1-Hexyl 4,5-diamino pyrazole hemisulfate

Endpoint summary

Description of key information

The acute oral toxicity of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was determined from a 28-day repeated dose finding study conducted using the dihydrochloride salt. The determined LD50, oral value of 218 mg/kg bw is considered conservative since none of the animals died at this dose and it was 10-fold lower than that of a structurally related chemical. It was also in accordance with the required test concentrations and possible LD50 estimations (between 50 and 300 mg/kg bw) for the OECD. Based on the calculated LD50 oral. value, 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE should be classified as Acute Tox Cat.3; H301: “toxic if swallowed”, according to the Globally Harmonized System of Classification and Labeling (GHS).

Based on the available acute oral toxicity and toxicokinetics data for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, the acute dermal, as well as acute inhalation, toxic potential for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE could be calculated.

The calculated inhalation toxicity value (LC50, inhal.) for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is 2.51 mg/L. When this concentration is combined with the results of in vitro eye irritation studies, it can be concluded that the substance would not have a local effect in the lungs. The calculated LC50, inhal. is consistent with the measured value (in in vivo studies) for an analogue of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, namely 1-hydroxyethyl-4,5-diamino pyrazole sulphate. Based on the calculated LC50 inhal. value, 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE should be classified as Acute Tox Cat.3; H331: “toxic if inhaled”, according to the Globally Harmonized System of Classification and Labeling (GHS).

As demonstrated by the toxicokinetics data, the bioavailability after application to the skin is lower than the oral bioavailability. The calculated acute dermal toxicity (LD50, dermal) of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is 1050 mg/kg bw. Therefore, it should be classified as Acute Tox Cat.4; H312: “harmful in contact with skin”, according to the Globally Harmonized System of Classification and Labeling (GHS).

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Justification for type of information:

The calculation of acute toxicity values for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is based on the current understanding and knowledge of the test substance. Toxicity data were obtained from publically available publications such as the opinion document from the Scientific Committee on Consumer Safety of the European Commission on 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, and study reports provided by Service Germany GmbH. If more (detailed) information becomes available or if updated guidance becomes available, the statement might be subject to review

Qualifier:

no guideline followed

Principles of method if other than guideline:

The calculation of acute toxicity values for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is based on the current understanding and knowledge of the test substance. Toxicity data were obtained from publically available publications such as the opinion document from the Scientific Committee on Consumer Safety of the European Commission on 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, and study reports provided by Service Germany GmbH. If more (detailed) information becomes available or if updated guidance becomes available, the statement might be subject to review

Key result

Sex:

not specified

Dose descriptor:

LD50

Effect level:

ca. 218 mg/kg bw

Oral LD₅₀value using data from repeated dose toxicity studies and evaluation of applicability of thein vivoMTD data to meet OECD requirements for acute oral toxicity

 

The acute oral toxicity of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwas not investigated.

However, no deaths were observed in the sub-chronic (13-week) oral toxicity study (Ref 2) or in the developmental toxicity study in rats (Ref 3) at dose levels up to 20 mg/kg bw/day. Likewise, in a 28-day repeated dose range finding study in rats (Ref 4), none of the doses up to 240 mg/kg bw /day caused any deaths. This 28-day dose range finding study for the 90-day study was not carried out as a GLP study and was conducted using the dihydrochloride salt.

 

Since no additionalin vivostudies are available, a conservative value for the oral acute toxicity (LD₅₀,oral) of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwas set at 218 mg/kg bw. This was calculated by applying a conversion factor of 0.91 to the LD₅₀value of 240 mg/kg based on the molar mass differences between the hydrochloride and hemisulfate salt of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE(Ref 1). This derived LD₅₀value is within the required test concentrations and possible LD₅₀estimations, namely between 50 and 300 mg/kg bw for the OECD.

 

 

Table 1: Comparison of study requirements from OECD guidelines for acute oral toxicity study(f = female, m = male).

