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Acute Toxicity: dermal

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Endpoint:
acute toxicity: dermal
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2001-08-22 - 2001-10-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-Guideline Study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
see target record
Cross-reference
Reason / purpose:
read-across source
Remarks:
link to target
Reference
Endpoint:
acute toxicity: dermal
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Study period:
2001-08-22 - 2001-10-05
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Klimisch 1 source record, but performed on read-across substance
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH

According to ECHA’s guidance document on information requirements and chemical safety assessment Chapter R.6 „QSARs and grouping of chemicals”, there are two techniques for grouping chemicals known when reading across to cover data gaps, i.e., category approach and analogue approach [ECHA, 2008].
A chemical category is a group of chemicals whose physico-chemical and human health and/or environmental toxicological properties and/or environmental fate properties are likely to be similar or follow a regular pattern as a result of structural similarity (or other similarity characteristic). The term analogue approach is used when the grouping is based on a very limited number of chemicals, where trends in properties are not apparent. Categories of chemicals are selected based on the hypothesis that the properties of a series of chemicals with common structural features will show coherent trends in their physico-chemical properties, and more importantly, in their toxicological (human health / ecotoxicity) effects or environmental fate properties [ECHA, 2008].
As set out in the guidance document, a chemical category is a group of chemicals whose physico-chemical and human health and/or environmental toxicological properties and/or environmental fate properties are likely to be similar or follow a regular pattern as a result of structural similarity. The similarities may be based on the following:
- common functional group(s) (e.g. aldehyde, epoxide, ester, specific metal ion);
- common constituents or chemical classes, e.g., similar carbon range numbers;
- an incremental and constant change across the category (e.g. a chain-length category), often observed in physico-chemical properties, e.g. boiling point range;
- the likelihood of common precursors and/or breakdown products, via physical or biological processes, which result in structurally similar chemicals (e.g. the metabolic pathway approach of examining related chemicals such as acid/ester/salt) [ECHA, 2008].

It is aimed to combine similarity patterns in order to cover data gaps for PPSOH. One rational for the analogue approach is the high structural similarity between the source and the target substance. 3-pyridinium-1-ylpropane-1-sulfonate (PPS) (source) and 1-(2-hydroxy-3-sulphonatopropyl)pyridinium, inner salt (PPSOH) (target) are structurally identical except an additional hydroxyl group on position 2 of the propyl moiety of the target substance. Despite the fact that a hydroxyl group may alter the toxicological or toxicokinetic behaviour of a substance, this effect is considered minor as there are three common groups in the molecules which are considered more relevant for their toxicological behaviour, i.e. the sulfo-group, the propyl moiety and the pyridine. Due to the similarities in structure, similar physico-chemical properties of the substances are to be expected, which would result in a similar toxicokinetic behaviour and most likely also in very similar toxicodynamic and toxicological behaviour. Second, the target substance is not only a metabolite of the source chemical, resulting from CYP450 metabolization (ToxTree estimation, Ideaconsult Ltd (2004-2013). Estimation of Toxic Hazard – A decision Tree approach, version 2.6.6, http://toxtree.sourceforge.net/), but they also share common metabolites, as shown from additional modelling of the source chemical metabolites (see respective table in the attachment).
Further, both substances show similar (eco-)toxicological properties in the endpoints for which data for both substances is available, which is considered proof of the suitability of the analogue approach, i.e. cross-reading from PPS to PPSOH.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

Source Chemical: 3-pyridinium-1-ylpropane-1-sulfonate / Pyridinium, 1-(3-sulfopropyl)-, hydroxide, inner salt / CAS 15471-17-7 / EC 239-491-3 (PPS), SMILES [O-]S(=O)(=O)CCC[n+]1ccccc1, MW 201.2428, C8H11NO3S

Target Chemical: Pyridinium, 1-(2-hydroxy-3sulfopropyl)-, hydroxide, inner salt / 2-hydroxy-3-pyridinium-1-ylpropane-1-sulfonate / CAS 3918-73-8 / EC 223-485-2 (PPSOH) SMILES OC(C[n+]1ccccc1)CS(=O)(=O)[O-], MW 217.2422, C8H11NO4S

Both substances do not contain impurities to an extent which is expected to alter the outcome of the experimental results or read-across approach.

