Cyclohex-1,2-ylenediamine

Toxicological Summary

Workers - 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:

DNEL (Derived No Effect Level)

Value:

0.27 mg/m³

Most sensitive endpoint:

irritation (respiratory tract)

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Dose descriptor:

LOAEC

Justification:

starting point is LOAEC instead of NOAEC

Justification:

no additional factor is required for time duration since the effect observed is not dependent on the time of exposure

Justification:

no allometric scaling foreseen

Justification:

no deficiencies

Acute/short term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.53 mg/m³

Most sensitive endpoint:

irritation (respiratory tract)

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

DNEL extrapolated from long term DNEL

Workers - 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:

high hazard (no threshold derived)

Most sensitive endpoint:

skin irritation/corrosion

Acute/short term exposure

Hazard assessment conclusion:

high hazard (no threshold derived)

Most sensitive endpoint:

skin irritation/corrosion

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:

high hazard (no threshold derived)

Additional information - workers

1    Short overview of substance specific data to be considered for DCH

Inhalation and dermal exposure are the most appropriate route for assessing occupational risk in workers. Effects from exposure of animals to DCH via the inhalation route are limited to the upper respiratory tract (larynx and nasal passages) caused by important local irritation.

Some sort of general systemic toxicity was observed in an OECD 408 study (90-day exposure via oral gavage), but more importantly effects on the male reproduction system were identified leading to classification for reproduction toxicity (fertility). As this study leads to the most conservative NOAEL regarding studies using the oral application route and showing systemic effects, this NOAEL is used as basis for a derivation for a long-term inhalation DNEL for workers covering systemic effects and compare it to the DNEL for local effects derived from studies with inhalation exposure.

In an OECD 422 study female Wistar rats were exposed via oral gavage to DCH and showed clear maternal systemic toxicity at the high dose level. There were also effects related to reproduction (decreased gestation index) and litter observation (reduced average and total number of living pups) that were considered to be an effect of treatment. An increased incidence of postnatal loss (due to cannibalism and missing pups) was observed for all treated groups when compared to control, however no dose response relationship could be established.

A newly performed OECD 414 study in Wistar rats (exposure on GD6 to GD20 via oral gavage) ruled out direct developmental toxic effects of the submission substance. At the high dose maternal animals showed drastically reduced body weight gains and food intake which resulted in increased incidences of skeletal abnormalities in the offspring (secondary to maternal toxicity), while only reduction of overall body weight gain was observed at mid dose level and no adverse developmental effects were noted in the pups.

Tests assessing the mutagenic potential of DCH in vitro provided no sufficient evidence for classification as germ cell mutagenic. The positive results from a newly performed AMES test will be further investigated using appropriate in vivo methods.

2  DNELs/DMELs derivation according to the toxicological profile of DCH

For the dermal route no DNELs were derived as DCH is classified as corrosive. Considering these data, it is very difficult to derive a threshold and to set a DNEL. Hence, only qualitative assessment can be performed following the approach described in the dossier to define the risk management measures (RMMs) and operational conditions (OCs).

 

Worker-DNEL long-term for inhalation route- local effects:

In a subacute inhalation toxicity study 10 male rats were exposed via inhalation for 6 hours per day, 5 times a week for two weeks to an aerosol/vapour mixture containing test material in concentrations of 0, 10, 49 and 240 mg/m³ (analytical concentration). There were no adverse effects observed in any of the test groups with respect to the haematologic, clinical chemical, urinalysis, and body weight parameters measured. As expected from its chemical basicity, inhaled test material produced respiratory tract irritation in exposed rats. However, the lesions (inflammation/necrosis) observed occurred only in the upper respiratory tract (mainly the nose, larynx, and pharynx), were moderate at the highest concentration tested, and were decreased in severity at the lower test concentrations. Effects observed in the 49 mg/m³ group were mainly mild and those in the 10 mg/m³ group were minimal. The observed effects were completely reversible after a two-week recovery period even at the 240 mg/m³ concentration. Although a no-adverse-effect concentration could not be determined in this study, the respiratory tract effects observed at the lowest tested concentration (10 mg/m³) were considered minimal and reversible and therefore considered as LOAEC.

The results of this study were confirmed using another amine which is structurally related to the registration substance. This amine, i.e., namely 2-methylpentamethylene-1,5-diamine (MPMD, CAS 15520-10-2), is another C6-diamine but branched instead of cyclic as DCH. In a study with the same study design (10 times à 6-hour exposure of rats during a 14-day period) using MPMD as test material comparable local effects were observed in all treated groups thus yielding also a LOAEC of 9.2 mg/m³.