Test type	Guideline (OECD)	Animal species	Doses (mg/kg bw)	animal number	observation period	determined LD50mg/kg bw
Acute oral toxicity	423 (Ref 5)	Rat	5, 50, 300, 2000 (Guideline recommendation)	3/dose (Total: 3 to 12)	1 to 14 days	Possible values: 5, 25, 50, 200, 300, 500, 2000, 2500, 5000
28-Day repeated dose (Ref 4)	407 (Ref 6)   Not GLP compliant	Rat	Determination of MTD (doses tested: 26, 80, 240)	(required: min. 3) 10 to 15/dose (m & f)	28 days	LD50: >240 (none of the animals died) MTD: >240

 

 

Result:

LD_{50 calc}oral 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE= 218 mg/kg bw

 

Conclusion: Based on the above, a conservative value for the LD₅₀of 218 mg/mg/kg bw determined from the 28-day repeated toxicity study was used for the calculations of the acute dermal and inhalation toxicity potential of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE. This LD₅₀, oralvalue is in line with the OECD criteria.

 

Data from anin vivoADME studies

 

The oral bioavailability of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEbased on the blood AUC was high (93%) compared to the AUC after i.v. administration. When calculated from the urine data from the mass balance groups, the oral bioavailability was also determined to be high and was 84% at 12 mg/kg bw (Table 2).

 

The average dermal absorption of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE,when calculated from the urine data from the mass balance groups, was low, and was 9% at 11 mg/kg bw (0.5 hours exposure) and 17% at 11.5 mg/kg bw (24 hours exposure).

 

After i.v. and oral administration, elimination, mainly via the urine, was fast, with 85% of the total amount being excreted within in the first 48 h. The elimination after dermal doses was relatively slow, with 62% and 50% of the absorbed radioactive dose recovered by 48 h after a 0.5 h and 24 h exposure, respectively.

 

 

 

Table 2:   Overview of the mass balance data from the ADME study with1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEin rats

Group No.	1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEDose Level / Concentration	Dosing route	Absorption (%)	Excretion via urine/feces (%) (relative to administered dose)
1	11.9 mg/kg bw	i.v.	100	69 / 12
2	12 mg/kg bw	oral	82	69 / 15
3	11 mg/kg bw; 0.186 mg/cm² (0.5 hours exposure)	dermal	9*	3 / 4
4	11.5 mg/kg bw; 0.208 mg/cm² (24 hours exposure)	dermal	17*	8 / 6

*: Percentage of the dose recovered from: excretion + exhaled air + cage-wash + carcass.

 

For appropriate comparability between the different application routes, the mass balance data were used in the calculations of inhalation and dermal acute toxicity according to the applicability to the endpoint to derive the most conservative extrapolation.

 

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

The acute oral toxicity of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was determined from a 28-day repeated dose finding study conducted using the dihydrochloride salt. The determined LD50, oral value of 218 mg/kg bw is considered conservative since none of the animals died at this dose and it was 10-fold lower than that of a structurally related chemical. It was also in accordance with the required test concentrations and possible LD50 estimations (between 50 and 300 mg/kg bw) for the OECD. Based on the calculated LD50 oral. value, 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE should be classified as Acute Tox Cat.3; H301: “toxic if swallowed”, according to the Globally Harmonized System of Classification and Labeling (GHS).

Executive summary:

1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is a diaminopyrazole and is an ingredient used in oxidative hair coloring products.

Based on the available in vivo repeated dose toxicity study of the dihydrochloride salt (Ref 4), together with a toxicokinetics study of orally and topically applied hemisulfate salt (ADME) (Ref 6), the acute oral toxicity of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE could be determined, as well as its acute dermal and acute inhalation toxic potential.

