Reaction mass of 1-(2,6,6-trimethylcyclohex-2-en-1-yl)hepta-1,6-dien-3-one and 1-(2,6,6-trimethylcyclohex-1-en-1-yl)hepta-1,6-dien-3-one

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

6.2 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):

6

Dose descriptor starting point:

NOAEL

Value:

42 mg/kg bw/day

Modified dose descriptor starting point:

NOAEC

Value:

37 mg/m³

Explanation for the modification of the dose descriptor starting point:

Starting point is a NOAEL of 42 mg/kg bw. A factor 2 is applied for route to route extrapolation, oral to inhalation. 21 mg/kg * (1/0.38) * (6.7/10) = 37.0 mg/m3

AF for dose response relationship:

1

Justification:

No additional assessment factor for dose response is needed because the dosing was well spaced in the study and a NOAEL in the OECDTG422 study was derived (ECHA’s guidance, R.8.4.3.1, November, 2012).

AF for differences in duration of exposure:

2

Justification:

An assessment factor of 2 has been applied to extrapolate the NOAEL from sub-chronic to a chronic study as presented in R.8.4.3.1 and table R.8-5 (ECHA’s guidance, November, 2012)

AF for interspecies differences (allometric scaling):

1

Justification:

An assessment factor of 1 has been used because the difference in metabolic rate between rat and humans has been accounted for in the conversion of NOAEL in mg/kg bw to the NOAEC mg/m3, as presented in ECHA’s guidance R.8, figure R. 8-2 (November, 2012).

AF for other interspecies differences:

1

Justification:

Additional assessment factors for interspecies differences are not needed as has been derived in the ECETOC report (TR 110, 2010) based on a review of the scientific literature. The concept of adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. This analysis is based on a comparison of animal to actual human data that per se includes intraspecies variability in humans (see below at intraspecies differences).

AF for intraspecies differences:

3

Justification:

An assessment factor of 3 has been used to account for the intraspecies differences. This factor has been retrieved by ECETOC (TR110, 2010). The ECETOC analysis has been based on a comparison between animal and actual human data that per se includes intraspecies variability in humans. In addition, the human population under investigation comprised cancer patients; this represents a very sensitive subpopulation. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. Thus, this standard deviation represented by the GSD of 2.5-2.6 is probably due to potential differences in biological sensitivity between species, and includes intraspecies differences.

AF for the quality of the whole database:

1

Justification:

In accordance with ECHA Guidance on information requirements and chemical safety assessment – Chapter 8: Characterisation of dose [concentration]-response for human health, the evaluation of the total toxicological database should include an assessment whether the available information as a whole meets the tonnage driven data requirements necessary to fulfil the REACH requirements, or whether there are data gaps (completeness of the database). Furthermore, the hazard data should be assessed for the reliability and consistency across different studies and endpoints and taking into account the quality of the testing method, size and power of the study design, biological plausibility, dose-response relationships and statistical association (adequacy of the database). When taking into account the standard information requirements and the completeness and consistency of the database the default assessment factor of 1, to be applied for good/standard quality of the database, is recommended.

AF for remaining uncertainties:

1

Justification:

An assessment factor of 1 is applicable, because there are no remaining uncertainties, which have not already been accounted for.

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

DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

1.75 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):

24

Dose descriptor starting point:

NOAEL

Value:

42 mg/kg bw/day

Modified dose descriptor starting point:

NOAEL

Value:

42 mg/kg bw/day

Explanation for the modification of the dose descriptor starting point:

On the assumption that, in general, dermal absorption will not be higher than oral absorption, no default factor should be introduced when performing oral to dermal extrapolation.

AF for dose response relationship:

1

Justification:

No additional assessment factor for dose response is needed because the dosing was well spaced in the study and a NOAEL in the OECDTG422 study was derived (ECHA’s guidance, R.8.4.3.1, November, 2012).