Furthermore, there is experimental evidence from a sub-chronic study with Hexamethylenediamine dihydrochloride (HDDC = salt of Hexamethylenediamine (HMD, CAS 124-09-4)). HMD is another C6-diamine but linear instead of cyclic as DCH or branched as MPMD. In this study with inhalation exposure of rats (6h/day, 5d/week for 13 weeks) also local respiratory effects were identified as critical. Under the test conditions, the NOAEC (HDDC) = 16 mg/m³/day for local respiratory damage (nasal respiratory epithelium degeneration), corresponding to a NOAEC (HMD) = 10 mg/m³/day. In another sub-chronic inhalation toxicity study with rats, the animals were repeatedly exposed to aqueous HMD aerosol for six hours per day, five days per week at mean analytical concentrations of 0, 12.8, 51 and 215 mg/m³. Under the test conditions, no systemic effects were observed related to the treatment with HMD. The significant local irritation of respiratory tract, inducing clinical signs, was observed at the two highest concentrations tested. The NOAEC in male and female rats exposed by whole-body inhalation was 12.8 mg HMD/m³.

Only one study is available using the submission substance. Thus, the LOAEC of the study will serve as starting point for the DNEL derivation. However, the experimental data on related amines serves as supporting evidence for verifying the local irritating nature of amines in general. Especially the sub-chronic studies with HMD and HMD-dihydrochloride verify that the effect is not crucially time dependent either - therefore no assessment factor was used for differences in duration of exposure.

 

DNEL derivation:

Basis LOAEC: 10 mg/m³ from 14 days toxicity study after aerosol/vapour exposure

Effects: dose dependent effects seen on the upper respiratory tract (e. g. nasal lesions) which were from minimal to moderate severity and were reversible within the 14-day recovery period

No correction of LOAEC was performed as local irritating effects are concentration dependent and are independent of the absorbed dose.

Assessment factors:

• Interspecies differences:          no allometric scaling, 2.5 (remaining differences)


• Intraspecies differences:      5


• Differences in duration of exposure:            1 (no additional factor is required for exposure duration since the effect observed is not dependent on the time of exposure))


• Issues related to dose-response:               3 (starting point is LOAEC instead of NOAEC)


• Quality of whole database:        1 (no deficiencies)

--> Overall assessment factor: 37.5

DNEL = 10 mg/m³/37.5

DNEL = 266 µg/m³ = 0.266 mg/m³ ≈ 0.27 mg/m³

 

Worker-DNEL short-term for inhalation route- local effects:

As an acute toxicity hazard has been identified (leading to C&L, i.e. STOT Single Exp. 3 (H335)) a DNEL for peak exposure has to be derived. Ideally sub-lethal toxicity should be the starting point rather than mortality. In our case from the acute inhalation toxicity study only information on mortality could be extracted as there were no detailed descriptions on pathological findings included. Therefore repeated-dose data from the sub-acute inhalation study with the submission substance is thought to better characterize the acute hazard originating from the toxicological profile of the substance.

Effects after repeated application of the submission substance by inhalation to rats were restricted to the respiratory tract. Therefore, an acute DNEL inhalation for local effects was established from the WORKER DNEL LONG-TERM FOR INHALATION ROUTE, LOCAL EFFECTS by using a multiplying factor of 2 considering that the observed adverse effects are mainly driven by the exposure concentration of the submission substance with respect to its corrosive properties.

 

DNEL: 266 µg/m³ *2 = 532 µg/m³ = 0.53 mg/m³

 

Below, the DNEL derivation for local and systemic effects are compared to evaluate which of the effects leads to the more conservative assessment. As systemic effects were only observed after oral exposure route-to-route extrapolation has to be performed. The study which identified the lowest NOAEL was used.

(Please note: The higher NOAELs identified in the OCED 422 and 414 study would lead to comparable DNELs for systemic effects as calculated below for the descriptor of the 90-day study. This is due to shorter exposure durations and thus the higher time extrapolation factors that have to be applied.)