The pre-clinical toxicity studies were carried out with two forms of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE, namely the hemisulfate salt and the dihydrochloride salt. The free base component is considered responsible for the toxic potential of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE salts. Therefore, studies carried out with the hemisulfate and dihydrochloride salts are both relevant for the risk assessment of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE upon adjustment for molecular weight and content. Correspondingly, in all studies performed with the dihydrochloride salt, the concentrations used were converted to the concentration of the hemisulfate salt by applying a conversion factor of 0.91 adjusting for the differences in molecular weight and free base content (Ref 1).

The acute oral toxicity of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was not investigated.

However, no deaths were observed at doses up to 240 mg/kg bw /day in a 28-day repeated dose range finding study in rats using the dihydrochloride salt (Ref 3). This value was adjusted using the conversion factor of 0.91 to result in an oral LD50 value of 218 mg/kg for the hemisulfate salt. Since no additional in vivo studies are available, a conservative value for the oral acute toxicity (LD50, oral) of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was set at 218 mg/kg bw. This derived LD50 value is within the required test concentrations and possible LD50 estimations for the OECD. The LD50, calc, oral of 218 mg/kg bw was therefore used for the route extrapolation calculations.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

218 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Justification for type of information:

The calculation of acute toxicity values for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is based on the current understanding and knowledge of the test substance. Toxicity data were obtained from publically available publications such as the opinion document from the Scientific Committee on Consumer Safety of the European Commission on 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, and study reports provided by Service Germany GmbH. If more (detailed) information becomes available or if updated guidance becomes available, the statement might be subject to review

Qualifier:

no guideline followed

Principles of method if other than guideline:

The calculation of acute toxicity values for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is based on the current understanding and knowledge of the test substance. Toxicity data were obtained from publically available publications such as the opinion document from the Scientific Committee on Consumer Safety of the European Commission on 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, and study reports provided by Service Germany GmbH. If more (detailed) information becomes available or if updated guidance becomes available, the statement might be subject to review

Key result

Sex:

not specified

Dose descriptor:

LC50

Effect level:

ca. 2.51 mg/L air

Remarks on result:

other:

Remarks:

extrapolated and calculated

Data from anin vivoADME studies   The oral bioavailability of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEbased on the blood AUC was high (93%) compared to the AUC after i.v. administration. When calculated from the urine data from the mass balance groups, the oral bioavailability was also determined to be high and was 84% at 12 mg/kg bw (Table 2).   The average dermal absorption of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE,when calculated from the urine data from the mass balance groups, was low, and was 9% at 11 mg/kg bw (0.5 hours exposure) and 17% at 11.5 mg/kg bw (24 hours exposure).   After i.v. and oral administration, elimination, mainly via the urine, was fast, with 85% of the total amount being excreted within in the first 48 h. The elimination after dermal doses was relatively slow, with 62% and 50% of the absorbed radioactive dose recovered by 48 h after a 0.5 h and 24 h exposure, respectively.       Table 2:   Overview of the mass balance data from the ADME study with1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEin rats Group No. 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEDose Level / Concentration Dosing route Absorption (%) Excretion via urine/feces (%) (relative to administered dose) 1 11.9 mg/kg bw i.v. 100 69 / 12 2 12 mg/kg bw oral 82 69 / 15 3 11 mg/kg bw; 0.186 mg/cm² (0.5 hours exposure) dermal 9* 3 / 4 4 11.5 mg/kg bw; 0.208 mg/cm² (24 hours exposure) dermal 17* 8 / 6 *: Percentage of the dose recovered from: excretion + exhaled air + cage-wash + carcass.   For appropriate comparability between the different application routes, the mass balance data were used in the calculations of inhalation and dermal acute toxicity according to the applicability to the endpoint to derive the most conservative extrapolation.
Extrapolation from oral to inhalation acute toxicity of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE:   Values and assumptions used in the calculations: 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATELD₅₀oral= 218 mg/kg bw in the rat   Oral Bioavailability = 82% (at 12 mg/kg bw, using the data from the toxicokinetics study in Wistar rats (Ref 7).   Required max. exposure conc. to test material (OECD 403,(Ref 8)):                             5 mg/L  

