p-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.35 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):

12.5

Dose descriptor starting point:

NOAEL

Value:

5 mg/kg bw/day

Modified dose descriptor starting point:

NOAEC

Value:

4.41 mg/m³

Explanation for the modification of the dose descriptor starting point:

A read across approach is in place for this substance (m-isomer) and

p-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline (p-isomer). For full details, please see the Read Across Approch Justification document enclosed in Chapter 13.

A two-generation reproduction study has been conducted at doses of 5, 15 and 25 mg/kg using the p-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline isomer. The results of this test indicated that the 5 mg/kg bw/day was the No Observed Effect Level (NOEL) for the repeated administration of the test item on reproduction, pre-natal development and post-natal development of the rat when administered over two successive generations. The next highest dose was 15 mg/kg bw/d and provided the LOEL. As noted during the conduct of the prenatal developmental study irritation of the GI tract was observed at doses 15 mg/kg bw/day (15 and 25 mg/kg bw/d) and this indicates that there is a clear threshold dose whereby the primary toxicity response is associated with the effects on the gastrointestinal tract (duodenum and stomach).

During the conduct of the two-generation reproduction study with the p-(2,3-epoxypropoxy)- N,Nbis(2,3-epoxypropyl)aniline isomer the following effects were identified in animals treated with 15 mg/kg bw d.

• Degeneration/atrophy of the glandular mucosa (minimal to moderate) of the stomach

• Degeneration/atrophy of the mucosa (minimal to mild) and regenerative hyperplasia of

the mucosa (minimal to mild) of the duodenum

• Regenerative hyperplasia of the mucosa (minimal) of the Jejunum

As a result of the effects described above it is proposed that 15 mg/kg bw d represents a clear threshold dose for the mature animals and severe effects on the gastrointestinal tract which subsequently leads to a detrimental health status on the animals. At a dose of 5 mg/kg bw d the

following effects were identified:

• P0 Parental liver weight

• Pituitary weight P0 females

• Prostate gland weight (F1)

• Epididymis weight (F1)

• Kidney weight (F1)

• Testes Weight (F1)

• Seminal vesicle weight (F1)

Only two out of the seven endpoints described above are identified in the parental animals and the remaining five are relevant to the F1 offspring. It is proposed that the effects on liver weight and pituitary weight in the P0 generation reflects first pass metabolism becoming saturated due to the length of the exposure regime to high dose levels tested (350 mg per day based on 70kg human equivalent, which is completely unfeasible based on the proposed industrial applications/uses). Using this argumentation, there is no surprise that younger F1 animals are more susceptible and that there is a manifestation of sublethal effects..

It is proposed that the use of either 5 or 15 mg/kg bw d could be considered as the NOEL for risk assessment purposes. The effects identified at 5 mg/kg bw d in F1 animals are the consequence of parental animals with compromised health status e.g. pituitary and liver weight changes are both classic signs of metabolism systems under stress. Whilst 15 mg/kg bw d would be protective and suitable for industrial applications currently registered it is suggested that a conservative DNEL is derived using a NOEL of 5 mg/kg bw d.

Hazard identification

The extensive data set for p-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline and m-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline clearly presents the toxicological cascade of effects following exposure. At doses greater than 15 mg/kg bw d combined with repeated and reproductive test duration animals are clearly compromised by the effects on saturated metabolism pathways which leads to apical endpoints of irritation, corrosion and ulceration of the of the gastrointestinal epithelia (Annex 1 Read Across). At a reduced dose of 5 mg/kg bw d combined with repeated and reproductive test durations there is insufficient dose and time available to overwhelm and cause damage to the gastrointestinal tract but the lower dose and same timescale are sufficient to identify that first pass metabolic systems are under significant stress which is represented by changes in pituitary and liver weights. An Adverse Outcome Pathway has been proposed in Annex 2 of Read Across).

Risk Characterisation

It should not be ignored that sensitizing properties were identified following exposure to both, p-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline and m-(2,3-epoxypropoxy)- N,N-bis(2,3-epoxypropyl)aniline , both substances are classified as category 1A sensitizers and fall within the “High hazard band” of ECHAs Part E guidance: Risk Characterisation Guidance (Table E. 3.1). The prescribed protection for tackling sensitization creates an overarching “hazard umbrella” i.e. potential for exposure needs to be eliminated. This “hazard umbrella”, the relevant risk management measures and personal protective equipment requirements effectively eliminates the need for quantitative risk assessment and the relevance of any NOEL/DNEL values derived via the repeat dose or reproduction studies.

Parental seminal vesicle, testes and epididymis and spleen weights most sensitive endpoints at 15 mg/kg bw d although it should be noted that the following effects were also present at 15 mg/kg bw d Degeneration/atrophy of the mucosa (minimal to mild) duodenum Regenerative hyperplasia of the mucosa (minimal to mild) duodenum and therefore at doses equal to or greater than 15 mg/kg bw d irritation/corrosion to the gastrointestinal tract is the primary toxicological response and all other effects are due to the health status of the exposed animals.