Workers long-term DNEL inhalation	Local	Systemic
Step a: determination of dose-descriptor
Key study	HLR 555-93, no OECD Guideline	Labcorp 2022, OECD 408
Relevant dose descriptor	LOAEC = 10 mg/m^3for local irritant effects of the upper respiratory tract in rats	NOAEL = 50 mg/kg bw/day (systemic effects on male reproduction system, male fertility classification)
Step b: correct starting point		*
Differences in metabolic rate per b.w. (allometric scaling)	- (local effects)	4 (rat)
Differences in absorption depending on route of exposure (route-route extrapolation, human/animal)	-       - (local effects)	-     2 (worst case assumption according to ECHA guidance R.8: 50% oral and 100% inhalation exposure)
Modification for exposure (experiment and human)	-       - (local irritant effects depending on concentration, only)	-      - (daily dose)
Modification for respiratory volume	-	X 70 kg bw / 10 m³ respirator volume per work shift
Correct starting point = relevant dose descriptor / overall factor for uncertainties	10 mg/m³	43.75 mg/m³
Step c : assessment factors
Interspecies differences	2.5 (effects on respiratory tract)	2.5 (remaining differences)
Intraspecies differences	5	5
Duration extrapolation (sub-acute/sub-chronic/chronic)	1 (no additional factor is required for exposure duration since the effect observed is not dependent on the time of exposure)	2 (subchronic to chronic)
Issues related to dose-response	3 (LOAEC)	1
Quality of whole database	1	1
Overall assessment factor	37.5	25
DNEL calculation	0.266 mg/m³	1.75 mg/m³

* Please note this is one of the ways shown in ECHA Guidance on information requirements and chemical safety assessment Chapter R.8, APPENDIX R. 8-2, Example R. 8-2 Workers (or Figure R. 8-3) for correction of the starting point. This is not the preferred way, but here differences from the local DNEL derivation can be pointed out. The preferred way (i.e. 50 mg/kg bw/day / 0.38 m³/kg bw * 50% / 100%* 6.7 m³ / 10 m³) leads to the same numerical value.

Final conclusion:

The inhalation workers DNEL long-term calculated for local effects is 0.266 mg/m³ ≈ 0,27 mg/m³ compared to 1.75 mg/m³ for systemic effects. The lower DNEL for local effects is considered to be protective also regarding systemic effects and taken forward for risk characterisation.

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:

DNEL (Derived No Effect Level)

Value:

0.13 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Dose descriptor:

LOAEC

Justification:

starting point is LOAEC instead of NOAEC

Justification:

no additional factor is required for time duration since the effect observed is not dependent on the time of exposure

Justification:

no deficiencies

Acute/short term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.27 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

DNEL extrapolated from long term DNEL

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:

high hazard (no threshold derived)

Most sensitive endpoint:

skin irritation/corrosion

Acute/short term exposure

Hazard assessment conclusion:

high hazard (no threshold derived)

Most sensitive endpoint:

skin irritation/corrosion

General Population - Hazard via oral route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.25 mg/kg bw/day

Most sensitive endpoint:

repeated dose toxicity

Route of original study:

Oral

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Modified dose descriptor starting point:

NOAEL

Value:

50 mg/kg bw/day

Justification:

subchronic to chronic

Justification:

no deficiencies

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

1  DNELs/DMELs derivation according to the toxicological profile of DCH

The general population includes consumers and humans exposed via the environment. Consumer exposure is not expected as DCH has no consumer use. But exposure of human via the environment is of potential concern. Inhalation and oral exposure were the most appropriate route for assessing risks for human exposed via the environment.

General population-DNEL long-term for inhalation route- local effects:

In a subacute inhalation toxicity study 10 male rats were exposed via inhalation for 6 hours per day, 5 times a week for two weeks to an aerosol/vapour mixture containing test material in concentrations of 0, 10, 49 and 240 mg/m³ (analytical concentration). There were no adverse effects observed in any of the test groups with respect to the haematologic, clinical chemical, urinalysis, and body weight parameters measured. As expected from its chemical basicity, inhaled test material produced respiratory tract irritation in exposed rats. However, the lesions (inflammation/necrosis) observed occurred only in the upper respiratory tract (mainly the nose, larynx, and pharynx), were moderate at the highest concentration tested, and were decreased in severity at the lower test concentrations. Effects observed in the 49 mg/m³ group were mainly mild and those in the 10 mg/m³ group were minimal. The observed effects were completely reversible after a two-week recovery period even at the 240 mg/m3 concentration. Although a no-adverse-effect concentration could not be determined in this study, the respiratory tract effects observed at the lowest tested concentration (10 mg DCH/m³) were considered minimal and reversible and therefore considered as LOAEC.