• Assumed body weight of the rat:                                                                                 250 g

 

• Respiratory volume of the rat(Ref 9):                                                                           0.074 L/min

 

• Required duration (OECD 403,(Ref 8))                                                                       4 h

 

• Inhalation Bioavailability (assumed, worst case assumption):                                       100%

 

 

Calculations:

 

Maximum volume of exposure in 4 hours:

 

0.074 L/min x 60 min x 4 hours = 17.76 L                                                                   Equation 1

 

 

Determination of the correction factor oral vs. inhalation route:

 

Ratio of 82% oral : 100% inhalation = 0.82                                                                  Equation 2

 

 

 

Determination of the LC_{50 calc}inhal.:     

 
[(218 mg/kg bw x 0.250 kg bw )/ 17.76L]x 0.82 = 2.51 mg/L Equation 3

 

 

Result: LC_{50 calc}inhal.1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE   = 2.51 mg/L

Assessment of possible local effects of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE in the lung

 

Local irritation of the lung mucosal membranes can lead to death; therefore, the potential for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEto cause local lung mucous membrane irritation was evaluated by comparing theLC_{50 calc}inhal. for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwith thelocal irritating effect measured in thein vitroIsolated Chicken Eye (ICE) Test and the conditions of the acute inhalation toxicity maximal tested dose .

 

 

Calculations:

 

Comparison with eye irritation effects:

 

1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEas neat substance and at 1.5% (w/w) in aqueous solution is not irritating to eyes.1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEtested at 5% (w/w) was identified as mildly irritating to eyes. The SCCS concluded that1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEas neat substance and at 1.5% (w/w) in aqueous solution is not a strong eye irritant .

 

 

Conversion of LC_{50 calc}inhal. to % (w/w):

 

1 L air: 1.2041 kg/m³ = 1204.1 g/m³ = 1204100 mg/m³ = 1204100/1000 L = 1201 mg/L           Equation 4

1201 mg/L = 100 %

2.51 mg/L air = 0.21 % (w/w)                                                                                                 Equation 5

 

The concentration of 0.21% (w/w)1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEis 6.5-fold lower than the lowest concentration tested in the ICE test (1.5%) at which concentration no irritation was observed.

 

 

Result: The concentration of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATErepresents 0.21% in an aerosol. By comparing the LC_{50 calc}inhal. with the results of thein vitroICE test , it can be concluded that1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwould not havea local effect in thelungs.

Comparative data of similar functional and structural hair dye molecules

 

The calculated oral LD₅₀and inhalation LC₅₀values for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwere compared to those with a structurally similar molecule (Table 3). Four other structurally similar chemicals to1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwere identified (CAS numbers 173994-77-9, 163183-00-4, 889657-07-2 and 173994-78-0); however, corresponding measured oral, inhalation and dermal acute toxicity data were unavailable.

 

 

 

Table 3:   Overview of chemical structures as well as oral and acute inhalational toxicity data for a structurally-related molecule to1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE. For this chemical, the SCCS issued scientific opinion, which is included in regulatory requirements.

COLIPA Number	Chemical Structure	Chemical Name	CAS Number	Acute Toxicity
				Oral LD50	Dermal LD50	Inhalation LC50
Colipa No. A163		1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE	1361000-03-4	218 mg/kg bw	1050 mg/kg bw	2.51 mg/L,
Colipa No. A154		1-Hydroxyethyl-4,5-diamino pyrazole sulphate	155601-30-2	>2000 mg/kg bw (rat) (Ref 12)	Not available	> 5.24 mg/L,  (4 h, rat) (Ref 12)

 

Conclusion: The calculated oral LD₅₀for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was 10-fold lower than that of a structurally related chemical, indicating the conservative estimate of this value. Acute dermal toxicity data were not available for the analogue. The inhalation LC₅₀derived in this document for1‑HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwas in line with that measured for the structurally similar molecule, hence further reassuring the validity of the scientific information.

