signs as a result of treatment with MAA. There were some minor effects observed on body weights, hematology, clinical chemistry, urinalysis, and organ weights. However, all these findings were either incidental or within the normal background range and therefore not considered to be of toxicological significance and treatment-related. There were also no necropsy and histological findings. In conclusion, in the absence of any effect, the NOEL and NOAEL were determined to be 1000 mg/kg/day.

Genetic toxicity

The test item MAA was tested for genetic toxicity in several in-vitro studies in 1988 and 1995, both with and without metabolic activation. A reverse mutation assay (Ames test) as well as a chromosomal aberration test were performed according to the corresponding OECD-guidelines. The Ames test used Salmonella typhimurium and E.coli strains and showed a negative result (non-mutagenic). An additional Ames test published in literature (JETOC no.43) showed a negative result as well and confirmed the non-mutagenic result of the first study.

The chromosomal aberration test performed with Chinese hamster ovary cells showed clastogenic effects. However, this clastogenic response at higher concentrations in presence of S9 -mix might be rather a secondary effect due to possible degradation products than a substance specific property. This assumption is confirmed by the additional experiment with pH-adjustment, where no clastogenic effects were observed up to 2500 microgr/ml. In another chromosomal aberration test performed in Japan and published in literature; this study was performed with pH-adjustment and showed a non-clastogenic result- confirming the assumption explained above.

Toxicity to reproduction

The study was performed according to OECD-guideline no. 422. MAA at dosages of 0 (vehicle control), 100, 300 and 1000 mg/kg/day was orally administered to Crj:CD(SD) male and female rats (12 animals/sex/group) from 14 days before mating through the mating period and up to the day before necropsy (Total: 35 days) in males and 14 days prior to mating through the gestation period up to day 3 of delivery in females to investigate the effect on the repeat dose and reproductive toxicity for the parent animals and the development for the offspring, and the following results were obtained.

Repeat dose toxicity:

There were some effects observed on the clinical signs, blood chemistry and some histopathological parameters. These changes were seen in single animals only, without dose dependency. Therefore, these findings were considered to be of incidental nature and not related to treatment with the test article. No effects were reported on the remaining parameters such as body weight, food consumption, hematology.

Reproductive/developmental toxicity:

As for reproductive performance in parent animal, no effects of administration of test article were observed on the estrus cycle, numbers of corpora lutea or implantations, copulation (mating performance) or fertility indices. Examination at delivery and during the lactation period revealed, no effects of administration of test article were observed on the gestational days, number of litter or live newborns, gestation, birth or stillbirth indices, sex ratio, body weight at birth or on day 4 after birth, viability index on day 4 after birth. No external malformations in live newborns were observed. As described above, the no observed effect level (NOEL) under this study conditions was assumed to be 1000 mg/kg/day for repeat dose toxicity in both males and females, and also to be 1000 mg/kg/day for reproductive/developmental toxicity in parent animals and offspring.