A conservative approach has been used and the NOAEL of 5 mg/kg bw d used for risk characterisaion.

The oral endpoint of 5 mg/kg bw d has been converted to an NOAEC as follows:

5/2 / 0.38 = Inhalation NOAEL of 6.57 mg/m3 (8h) NOAEC = 6.57 x 0.67 = 4.40 mg/m 3

The REACH Guidance on information requirements and chemical safety assessment (R.8.4.2) prescribes a default factor of 2 in case of oral to inhalation extrapolation. Standard respiratory volume of a rat, corrected for 8 h exposure, as proposed in the REACH Guidance on information requirements and chemical safety assessment (R.8.4.2)

AF for dose response relationship:

1

Justification:

Oral endpoint is derived from a chronic oral 2-generation reproductive study and therefore an assessment factor for duration is not neccessary as per ECHA Guidance on Information Requirements and Chemical Safety Assessment Chapter R8, Table R8-5

AF for other interspecies differences:

2.5

Justification:

Remaining differences

AF for intraspecies differences:

5

Justification:

Default assessment factor workers for threshold effects based on the fact that this sub-population does not include the very young, very old or very ill.

AF for the quality of the whole database:

1

Justification:

Studies conducted to OECD guidelines and fully GLP

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Explanation for the modification of the dose descriptor starting point:

According to the REACH guideline (R8, Appendix R 8-8), a DNEL for acute toxicity should be derived if an acute toxicity hazard (leading to C&L) has been identified and there is a potential risk for high peak exposures. The substance is classified for acute oral toxicity, however the DNELs derived for long term exposure are considered to be sufficient for protection of the workers, therefore no short-term DNELs are derived for these routes of exposure. The substance is also as skin sensitizing but no DNELs could be derived. No data is available whether the test substance could cause irritation to the respiratory track and therefore no DNEL could be derived.

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:

0.1 mg/kg bw/day

Most sensitive endpoint:

effect on fertility

Route of original study:

Oral

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

50

Dose descriptor starting point:

NOAEL

Value:

5 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 is introduced for the oral to dermal extrapolation. The REACH Guidance on information requirements and chemical safety assessment (R.8.4.2) prescribes a default factor of 1 in case of oral to dermal extrapolation.

AF for dose response relationship:

1

Justification:

Assessment factor is not required, the NOAEL is derived using a chronic 2-generation reproduction study as per ECHA guidance on Risk Assessment Chapter R8

AF for interspecies differences (allometric scaling):

4

Justification:

Allometric scaling default AF (4) to allow for differences in metabolic rate. Species specific information is available therefore a further AF for remaining differences is not relevant as according to Section R.8.4.3.3 of the REACH guidance on information requirements and chemical safety assessment

AF for other interspecies differences:

2.5

Justification:

Remaining differences

AF for intraspecies differences:

5

Justification:

Default assessment factor workers for threshold effects based on the fact that this sub-population does not include the very young, very old or very ill.

AF for the quality of the whole database:

1

Justification:

GLP and OECD guideline study

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

high hazard (no threshold derived)

Most sensitive endpoint:

sensitisation (skin)

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

According to the REACH Guidance on information requirements and chemical safety assessment, a leading DN(M)EL needs to be derived for every relevant human population and every relevant route, duration and frequency of exposure, if feasible. 

Short-term toxicity:

According to the REACH guideline (R8, Appendix R 8-8), a DNEL for acute toxicity should be derived if an acute toxicity hazard (leading to C&L) has been identified and there is a potential risk for high peak exposures. Since the substance is not classified for acute dermal and inhalation, no short-term DNELs needs to be derived for these routes of exposure.

Additionally long-term DNELs are normally sufficient to ensure that effects do not occur and to protect workers, if long term DNELs are maintained.

Skin sensitisation:

The substance is considered to a skin sensitizer and classified Skin sens. Cat 1A.

Long-term toxicity:

A chronic oral 2 -generation reproduction study in the rat is available, A NOAEL of 25 mg/kg bw was determined for systemic toxicity.

A sub-chronic 90day repeat dose oral study in the rat is available, a NOAEL of 15mg/kg bw/d was determined for systemic toxicity.

Hazard identification

The extensive data set for p-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline (MY0500) m-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline (MY0600) clearly presents the toxicological cascade of effects following exposure.

At doses greater than ≥15 mg/kg bw d combined with repeated and reproductive test durations animals are clearly compromised by the effects on saturated metabolism pathways which leads to apical endpoints of irritation, corrosion and ulceration of the of the gastrointestinal epithelia (Annex 1). At a reduced dose of 5 mg/kg bw d combined with repeated and reproductive test durations there is insufficient dose and time available to overwhelm and cause damage to the gastrointestinal tract but the lower dose and same timescale are sufficient to identify that first pass metabolic systems are under significant stress which is represented by changes in pituitary and liver weights. An Adverse Outcome Pathway has been proposed in Annex 2.