Summary:

The acute oral toxicity of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwas determined from a 28-day repeated dose finding study conducted using the dihydrochloride salt. The determined LD₅₀, oralvalue of 218 mg/kg bw is considered conservative since none of the animals died at this dose and it was 10-fold lower than that of a structurally related chemical. It was also in accordance with the required test concentrations and possible LD₅₀estimations (between 50 and 300 mg/kg bw) for the OECD. Based on the calculated L₅₀oral. value,1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEshould be classified as Acute Tox Cat.3; H301: “toxic if swallowed”, according to the Globally Harmonized System of Classification and Labeling (GHS).

 

Based on the available acute oral toxicity and toxicokinetics data for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, the acute dermal, as well as acute inhalation, toxic potential for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEcould be calculated.

 

The calculated inhalation toxicity value (LC₅₀,inhal.) for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEis 2.51 mg/L. When this concentration is combined with the results ofin vitroeye irritation studies, it can be concluded that the substance would not havea local effect in the lungs. The calculated LC₅₀,inhal. is consistent with the measured value (inin vivostudies) for an analogue of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, namely 1-hydroxyethyl-4,5-diamino pyrazole sulphate. Based on the calculated LC₅₀inhal. value,1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEshould be classified as Acute Tox Cat.3; H331: “toxic if inhaled”, according to the Globally Harmonized System of Classification and Labeling (GHS).

 

As demonstrated by the toxicokinetics data, the bioavailability after application to the skin is lower than the oral bioavailability. The calculated acute dermal toxicity (LD₅₀,dermal) of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEis 1050 mg/kg bw. Therefore, it should be classified as Acute Tox Cat.4; H312: “may be harmful in contact with skin”, according to the Globally Harmonized System of Classification and Labeling (GHS).

 

 

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

Based on the available acute oral toxicity and toxicokinetics data for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, the acute dermal, as well as acute inhalation, toxic potential for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE could be calculated.

The calculated inhalation toxicity value (LC50, inhal.) for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is 2.51 mg/L. When this concentration is combined with the results of in vitro eye irritation studies, it can be concluded that 2-METHOXY-METHYL-P-PHENYLENEDIAMINE would not have a local effect in the lungs. The calculated LC50, inhal. is consistent with the measured value (in in vivo studies) for an analogue of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, namely 1-hydroxyethyl-4,5-diamino pyrazole sulphate. Based on the calculated LC50 inhal. value, 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE should be classified as Acute Tox Cat.3; H331: “toxic if inhaled”, according to the Globally Harmonized System of Classification and Labeling (GHS).

Executive summary:

The acute dermal and inhalational toxicity of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was determined using kinetics-based data derived from an ADME study in rats . The calculated LC50 for inhalation (LC50 calc inhal.) was 2.51 mg/L. When this concentration is combined with the results of in vitro eye irritation studies (ICE) it can be concluded that 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE would not have a local effect in the lungs.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

2.51 mg/m³

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Justification for type of information:

The calculation of acute toxicity values for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is based on the current understanding and knowledge of the test substance. Toxicity data were obtained from publically available publications such as the opinion document from the Scientific Committee on Consumer Safety of the European Commission on 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, and study reports provided by Service Germany GmbH. If more (detailed) information becomes available or if updated guidance becomes available, the statement might be subject to review

Qualifier:

no guideline followed

Principles of method if other than guideline:

The calculation of acute toxicity values for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is based on the current understanding and knowledge of the test substance. Toxicity data were obtained from publically available publications such as the opinion document from the Scientific Committee on Consumer Safety of the European Commission on 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, and study reports provided by Service Germany GmbH. If more (detailed) information becomes available or if updated guidance becomes available, the statement might be subject to review

Key result

Sex:

not specified

Dose descriptor:

LD50

Effect level:

ca. 1 050 mg/kg bw

Remarks on result:

other:

Remarks:

extrapolated and calculated

Data from anin vivoADME studies

 

The oral bioavailability of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEbased on the blood AUC was high (93%) compared to the AUC after i.v. administration. When calculated from the urine data from the mass balance groups, the oral bioavailability was also determined to be high and was 84% at 12 mg/kg bw (Table 2).