The results of this study were confirmed using another amine which is structurally related to the registration substance. This amine, i.e., namely 2-methylpentamethylene-1,5-diamine (MPMD, CAS 15520-10-2), is another C6-diamine but branched instead of cyclic as DCH. In a study with the same study design (10 times à 6-hour exposure of rats during a 14-day period) using MPMD as test material comparable local effects were observed in all treated groups thus yielding also a LOAEC of 9.2 mg/m³.

Furthermore, there is experimental evidence from a sub-chronic study with Hexamethylenediamine dihydrochloride (HDDC = salt of Hexamethylenediamine (HMD, CAS 124-09-4)). HMD is another C6-diamine but linear instead of cyclic as DCH or branched as MPMD. In this study with inhalation exposure of rats (6h/day, 5d/week for 13 weeks) also local respiratory effects were identified as critical. Under the test conditions, the NOAEC (HDDC) = 16 mg/m³/day for local respiratory damage (nasal respiratory epithelium degeneration), corresponding to a NOAEC (HMD) = 10 mg/m³/day. In another subchronic inhalation toxicity study with rats, the animals were repeatedly exposed to aqueous HMD aerosol for six hours per day, five days per week at mean analytical concentrations of 0, 12.8, 51 and 215 mg/m³. Under the test conditions, no systemic effects were observed related to the treatment with HMD. The significant local irritation of respiratory tract, inducing clinical signs, was observed at the two highest concentrations tested. The NOAEC in male and female rats exposed by whole-body inhalation was 12.8 mg HMD/m³.

Only one study is available using the submission substance. Thus, the LOAEC of the study will serve as starting point for the DNEL derivation. However, the experimental data on related amines serves as supporting evidence for verifying the local irritating nature of amines in general. Especially the sub-chronic studies with HMD and HMD-dihydrochloride verify that the effect is not crucially time dependent either - therefore no assessment factor was used for differences in duration of exposure.

 

DNEL derivation:

Basis LOAEC: 10 mg/m³ from 14 days toxicity study after aerosol/vapour exposure

Effects: dose dependent effects seen on the upper respiratory tract (e. g. nasal lesions) which were from minimal to moderate severity and were fully reversible within the 14-day recovery period

No correction of LOAEC was performed as local irritating effects are concentration dependent and are independent of the absorbed dose.

Assessment factors:

• Interspecies differences: no allometric scaling, 2.5 (remaining differences)


• Intraspecies differences: 10


• Differences in duration of exposure:    1 (no additional factor is required for exposure duration since the effect observed is not dependent on the time of exposure)


• Issues related to dose-response: 3 (starting point is LOAEC instead of NOAEC)


• Quality of whole database: 1 (no deficiencies)

--> Overall assessment factor: 75

DNEL = 10 mg/m³/75

DNEL = 133 µg/m³ = 0.13 mg/m³

 

General Population-DNEL short-term for inhalation route- local effects:

As an acute toxicity hazard has been identified (leading to C&L, i.e. STOT Single Exp. 3 (H335)) a DNEL for peak exposure has to be derived. Ideally sub-lethal toxicity should be the starting point rather than mortality. In our case from the acute inhalation toxicity study only information on mortality could be extracted as there were no detailed descriptions on pathological findings included. Therefore repeated-dose data from the sub-acute inhalation study with the submission substance is thought to better characterize the acute hazard originating from the toxicological profile of the substance.

Effects after repeated application of the submission substance by inhalation to rats were restricted to the respiratory tract. Therefore, an acute DNEL inhalation for local effects was established from the GENERAL POPULATION DNEL LONG-TERM FOR INHALATION ROUTE, LOCAL EFFECTS by using a multiplying factor of 2 considering that the observed adverse effects are mainly driven by the exposure concentration of the submission substance with respect to its corrosive properties.

--> DNEL: 133 µg/m³ *2 = 267 µg/m³ ≈ 0.27 mg/m³

 

Below, the DNEL derivation for local and systemic effects are compared to evaluate which of the effects leads to the more conservative assessment. As systemic effects were only observed after oral exposure route-to-route extrapolation has to be performed. The study which identified the lowest NOAEL was used.