3. ANALOGUE APPROACH JUSTIFICATION
Comparing the actually available information on the substances with regard to their physico-chemical properties, the minor influence of the additional hydroxyl group of the target chemical becomes obvious. All relevant information on similar metabolites can be retrieved from the respective table, in brief, the target substance is not only a metabolite of the source chemical, resulting from CYP450 metabolization, but they also share common metabolites, as shown from additional modelling of the source chemical metabolites. Considering the non-metabolized source and target chemicals only, the molecular weight only differs in the weight of a hydroxyl group and is hence in the same range, i.e. 201.24 g/mol and 217.24 g/mol, indicating per se the potential for absorption.
Both substances are solids which melt under decomposition at rather high temperatures, i.e. ≥ 245°C and have hence a negligible vapour pressure. Both compounds are very soluble in water, and their logPow is in a negative range.

In general, absorption of a chemical is possible, if the substance crosses biological membranes. In case where no transport mechanisms are involved, this process requires a substance to be soluble, both in lipid and in water, and is also dependent on its molecular weight (substances with molecular weights below 500 are favourable for absorption). Relevant for the endpoint acute toxicity dermal and skin sensitisation is the absorption resp. retention in the skin. In order to cross the skin, a compound must first penetrate into the stratum corneum and may subsequently reach the epidermis, the dermis and the vascular network. The stratum corneum provides its greatest barrier function against hydrophilic compounds, whereas the epidermis is most resistant to penetration by highly lipophilic compounds. Substances with a molecular weight below 100 are favourable for penetration through the skin and substances above 500 are normally not able to penetrate. The substance must be sufficiently soluble in water to partition from the stratum corneum into the epidermis. Therefore if the water solubility is below 1 mg/L, dermal uptake is likely to be low. Additionally logPow values between 1 and 4 favour dermal absorption. In the case of both the target and source chemical, due to their high water solubility and very low logPow, their absorption is very likely to be hindered in the stratum corneum. Nevertheless, once reaching the epidermis, i.a. due to their common small size, their absorption is favoured.
Besides the common physico-chemical and toxicokinetic properties, they exhibit a similar toxicological behaviour. Both substances are relatively non-toxic, with oral LD50 values >5000 mg/kg bw, and are non-irritating the skin and eyes.
Hence, due to the above-mentioned similarities of the source and target chemical, with regard to their structure, functional groups, toxicokinetic and toxicological behaviour, it can be reasonably concluded that a similar behaviour of the target chemical regarding its acute dermal toxicity and skin-sensitizing properties compared to the source chemical can be expected.
As indicated by studies on gene mutations in bacteria (both substances), chromosome aberrations in mammalian cells (PPS) and gene mutations in mammalian cells (PPSOH), both substances are not genotoxic. It can hence be reasonable concluded that a positive result in a chromosome mutation test on PPSOH can be excluded and read-across is justified, an underestimation of the actual hazard for genotoxic insults is unlikely. Further, as both substances are not acutely toxic, i.e. oral LD50 values are >5000 mg/kg, due to their physico-chemical properties a relevant accumulation in the body can be neglected, and no systemic or reprotoxic effects at all were noted in the OECD 422 study on PPS at the limit dose of 1000 mg/kg, the target chemical PPSOH does not need to be regarded as harmful upon repeated exposure or reproductive toxicant, too.

Besides the common physico-chemical and toxicokinetic properties, they exhibit a similar ecotoxicological behaviour. Both substances are relatively non-toxic towards aquatic invertebrates, both 48h EC50 values and even NOECs were above the limit value for classification, the EC50(48h) was even shown to be > 1000 mg/l for PPSOH. PPS showed results of LC50 (96h) > 1000 mg/L and NOEC (96h) > 1000 mg/L in the trout in an acute fish toxicity study acc. OECD 203. The EC50(72h) in algae in a study acc. OECD 201 is also above 100 mg/l, allowing in summary the conclusion that acute toxicity testing in fish would also not indicate any hazardous properties of PPSOH, so the assumption of a similar ecotoxicity profile and so read-across from PPS is also justified here.
In consequence, a similar behaviour can be expected in microorganisms. PPS is non-toxic to microorganisms, in a OECD 209 no toxicity was observed at a concentration of 1000 mg/l, so the following values were obtained for activated sludge: EC50(3h) > 1000 mg/L, NOEC(3h) = 1000 mg/L. This allows the conclusion that the substance is relatively non-toxic towards microorganisms.