AF for differences in duration of exposure:

2

Justification:

An assessment factor of 2 has been applied to extrapolate the NOAEL from sub-acute to a chronic study as presented in R.8.4.3.1 and table R.8-5 (ECHA’s guidance, November, 2012).

AF for interspecies differences (allometric scaling):

4

Justification:

For allometric scaling a factor of 4 is applicable to convert rat to human data. ECETOC (TR110, 2010), after a review of the scientific literature, concludes that adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans.

AF for other interspecies differences:

1

Justification:

Additional assessment factors for interspecies differences are not needed as has been derived in the ECETOC report (TR 110, 2010) based on a review of the scientific literature. The concept of adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. This analysis is based on a comparison of animal to actual human data that per se includes intraspecies variability in humans (see below at intraspecies differences).

AF for intraspecies differences:

3

Justification:

An assessment factor of 3 has been used to account for the intraspecies differences. This factor has been retrieved by ECETOC (TR 110, 2010) based on scientific literature. The ECETOC analysis has been based on a comparison between animal and actual human data that per se includes intraspecies variability in humans. In addition, the human population under investigation comprised cancer patients, which represents a very sensitive subpopulation. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. Thus, this standard deviation represented by the GSD of 2.5-2.6 is probably due to potential differences in biological sensitivity between species, and includes intraspecies differences.

AF for the quality of the whole database:

1

Justification:

In accordance with ECHA Guidance on information requirements and chemical safety assessment – Chapter 8: Characterisation of dose [concentration]-response for human health, the evaluation of the total toxicological database should include an assessment whether the available information as a whole meets the tonnage driven data requirements necessary to fulfil the REACH requirements, or whether there are data gaps (completeness of the database). Furthermore, the hazard data should be assessed for the reliability and consistency across different studies and endpoints and taking into account the quality of the testing method, size and power of the study design, biological plausibility, dose-response relationships and statistical association (adequacy of the database). When taking into account the standard information requirements and the completeness and consistency of the database the default assessment factor of 1, to be applied for good/standard quality of the database, is recommended.

AF for remaining uncertainties:

1

Justification:

An assessment factor of 1 is applicable, because there are no remaining uncertainties, which have not already been accounted for.

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

232 µg/cm²

Most sensitive endpoint:

sensitisation (skin)

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

1

Dose descriptor:

other: NOAEL

Value:

0.232 mg/m³

AF for dose response relationship:

1

Justification:

For the LLNA study an assessment factor of 1 is applicable, because 1) the NOAEL is used as a starting point; 2) the doses were well separated with a factor of 10 (0.1, 1, 10, and 100 %) and; 3) the dose response was (stimulation index was 0.9, 0.9, 10.4 and 17.5% respectively).

AF for differences in duration of exposure:

1

Justification:

An assessment factor of 1 is applicable, because the LLNA is considered to be sufficiently sensitive for assessing skin sensitization; 1) considering presence and absence of skin sensitization and; 2) determining a quantitative value for risk characterization (see note 17 in R.8, Application of AFs to the correct starting point to obtain the induction specific DNEL, page 125, 1st par).

AF for interspecies differences (allometric scaling):

1

Justification:

An assessment factor for allometric scaling is not needed because metabolic rates differences between mouse and human are not expected to be important for the skin sensitization of this substance, because the parent substance is causing the effect.

AF for other interspecies differences:

1

Justification:

An assessment factor for interspecies differences is not needed as according to ECHA Guidance R8 (2012) this applies to differences in toxicokinetic differences not related to metabolic rate and toxicodynamic differences. As skin sensitisation is a local effect caused by the parent compound differences in toxicokinetic and toxicodynamic properties are not important.

AF for intraspecies differences:

1

Justification:

The HRIPT test with Galbascone shows that healthy volunteers are 10 times less susceptible to sensitisation compared to the mice used in the test NOAEC is. Healthy volunteers are considered as sensitive as workers and therefore no assessment factor is needed.