 

The average dermal absorption of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE,when calculated from the urine data from the mass balance groups, was low, and was 9% at 11 mg/kg bw (0.5 hours exposure) and 17% at 11.5 mg/kg bw (24 hours exposure).

 

After i.v. and oral administration, elimination, mainly via the urine, was fast, with 85% of the total amount being excreted within in the first 48 h. The elimination after dermal doses was relatively slow, with 62% and 50% of the absorbed radioactive dose recovered by 48 h after a 0.5 h and 24 h exposure, respectively.

 

 

 

Table 2:   Overview of the mass balance data from the ADME study with1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEin rats

Group No.	1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEDose Level / Concentration	Dosing route	Absorption (%)	Excretion via urine/feces (%) (relative to administered dose)
1	11.9 mg/kg bw	i.v.	100	69 / 12
2	12 mg/kg bw	oral	82	69 / 15
3	11 mg/kg bw; 0.186 mg/cm² (0.5 hours exposure)	dermal	9*	3 / 4
4	11.5 mg/kg bw; 0.208 mg/cm² (24 hours exposure)	dermal	17*	8 / 6

*: Percentage of the dose recovered from: excretion + exhaled air + cage-wash + carcass.

 

For appropriate comparability between the different application routes, the mass balance data were used in the calculations of inhalation and dermal acute toxicity according to the applicability to the endpoint to derive the most conservative extrapolation

Extrapolation from oral to dermal acute toxicity of1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE:

Values and assumptions used in the calculations:

 

• 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATELD₅₀oral= 218 mg/kg bw in the rat

 

• Oral Bioavailability = 82% (at 12 mg/kg bw, using the data from the toxicokinetics study in Wistar rats).

 

• Dermal bioavailability = 17% (24 h exposure). This value was selected (assuming higher toxicity resulting from a higher bioavailability) because incorporation of this value into Equation 6 results in a lowerLD_{50 calc}dermalvalue (with an assumed higher toxicity). In addition, dermal absorption is dose-dependent, such that higher does leads to lower absorption; therefore, the high LD₅₀dose would be expected to have lower absorption than assumed for this calculation.

 

 

Calculation:

 

Determination of the correction factor oral vs. dermal route:

 

82% oral vs. 17% dermal = 9.11 (82 / 17 = 4.82)                                                         Equation 6

 

 

Determination of the LD_{50 calc}dermal:

 

218 mg/kg bw x 4.82 = 1050 mg/kg bw                                                                       Equation 7

 

 

Result: LD_{50 calc}dermal1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE = 1050 mg/L

Comparative data of similar functional and structural hair dye molecules

 

The calculated oral LD₅₀and inhalation LC₅₀values for1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwere compared to those with a structurally similar molecule (Table 3). Four other structurally similar chemicals to1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATEwere identified (CAS numbers 173994-77-9, 163183-00-4, 889657-07-2 and 173994-78-0); however, corresponding measured oral, inhalation and dermal acute toxicity data were unavailable.

 

 

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

As demonstrated by the toxicokinetics data, the bioavailability after application to the skin is lower than the oral bioavailability. The calculated acute dermal toxicity (LD50, dermal) of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is 1050 mg/kg bw. Therefore, it should be classified as Acute Tox Cat.4; H312: “may be harmful in contact with skin”, according to the Globally Harmonized System of Classification and Labeling (GHS).

Executive summary:

The acute oral toxicity of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was not investigated.