Hence, due to the above-mentioned similarities of the source and target chemical, with regard to their structure, functional groups, common metabolites, toxicokinetic and ecotoxicological behaviour, it can be reasonably concluded that a similar behaviour of the target chemical regarding its ecotoxicological and toxicological properties compared to the source chemical can be expected. In summary, the target chemical PPSOH needs to be regarded as relatively non-toxic.


4. DATA MATRIX
The following table shows the available data relevant to justify the read-across from the source to the target chemical for several endpoints in order to omit testing for animal welfare:

Endpoint Source: PPS Target: PPSOH
Molecular weight 201.24 g/mol 217.24 g/mol
Physical state solid solid
Partition coefficient logPow < -2.78 at 21.5°C logPow < -2
Water solubility 240.5 g/L at 25°C (EpiSuite estimation) 1280 g/l at 23°C
Biodegradation 86 % degradation after 28 days Not readily biodegradable: no degradation observed (DOC) (OECD 301E)
readily biodegradable
Hydrolysis Not expected to undergo hydrolysis Hydrolysis can be excluded
Short-term toxicity to fish LC50 (96h) > 1000 mg/L, n/a
NOEC (96h) > 1000 mg/L (trout, OECD 203)
Short-term toxicity to aquatic invertebrates 24&48h NOEC ≥ 100 mg/L EC50(48h) > 1000 mg/l
24&48h EC50 > 100 mg/L (OECD 202) NOEC(48h) = 1000 mg/l (OECD 202)
Short-term toxicity to aquatic algae n/a EC50(72h) > 100 mg/l (OECD 201)
Toxicity to microorganisms EC50(3h) > 1000 mg/L, n/a
NOEC(3h) = 1000 mg/L (activated sludge, OECD 209)
MIC = 0.12 g/mL (Pseudomonas putida)
Acute toxicity oral LD50 > 5000 mg/kg (rat, OECD 401) LD50 > 5000 mg/kg (rat, OECD 423))
Acute toxicity dermal LD50 > 2000 mg/kg (rat, OECD 402) n/a
Skin irritation Not irritating (in vivo, rabbit) not corrosive (OECD 431, EpiDerm)
Eye irritation Not irritating (in vivo, rabbit) moderately irritant (HET-CAM, GLP)
Skin sensitization Not sensitizing (GPMT, OECD 406) n/a
Gene mutation in bacteria Negative ± S9 (OECD 471) negative ± S9 (OECD 471)
Chromosome aberration in mammalian cells Negative ± S9 (OECD 487) n/a
Gene mutation in mammalian cells n/a negative ± S9 (OECD 490)
Repeated dose toxicity NOAEL ≥ 1000 mg/kg (rat, OECD 422) n/a
Toxicity to reproduction NOAEL ≥ 1000 mg/kg (rat, OECD 422) n/a
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 402 (Acute Dermal Toxicity)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.3 (Acute Toxicity (Dermal))
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test type:
standard acute method
Limit test:
yes
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS: Sprague-Dawley CD (Crl: CD® (SD) IGS BR) strain rats
- On receipt the animals were randomly allocated to cages. The females were nulliparous and non-pregnant.
- Source: Charles River (UK) Ltd, Margate, Kent, UK.
- Animal selection: at random and given a unique number within the study by indelible ink-marking on the tail and a number written on a cage card.
- Age at study initiation: approximately eight weeks
- Weight at study initiation: at least 200 g
- Housing: housed in suspended polypropylene cages furnished with wood flakes, individually during the 24-hour exposure period and in groups of five, by sex, for the remainder of the study
- Diet (e.g. ad libitum): ad libitum (Rat and Mouse SQC Expanded Diet No. 1, Special Diets Services Limited, Witham, Essex, UK)
- Water (e.g. ad libitum): ad libitum drinking water
The diet, drinking water and bedding were routinely analysed and were considered not to contain any contaminants that could reasonably be expected to affect the purpose or integrity of the study.
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25°C (Any occasional deviations from these targets were considered not to have affected purpose or integrity of the study)
- Humidity (%): 30 to 70% (Any occasional deviations from these targets were considered not to have affected the purpose or integrity of the study)
- Air changes (per hr): at least fifteen per hours
- Photoperiod (hrs dark / hrs light): twelve hours continuous light (06:00 to 18:00) and twelve hours darkness