AF for the quality of the whole database:

1

Justification:

An assessment factor for the quality of the database is not needed because a well-conducted LLNA guideline study is available

AF for remaining uncertainties:

1

Justification:

Assessment factor for remaining uncertainties is not needed. For vehicle effects: an assessment factor of 1 is applied as the matrices of the products compiled from the substance are not intended to enhance penetration. For type of skin (skin thickness and skin integrity) it can be seen that the skin of the back of the human volunteer and the skin of the mouse ear are considered sufficiently similar and more sensitive, respectively, compared to the exposed hands of the worker/consumer. Therefore an AF is not needed.

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:

no hazard identified

Additional information - workers

The DNELs for long term exposure (systemic effects) were derived in accordance with the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.8: Characterisation of dose [concentration]-response for human health with the exception of two assessment factors:

1.        Interspecies differences, remaining differences. For remaining differences it is considered that those already have been taken into account when applying an assessment factor for allometric scaling. The argumentation for this can be found in the ECETOC Guidance on Assessment Factors to Derive a DNEL (Technical Report No. 110, 2010). It is concluded that the concept of adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. This analysis is based on a comparison of animal to actual human data that per se includes intraspecies variability in humans. As the human population under investigation comprised cancer patients, this represents a very sensitive subpopulation. Thus, this additional’ variability represented by the GSD of 2.5-2.6 is probably due to not only potential differences in biological sensitivity between species, but also intraspecies differences. The intraspecies variability in humans is taken into account by the specific Assessment Factors for workers (3) and the general population (5). The introduction of the ‘remaining’ AF of 2.5 for interspecies variability would therefore mean an unjustified compilation of AF. Therefore, although ‘residual’ interspecies variability may remain following allometric scaling, this is largely accounted for in the default AF proposed for intraspecies variability, i.e. reflecting the interdependency of inter- and intraspecies AF.

2.        Intraspecies differences. The current proposed AF for intraspecies extrapolation of systemic effects for workers and the general population in the ECHA guidance differ from those proposed in the ECETOC guidance (2010). After studying both guidances it is concluded that the AF proposed by ECETOC are based on an evaluation of the scientific literature while the REACH TGD refers to standard default procedures. Therefore, the ECETOC guideline will be followed until the scientific basis for using an alternative approach has been established. This means that for workers instead of an AF of 5 as proposed in the ECHA guidance an AF of 3 will be used and for the general population instead of an AF of 10 and AF of 5.

 

ECETOC, 2010,http://www.ecetoc.org/wp-content/uploads/2014/08/ECETOC-TR-110-Guidance-on-assessment-factors-to-derive-a-DNEL.pdf

General Population - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

1.83 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):

10

Dose descriptor starting point:

NOAEL

Value:

42 mg/kg bw/day

Modified dose descriptor starting point:

NOAEC

Value:

18.3 mg/m³

Explanation for the modification of the dose descriptor starting point:

Starting point is a NOAEL of 42 mg/kg bw. A factor 2 is applied for route to route extrapolation, oral to inhalation. 21 mg/kg * (1/1.15) = 18.3 mg/m3

AF for dose response relationship:

1

Justification:

No additional assessment factor for dose response is needed because the dosing was well spaced in the study and a NOAEL in the OECDTG422 study was derived (ECHA’s guidance, R.8.4.3.1, November, 2012).

AF for differences in duration of exposure:

2

Justification:

An assessment factor of 2 has been applied to extrapolate the NOAEL from sub-chronic to a chronic study as presented in R.8.4.3.1 and table R.8-5 (ECHA’s guidance, November, 2012

AF for interspecies differences (allometric scaling):

1

Justification:

An assessment factor of 1 has been used because the difference in metabolic rate between rat and humans has been accounted for in the conversion of NOAEL in mg/kg bw to the NOEC mg/m3, as presented in ECHA’s guidance R.8, figure R. 8-2 (November, 2012).