Risk Characterisation

It should not be ignored that sensitizing properties were identified following exposure to both, p-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline (MY0500) m-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline (MY0600), both substances are classified as category 1A sensitizers and fall within the “High hazard band” of ECHAs Part E guidance: Risk Characterisation Guidance (Table E. 3.1). The prescribed protection for tackling sensitization creates an overarching “hazard umbrella” i.e. potential for exposure needs to be eliminated. This “hazard umbrella”, the relevant risk management measures and personal protective equipment requirements effectively eliminates the need for quantitative risk assessment and the relevance of any NOEL/DNEL values derived via the repeat dose or reproduction studies.

Conclusion on toxicological properties

Regarding systemic toxicity, the comparison of the endpoints derived from the acute oral and dermal studies in rats on the m- and p-isomers identifies synonymous toxicity thresholds. Similarities in the systemic signs of toxicity as well as in the local effects were observed during the acute, repeated dose and pre-natal studies for the m- and p-isomers, suggesting a similar mode of action after oral ingestion. After oral repeated exposure, the m-isomer showed systemic signs of toxicity that were also noted in the acute studies for both substances. The high reactivity of the epoxide groups on DNA- and protein-binding again are responsible for toxicity effects. Again, the detoxification process mainly occurs via the epoxide hydrolase enzyme. The epoxide hydrolases are a class of proteins that catalyze the hydration of chemically reactive epoxides to their corresponding dihydrodiol products. Simple epoxides are hydrated to their corresponding vicinal dihydrodiols, and arene oxides to trans-dihydrodiols. In general, this hydration leads to more stable and less reactive intermediates that can be readily conjugated and excreted via the urine. However, at excessive doses ≥15 mg/kg bw d the first pass metabolism system becomes saturated and generates excessive H+ which returns to the duodenum

via the enterohepatic circulation resulting in irritation, corrosion and ulceration of the epithelia.

Considering that both substances are structural isomers, that the critical functional group for toxicity being the epoxide groups is present equally presents in both substances, we assume that the detoxification process occurring with the epoxide hydrolase will occur for both substances and in the same manner in repeated toxicity studies, as well as in other mammalian toxicity endpoints like reproductive toxicity, but due to the lower viscosity of the p-(2,3-epoxypropoxy)- N,N-bis (2,3-epoxypropyl)aniline (MY0500) it is expected to be more dispersed which will improve bioaccessibility.

Whilst the detoxification pathway and first pass metabolism of the two isomers is expected to be the same the data from the pre-natal developmental studies indicate a slightly higher toxicity associated with the MY0500 isomer compared to the MY0600. This difference is expected to be an artefact resulting from the higher viscosity of the MY0600 isomer which leads to a decrease in dissolution rate which is likely to minimise and localise the irritating primary site of contact effects of the MY0600 isomer on the gastrointestinal tract when compared to the MY0500 isomer which will become more widely dispersed following the oral gavage dosing, subsequently the higher dispersion of the MY0500 isomer will increase uptake rate via a larger surface area from the duodenum to the gastroduodenal and superior pancreatic duodenal arteries and transport to the liver. This argumentation for the difference in toxicity resulting from the difference is viscosity is further supported Levy and Jusko (1965)1 who investigated the effect of viscosity on the absorption rate of two model drugs (ethanol and salicylic acid) from the stomach of rats. The experiments were designed to allow recognition of possible effects due to complex formation and evaluation of the effect of viscosity on (a) the rate of movement of drug molecules to the absorbing membranes and (b) the rate of gastrointestinal transit of the solutions. It was found that both a and b were decreased with increasing viscosity.

Based on the similarity of structure and chemical functionality, as well as on the above-mentioned experimental results confirming that both the m- and p-isomer substances have the same toxicological profile and the fact that the lower viscosity of the MY0500 isomer facilitates toxicity and therefore can be considered protective of exposure to the MY0600 isomer the read-across approach proposed is justified.

Since chronic oral toxicity studies are available a route-to-route extrapolation is needed to derive the DNELs for dermal and inhalation route.According to Chapter R.8 of REACH Guidance on information requirements and chemical safety assessment, it is proposed in the absence of route-specific information on the starting route, to include a default factor of 2 in the case of oral-to-inhalation extrapolation. On the assumption that, in general, dermal absorption will not be higher than oral absorption, no default factor is introduced for the oral to dermal extrapolation. The REACH Guidance on information requirements and chemical safety assessment (R.8.4.2) prescribes a default factor of 1 in case of oral to dermal extrapolation. This approach will be taken forward to DNEL derivation.

General Population - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

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:

no hazard identified

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:

no hazard identified

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