The animals were provided with environmental enrichment items: wooden chew blocks (B&K Universal Ltd, Hull, UK) and cardboard fun tunnels (Datesand Ltd, Cheshire, UK) or suitable alternatives. These items were considered not to contain any contaminant of a level that might have affected the purpose or integrity of the study.
Type of coverage:
semiocclusive
Vehicle:
other: distilled water
Details on dermal exposure:
TEST SITE
- Preparation: on the day before treatment the back and flanks of each animal were clipped free of hair.
- Area of exposure: approximately 10% of the total body surface area
- Type of wrap if used: A piece of surgical gauze was placed over the treatment area and semi-occluded with a piece of self-adhesive bandage.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): after the 24-hour contact period the bandage was carefully removed and the treated skin and surrounding hair wiped with cotton wool moistened with distilled water to remove any residual test material.

- Other: the absorption of the test material was not determined.
Duration of exposure:
24 hours
Doses:
2000 mg/kg bw
No. of animals per sex per dose:
5
Control animals:
not specified
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: observed for deaths or overt signs of toxicity 0.5, 1, 2 and 4 hours after dosing and subsequently once daily for fourteen days, Individual bodyweights were recorded prior to application of the test material on Day 0 and on Days 7 and 14.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight

All animals were subjected to gross necropsy.
Statistics:
Using the mortality data obtained, an estimate of the acute dermal median lethal dose (LD50) of the test material was made.
Sex:
male/female
Dose descriptor:
LD50
Effect level:
> 2 000 mg/kg bw
Based on:
test mat.
Remarks on result:
not determinable due to absence of adverse toxic effects
Sex:
male/female
Dose descriptor:
LD0
Effect level:
>= 2 000 mg/kg bw
Based on:
test mat.
Remarks on result:
not determinable due to absence of adverse toxic effects
Mortality:
No mortality occurred.
Clinical signs:
No signs of systemic toxicity occurred.
No signs of dermal irritation occurred.
Body weight:
One female animal showed a slight loss in bodyweight during the second week of the study. All other animals showed expected gains in bodyweight during the study.
Gross pathology:
No abnormalities were noted at necropsy.
Other findings:
No other findings were reported.
Interpretation of results:
GHS criteria not met
Remarks:
Criteria used for interpretation of results: EU-GHS
Conclusions:
The study was performed according to the OECD TG 402 without deviations and therefore considered to be of the highest quality (reliability Klimisch 1).The validity criteria of the test system was fulfilled. The test material did not induce any signs of acute dermal toxicity. The test material was considered to be not toxic via the dermal exposure route under the conditions of the test.
Executive summary:

The acute dermal toxicity of the test material was investigated in rats. The test was conducted according to OECD TG 402 and EU Method B. 3. 2000 mg/kg bw of the test substance was applied semiocclusive to the shaved skin of rats. After 24 h the animals were unwrapped and observations were made for a period of 14 days. No mortalities, signs of systemic toxicity, signs of dermal irritation, treatment-related body weight changes or pathological abnormalities were reported. The acute dermal median lethal dose (LD50) of the test material, in the Sprague-Dawley CD strain rat was found to be greater than 2000 mg/kg bodyweight.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 402 (Acute Dermal Toxicity)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.3 (Acute Toxicity (Dermal))
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test type:
standard acute method
Limit test:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): PPS SOLID
- Substance type: organic salt
- Physical state: white solid
- Lot/batch No.: 0300007/131
- Storage condition of test material: room temperature in the dark