(Please note: The higher NOAELs identified in the OCED 422 and 414 study would lead to comparable DNELs for systemic effects as calculated below for the descriptor of the 90-day study. This is due to shorter exposure durations and thus the higher time extrapolation factors that have to be applied.)

General population long-term DNEL inhalation	Local	Systemic
Step a: determination of dose-descriptor
Key study	HLR 555-93, no OECD Guideline	Labcorp 2022, OECD 408
Relevant dose descriptor	LOAEC = 10 mg/m³for local irritant effects of the upper respiratory tract in rats	NOAEL = 50 mg/kg bw/day (systemic effects on male rats)
Step b: correct starting point		*
Differences in metabolic rate per b.w. (allometric scaling)	- (local effects)	4 (rat)
Differences in absorption depending on route of exposure (route-route extrapolation, human/animal)	-       - (local effects)	-     2 (worst case assumption according to ECHA guidance R.8: 50% oral and 100% inhalation exposure)
Modification for exposure (experiment and human)	-       - (local irritant effects depending on concentration, only)	-      - (daily dose)
Modification for respiratory volume	-	X 70 kg bw / 20 m³ respirator volume per 24 h
Correct starting point = relevant dose descriptor / overall factor for uncertainties	10 mg/m³	22 mg/m³
Step c : assessment factors
Interspecies differences	2.5 (effects on respiratory tract)	2.5 (remaining differences
Intraspecies differences	10	10
Duration extrapolation (sub-acute/sub-chronic/chronic)	1 (no additional factor is required for exposure duration since the effect observed is not dependent on the time of exposure)	2 (subchronic to chronic)
Issues related to dose-response	3 (LOAEC)	1
Quality of whole database	1	1
Overall assessment factor	75	50
DNEL calculation	0.13 mg/m³	0.44 mg/m³

* Please note this is one of the ways shown in ECHA Guidance on information requirements and chemical safety assessment Chapter R.8, APPENDIX R. 8-2, Example R. 8-1 Workers (or Figure R. 8-3) for correction of the starting point. This is not the preferred way, but here differences from the local DNEL derivation can be pointed out. The preferred way (i.e. 50 mg/kg bw/day / 1.15 m³/kg bw * 50% / 100%) leads to the same numerical value.

Final conclusion:

The inhalation general population DNEL long-term calculated for local effects is 0.13 mg/m³ compared to 0.44 mg/m³ for systemic effects. The lower DNEL for local effects is considered to be protective also regarding systemic effects and taken forward for risk characterisation.

 

General population-DNEL long-term oral - systemic effects:

The DNEL long-term, oral exposure, systemic effects is derived from a toxicity study with oral exposure. The most sensitive NOAEL for this category was the NOAEL of 50 mg/kg bw/day identified in the Repeated Dose 90-day Oral Toxicity Study (OECD 408) with oral exposure to DCH. In the high and mid dose groups (i.e. 500 mg/kg bw/d and 150 mg/kg bw/d, respectively) adverse effects on reproductive organs were observed for male rats. Additionally observed adverse findings in the high dose groups comprised reduction of male overall body weight gain, aggregations of alveolar macrophages associated with interstitial mixed inflammatory cell infiltrates in the lungs and changes in the hemolymphoreticular system of both sexes. No mortality attributed to the test material treatment was observed during the study (highest dose tested 500 mg/kg bw/day).

DNEL derivation:

Basis NOAEL: 50 mg/kg bw/day from Repeated Dose 90-day Oral Toxicity Study (OECD 408; male rats)

As no specific values on oral absorption are available --> therefore default assumption for oral absorption: 100 %

 

Assessment factors:

• Interspecies differences:        4 (allometric scaling), 2.5 (remaining differences)


• Intraspecies differences:      10


• Differences in duration of exposure:            2 (sub-chronic to chronic)


• Issues related to dose-response:             1 (none)


• Quality of whole database:       1 (no deficiencies)

--> Overall assessment factor: 200

DNEL = 50 mg/kg bw/day / 200

DNEL = 0.25 mg/kg bw/day

 

General population-DNEL short-term oral - systemic effects:

An acute DNEL by oral route should be derived if an acute toxicity hazard has been identified AND if the exposure assessment has predicted high peaks (see Appendix R8.8 in Guidance on information requirements and chemical safety assessment Chapter R.8, version 2.1 of Nov 2012). Although classified as harmful if swallowed, no peak exposure is predicted for human exposed to DCH via the environment. Therefore, no DNEL acute for oral route has been derived.