AF for other interspecies differences:

1

Justification:

Additional assessment factors for interspecies differences are not needed as has been derived in the ECETOC report (TR 110, 2010) based on a review of the scientific literature. The concept of adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. This analysis is based on a comparison of animal to actual human data that per se includes intraspecies variability in humans (see below at intraspecies differences).

AF for intraspecies differences:

5

Justification:

An assessment factor of 5 has been used to account for the intraspecies differences as has been derived by ECETOC (TR110, 2010) based on a review of the scientific literature. The ECETOC analysis has been based on a comparison between animal and actual human data that per se includes intraspecies variability in humans. In addition, the human population under investigation comprised cancer patients, this represents a very sensitive subpopulation. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. Thus, this standard deviation represented by the GSD of 2.5-2.6 is probably due to potential differences in biological sensitivity between species, but includes intraspecies differences.

AF for the quality of the whole database:

1

Justification:

In accordance with ECHA Guidance on information requirements and chemical safety assessment – Chapter 8: Characterisation of dose [concentration]-response for human health, the evaluation of the total toxicological database should include an assessment whether the available information as a whole meets the tonnage driven data requirements necessary to fulfil the REACH requirements, or whether there are data gaps (completeness of the database). Furthermore, the hazard data should be assessed for the reliability and consistency across different studies and endpoints and taking into account the quality of the testing method, size and power of the study design, biological plausibility, dose-response relationships and statistical association (adequacy of the database). When taking into account the standard information requirements and the completeness and consistency of the database the default assessment factor of 1, to be applied for good/standard quality of the database, is recommended.

AF for remaining uncertainties:

1

Justification:

An assessment factor of 1 is applicable, because there are no remaining uncertainties, which have not already been accounted for.

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

DNEL related information

General Population - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

1.05 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):

40

Dose descriptor starting point:

NOAEL

Value:

42 mg/kg bw/day

Modified dose descriptor starting point:

NOAEL

Value:

42 mg/kg bw/day

Explanation for the modification of the dose descriptor starting point:

On the assumption that, in general, dermal absorption will not be higher than oral absorption, no default factor should be introduced when performing oral to dermal extrapolation.

AF for dose response relationship:

1

Justification:

No additional assessment factor for dose response is needed because the dosing was well spaced in the study and a NOAEL in the OECDTG422 study was derived (ECHA’s guidance, R.8.4.3.1, November, 2012).

AF for differences in duration of exposure:

2

Justification:

An assessment factor of 2 has been applied to extrapolate the NOAEL from sub-chronic to a chronic study as presented in R.8.4.3.1 and table R.8-5 (ECHA’s guidance, November, 2012).

AF for interspecies differences (allometric scaling):

4

Justification:

For allometric scaling a factor of 4 is applicable to convert rat to human data. ECETOC (TR110, 2010), after a review of the scientific literature, concludes that adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans.

AF for other interspecies differences:

1

Justification:

Additional assessment factors for interspecies differences are not needed as has been derived in the ECETOC report (TR 110, 2010) based on a review of the scientific literature. The value has been derived for systemic toxicity. In view of the systemic component of skin sensitisation the assessment factor can be used for skin sensitisation too.The concept of adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. This analysis is based on a comparison of animal to actual human data that per se includes intraspecies variability in humans (see below at intraspecies differences).

AF for intraspecies differences:

5

Justification:

An assessment factor of 5 has been used to account for the intraspecies differences. This factor has been retrieved by ECETOC (TR 110, 2010) based on scientific literature. The ECETOC analysis has been based on a comparison between animal and actual human data that per se includes intraspecies variability in humans. In addition, the human population under investigation comprised cancer patients, which represents a very sensitive subpopulation. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. Thus, this standard deviation represented by the GSD of 2.5-2.6 is probably due to potential differences in biological sensitivity between species, but includes intraspecies differences.