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS: Sprague-Dawley CD (Crl: CD® (SD) IGS BR) strain rats
- On receipt the animals were randomly allocated to cages. The females were nulliparous and non-pregnant.
- Source: Charles River (UK) Ltd, Margate, Kent, UK.
- Animal selection: at random and given a unique number within the study by indelible ink-marking on the tail and a number written on a cage card.
- Age at study initiation: approximately eight weeks
- Weight at study initiation: at least 200 g
- Housing: housed in suspended polypropylene cages furnished with wood flakes, individually during the 24-hour exposure period and in groups of five, by sex, for the remainder of the study
- Diet (e.g. ad libitum): ad libitum (Rat and Mouse SQC Expanded Diet No. 1, Special Diets Services Limited, Witham, Essex, UK)
- Water (e.g. ad libitum): ad libitum drinking water
The diet, drinking water and bedding were routinely analysed and were considered not to contain any contaminants that could reasonably be expected to affect the purpose or integrity of the study.
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25°C (Any occasional deviations from these targets were considered not to have affected purpose or integrity of the study)
- Humidity (%): 30 to 70% (Any occasional deviations from these targets were considered not to have affected the purpose or integrity of the study)
- Air changes (per hr): at least fifteen per hours
- Photoperiod (hrs dark / hrs light): twelve hours continuous light (06:00 to 18:00) and twelve hours darkness

The animals were provided with environmental enrichment items: wooden chew blocks (B&K Universal Ltd, Hull, UK) and cardboard fun tunnels (Datesand Ltd, Cheshire, UK) or suitable alternatives. These items were considered not to contain any contaminant of a level that might have affected the purpose or integrity of the study.

Administration / exposure

Type of coverage:
semiocclusive
Vehicle:
other: distilled water
Details on dermal exposure:
TEST SITE
- Preparation: on the day before treatment the back and flanks of each animal were clipped free of hair.
- Area of exposure: approximately 10% of the total body surface area
- Type of wrap if used: A piece of surgical gauze was placed over the treatment area and semi-occluded with a piece of self-adhesive bandage.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): after the 24-hour contact period the bandage was carefully removed and the treated skin and surrounding hair wiped with cotton wool moistened with distilled water to remove any residual test material.

- Other: the absorption of the test material was not determined.
Duration of exposure:
24 hours
Doses:
2000 mg/kg bw
No. of animals per sex per dose:
5
Control animals:
not specified
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: observed for deaths or overt signs of toxicity 0.5, 1, 2 and 4 hours after dosing and subsequently once daily for fourteen days, Individual bodyweights were recorded prior to application of the test material on Day 0 and on Days 7 and 14.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight

All animals were subjected to gross necropsy.
Statistics:
Using the mortality data obtained, an estimate of the acute dermal median lethal dose (LD50) of the test material was made.

Results and discussion

Effect levelsopen allclose all
Sex:
male/female
Dose descriptor:
LD50
Effect level:
> 2 000 mg/kg bw
Based on:
test mat.
Remarks on result:
not determinable due to absence of adverse toxic effects
Sex:
male/female
Dose descriptor:
LD0
Effect level:
>= 2 000 mg/kg bw
Based on:
test mat.
Remarks on result:
not determinable due to absence of adverse toxic effects
Mortality:
No mortality occurred.
Clinical signs:
No signs of systemic toxicity occurred.
No signs of dermal irritation occurred.
Body weight:
One female animal showed a slight loss in bodyweight during the second week of the study. All other animals showed expected gains in bodyweight during the study.
Gross pathology:
No abnormalities were noted at necropsy.
Other findings:
No other findings were reported.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Remarks:
Criteria used for interpretation of results: EU-GHS
Conclusions:
The study was performed according to the OECD TG 402 without deviations and therefore considered to be of the highest quality (reliability Klimisch 1).The validity criteria of the test system was fulfilled. The test material did not induce any signs of acute dermal toxicity. The test material was considered to be not toxic via the dermal exposure route under the conditions of the test.
Executive summary:

The acute dermal toxicity of the test material was investigated in rats. The test was conducted according to OECD TG 402 and EU Method B. 3. 2000 mg/kg bw of the test substance was applied semiocclusive to the shaved skin of rats. After 24 h the animals were unwrapped and observations were made for a period of 14 days. No mortalities, signs of systemic toxicity, signs of dermal irritation, treatment-related body weight changes or pathological abnormalities were reported. The acute dermal median lethal dose (LD50) of the test material, in the Sprague-Dawley CD strain rat was found to be greater than 2000 mg/kg bodyweight.