However, no deaths were observed at doses up to 240 mg/kg bw /day in a 28-day repeated dose range finding study in rats using the dihydrochloride salt. This value was adjusted using the conversion factor of 0.91 to result in an oral LD50 value of 218 mg/kg for the hemisulfate salt. Since no additional in vivo studies are available, a conservative value for the oral acute toxicity (LD50, oral) of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was set at 218 mg/kg bw. This derived LD50 value is within the required test concentrations and possible LD50 estimations for the OECD. The LD50, calc, oral of 218 mg/kg bw was therefore used for the route extrapolation calculations.

For the dermal end point, the data derived from the ADME study (with respect to the duration of test item and animal number was in line with the OECD guideline 402 for acute dermal toxicity. The approach to determine dermal toxicity by using oral data is accepted by the German and EU regulatory bodies and is based on the current state-of-the-art science. For the determination of the acute dermal toxicity, the bioavailability after topical application was used, which is lower than the oral bioavailability. The calculated LD50 for dermal toxicity (LD50 calc dermal) was 1050 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 050 mg/kg bw

Additional information

The determination of the LD50 from the 28-day repeated dose range finding study in rats was in line with the OECD guideline 423 for the determination of acute oral toxicity (Ref 5). This approach is accepted by the German and EU regulatory agencies and is based on current state-of-the-art science.

Since the Weight of Evidence Approach (WoE) used was considered as sufficiently robust to determine the acute dermal and inhalation toxic potential of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, the performance of an animal test for hazard identification purposes was considered to be not justified.

For the dermal end point, data derived from the ADME study (duration of test item and animal number) were in line with the OECD guideline 402 for acute dermal toxicity. The approach to determine dermal toxicity using oral data is accepted by the German (Ref 13) and EU regulatory bodies and is based on the current state-of-the-art science.

In addition, the conduct of acute in vivo toxicity studies on 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE as an ingredient used in cosmetic products would not comply with the EU regulations regarding animal testing. Furthermore, applying WoE complies with the REACH regulation to avoid animal testing. The validity of the WoE/extrapolation approach used in order to estimate the acute toxicity potential of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE by the dermal and inhalation routes was confirmed by the comparison of the extrapolated values for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE with experimental values obtained on chemical analogues.

Justification for classification or non-classification

The acute oral toxicity of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE was determined from a 28-day repeated dose finding study conducted using the dihydrochloride salt. The determined LD50, oral value of 218 mg/kg bw is considered conservative since none of the animals died at this dose and it was 10-fold lower than that of a structurally related chemical. It was also in accordance with the required test concentrations and possible LD50 estimations (between 50 and 300 mg/kg bw) for the OECD. Based on the calculated LD50 oral. value, 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE should be classified as Acute Tox Cat.3; H301: “toxic if swallowed”, according to the Globally Harmonized System of Classification and Labeling (GHS).

Based on the available acute oral toxicity and toxicokinetics data for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, the acute dermal, as well as acute inhalation, toxic potential for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE could be calculated.

The calculated inhalation toxicity value (LC50, inhal.) for 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is 2.51 mg/L. When this concentration is combined with the results of in vitro eye irritation studies, it can be concluded that the substance would not have a local effect in the lungs. The calculated LC50, inhal. is consistent with the measured value (in in vivo studies) for an analogue of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE, namely 1-hydroxyethyl-4,5-diamino pyrazole sulphate. Based on the calculated LC50 inhal. value, 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE should be classified as Acute Tox Cat.3; H331: “toxic if inhaled”, according to the Globally Harmonized System of Classification and Labeling (GHS).

As demonstrated by the toxicokinetics data, the bioavailability after application to the skin is lower than the oral bioavailability. The calculated acute dermal toxicity (LD50, dermal) of 1-HEXYL-1H-PYRAZOLE-4,5-DIAMINE HEMISULFATE is 1050 mg/kg bw. Therefore, it should be classified as Acute Tox Cat.4; H312: “harmful in contact with skin”, according to the Globally Harmonized System of Classification and Labeling (GHS).