AF for the quality of the whole database:

1

Justification:

In accordance with ECHA Guidance on information requirements and chemical safety assessment – Chapter 8: Characterisation of dose [concentration]-response for human health, the evaluation of the total toxicological database should include an assessment whether the available information as a whole meets the tonnage driven data requirements necessary to fulfil the REACH requirements, or whether there are data gaps (completeness of the database). Furthermore, the hazard data should be assessed for the reliability and consistency across different studies and endpoints and taking into account the quality of the testing method, size and power of the study design, biological plausibility, dose-response relationships and statistical association (adequacy of the database). When taking into account the standard information requirements and the completeness and consistency of the database the default assessment factor of 1, to be applied for good/standard quality of the database, is recommended.

AF for remaining uncertainties:

1

Justification:

An assessment factor of 1 is applicable, because there are no remaining uncertainties, which have not already been accounted for.

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

116 µg/cm²

Most sensitive endpoint:

sensitisation (skin)

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

2

Dose descriptor:

other: NOAEL

Value:

0.232 mg/m³

AF for dose response relationship:

1

Justification:

For the LLNA study an assessment factor of 1 is applicable, because 1) the NOAEL is used as a starting point; 2) the doses were well separated with a factor of 10 (0.1, 1, 10, and 100 %) and; 3) the dose response was (stimulation index was 0.9, 0.9, 10.4 and 17.5% respectively).

AF for differences in duration of exposure:

1

Justification:

An assessment factor of 1 is applicable, because the LLNA is considered to be sufficiently sensitive for assessing skin sensitization; 1) considering presence and absence of skin sensitization and; 2) determining a quantitative value for risk characterization (see note 17 in R.8, Application of AFs to the correct starting point to obtain the induction specific DNEL, page 125, 1st par).

AF for interspecies differences (allometric scaling):

1

Justification:

An assessment factor for allometric scaling is not needed because metabolic rates differences between mouse and human are not expected to be important for the skin sensitization of this substance, because the parent substance is causing the effect.

AF for other interspecies differences:

1

Justification:

An assessment factor for interspecies differences is not needed as according to ECHA Guidance R8 (2012) this applies to differences in toxicokinetic differences not related to metabolic rate and toxicodynamic differences. As skin sensitisation is a local effect caused by the parent compound differences in toxicokinetic and toxicodynamic properties are not important.

AF for intraspecies differences:

2

Justification:

The general population is circa 2 times more vulnerable compared to healthy volunteers and therefore an assessment factor 2 is applied , which is in accordance with the ECHA guidance.

AF for the quality of the whole database:

1

Justification:

An assessment factor for the quality of the database is not needed because a well-conducted LLNA guideline study is available.

AF for remaining uncertainties:

1

Justification:

Assessment factor for remaining uncertainties is not needed. For vehicle effects: an assessment factor of 1 is applied as the matrices of the products compiled from the substance are not intended to enhance penetration. For type of skin (skin thickness and skin integrity) it can be seen that the skin of the back of the human volunteer and the skin of the mouse ear are considered sufficiently similar and more sensitive, respectively, compared to the exposed hands of the worker/consumer. Therefore an AF is not needed.

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:

1.05 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):

40

Dose descriptor starting point:

NOAEL

Value:

42 mg/kg bw/day

AF for dose response relationship:

1

Justification:

No additional assessment factor for dose response is needed because the dosing was well spaced in the study and a NOAEL in the OECDTG422 study was derived (ECHA’s guidance, R.8.4.3.1, November, 2012).

AF for differences in duration of exposure:

2

Justification:

An assessment factor of 2 has been applied to extrapolate the NOAEL from sub-acute to a chronic study as presented in R.8.4.3.1 and table R.8-5 (ECHA’s guidance, November, 2012).

AF for interspecies differences (allometric scaling):

4

Justification:

For allometric scaling a factor of 4 is applicable to convert rat to human data. ECETOC (TR110, 2010), after a review of the scientific literature, concludes that adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans.

AF for other interspecies differences:

1

Justification:

Additional assessment factors for interspecies differences are not needed as has been derived in the ECETOC report (TR 110, 2010) based on a review of the scientific literature. The concept of adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. This analysis is based on a comparison of animal to actual human data that per se includes intraspecies variability in humans (see below at intraspecies differences).

AF for intraspecies differences:

5

Justification:

An assessment factor of 5 has been used to account for the intraspecies differences. This factor has been retrieved by ECETOC (TR 110, 2010) based on scientific literature. The ECETOC analysis has been based on a comparison between animal and actual human data that per se includes intraspecies variability in humans. In addition, the human population under investigation comprised cancer patients, which represents a very sensitive subpopulation. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. Thus, this standard deviation represented by the GSD of 2.5-2.6 is probably due to potential differences in biological sensitivity between species, but includes intraspecies differences.

AF for the quality of the whole database:

1

Justification:

In accordance with ECHA Guidance on information requirements and chemical safety assessment – Chapter 8: Characterisation of dose [concentration]-response for human health, the evaluation of the total toxicological database should include an assessment whether the available information as a whole meets the tonnage driven data requirements necessary to fulfil the REACH requirements, or whether there are data gaps (completeness of the database). Furthermore, the hazard data should be assessed for the reliability and consistency across different studies and endpoints and taking into account the quality of the testing method, size and power of the study design, biological plausibility, dose-response relationships and statistical association (adequacy of the database). When taking into account the standard information requirements and the completeness and consistency of the database the default assessment factor of 1, to be applied for good/standard quality of the database, is recommended.

AF for remaining uncertainties:

1

Justification:

An assessment factor of 1 is applicable, because there are no remaining uncertainties, which have not already been accounted for.

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:

no hazard identified

Additional information - General Population

The DNELs for long term exposure (systemic effects) were derived in accordance with the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.8: Characterisation of dose [concentration]-response for human health with the exception of two assessment factors:

1.        Interspecies differences, remaining differences. For remaining differences it is considered that those already have been taken into account when applying an assessment factor for allometric scaling. The argumentation for this can be found in the ECETOC Guidance on Assessment Factors to Derive a DNEL (Technical Report No. 110, 2010). It is concluded that the concept of adjusting animal dose by allometric scaling predicts reasonably well the appropriate dose in humans. A Geometric Standard Deviation (GSD) of 2.5-2.6 suggests the likelihood of some variability or additional uncertainty around the predicted NOAEL in humans. This analysis is based on a comparison of animal to actual human data that per se includes intraspecies variability in humans. As the human population under investigation comprised cancer patients, this represents a very sensitive subpopulation. Thus, this additional’ variability represented by the GSD of 2.5-2.6 is probably due to not only potential differences in biological sensitivity between species, but also intraspecies differences. The intraspecies variability in humans is taken into account by the specific Assessment Factors for workers (3) and the general population (5). The introduction of the ‘remaining’ AF of 2.5 for interspecies variability would therefore mean an unjustified compilation of AF. Therefore, although ‘residual’ interspecies variability may remain following allometric scaling, this is largely accounted for in the default AF proposed for intraspecies variability, i.e. reflecting the interdependency of inter- and intraspecies AF.

2.        Intraspecies differences. The current proposed AF for intraspecies extrapolation of systemic effects for workers and the general population in the ECHA guidance differ from those proposed in the ECETOC guidance (2010). After studying both guidances it is concluded that the AF proposed by ECETOC are based on an evaluation of the scientific literature while the REACH TGD refers to standard default procedures. Therefore, the ECETOC guideline will be followed until the scientific basis for using an alternative approach has been established. This means that for workers instead of an AF of 5 as proposed in the ECHA guidance an AF of 3 will be used and for the general population instead of an AF of 10 and AF of 5.

 

ECETOC, 2010,http://www.ecetoc.org/wp-content/uploads/2014/08/ECETOC-TR-110-Guidance-on-assessment-factors-to-derive-a-DNEL.pdf