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Description of key information

A well-conducted GLP OECD 422 study indicated no adverse effects up to the maximum dose of 1000 mg/kg/day which was established as the NOAEL.  

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
short-term repeated dose toxicity: oral
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
19 September 2012 to 07 December 2012 (end of in-life phase)
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP guideline study without significant deficiencies. Alkylated Naphthalene, EC Number 700-826-8 is a close structural analog of alkyl naphthalene. The substances have similar chemical and physical properites and the repeat dose toxicity testing for Alkylated Naphthalene, EC Number 700-826-8 can be used as read-across to alkyl naphthalene.
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
Environmental controls for the animal room were set to maintain 18 to 24 °C, a relative humidity of 40 to 70%, approximately 15 room air changes/hour, and a 12-hour light/12-hour dark cycle. Any variations to these conditions were maintained in the raw data and had no effect on the outcome of the study.

Rat: Crl:WI(Han) (outbred, SPF-Quality). Nulliparous and non-pregnant females and untreated animals were used at initiation of the study.

Source F0: Charles River Deutschland, Sulzfeld, Germany.

Age at start F0-treatment: Approximately 11 weeks.

Number of F0-animals: 40 females and 40 males.

Acclimatization F0: At least 5 days prior to start of treatment.

Health inspection F0: Upon receipt of the animals.

Randomization F0 Prior to commencement of treatment, by computer-generated random algorithm according to body weight, with all animals within ± 20% of the sex mean.
Route of administration:
oral: gavage
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Oral gavage, using a plastic feeding tube. Formulations were placed on a magnetic stirrer during dosing.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analytical testing of doses showed they were comparable to nominal target doses.
Duration of treatment / exposure:
Males were exposed for 29 days, i.e. 2 weeks prior to mating, during mating, and up to the day prior to scheduled necropsy. Females were exposed for 40-54 days, i.e. during 2 weeks prior to mating, during mating, during post-coitum, and during at least 4 days of lactation (up to the day prior to scheduled necropsy). Female nos. 66 (Group 4) and 75 (Group 4) were not dosed during littering.
Frequency of treatment:
once daily
Remarks:
Doses / Concentrations:
0 mg/kg bw/d
Basis:
actual ingested
Remarks:
Doses / Concentrations:
100 mg/kg bw/d
Basis:
actual ingested
Remarks:
Doses / Concentrations:
300 mg/kg bw/d
Basis:
actual ingested
Remarks:
Doses / Concentrations:
1000 mg/kg bw/d
Basis:
actual ingested
No. of animals per sex per dose:
10
Control animals:
yes, concurrent no treatment
Details on study design:
The purpose of this study was to evaluate the potential toxic effects of the test substance when administered to rats for a minimum of 28 days and to evaluate the potential of the test substance to affect male and female reproductive performance such as gonadal function, mating behaviour, conception, parturition and early postnatal development.
Parental, reproduction (up to and including implantation) and developmental (from implantation onwards) No Observed Adverse Effect Levels (NOAELs) were evaluated.
Positive control:
No
Observations and examinations performed and frequency:
The following observations and examinations were evaluated: mortality / viability, clinical signs (daily), functional observations and locomotor activity (end of treatment), body weight and food consumption (at least at weekly intervals), clinical pathology (end of treatment), macroscopy at termination, organ weights and histopathology on a selection of tissues, and reproduction/developmental parameters, consisting of mating, fertility and conception indices, precoital time, number of corpora lutea and implantation sites, gestation index and duration, parturition, maternal care, sex ratio and early postnatal pup development (mortality, clinical signs, body weights and macroscopy).
Sacrifice and pathology:
All males and the selected 5 females/group were deprived of food overnight (with a maximum of 24 hours) prior to planned necropsy, but water was provided. Non-selected females were not deprived of food. Animals were deeply anaesthetized using isoflurane (Abbott B.V., Hoofddorp, The Netherlands) and subsequently exsanguinated.
Statistics:
The following statistical methods were used to analyze the data:

If the variables could be assumed to follow a normal distribution, the Dunnett-test (many-to-one t-test) based on a pooled variance estimate was applied for the comparison of the treated groups and the control groups for each sex.
The Steel-test (many-to-one rank test) was applied if the data could not be assumed to follow a normal distribution.
The Fisher Exact-test was applied to frequency data.
The Kruskal-Wallis nonparametric ANOVA test was applied to motor activity data to determine intergroup differences

All tests were two-sided and in all cases p < 0.05 was accepted as the lowest level of significance.

Group means were calculated for continuous data and medians were calculated for discrete data (scores) in the summary tables. Test statistics were calculated on the basis of exact values for means and pooled variances. Individual values, means and standard deviations may have been rounded off before printing. Therefore, two groups may display the same printed means for a given parameter, yet display different test statistics values.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
Mortality
No mortality occurred during the study period that was considered to be related to treatment with the test substance.

One female at 300 mg/kg (no. 66) was sacrificed after having a total litter loss (her two pups went missing on Day 2 of lactation).

Clinical signs
No clinical signs of toxicity were noted during the observation period.

Incidental findings that were noted for control and/or treated animals included scabbing on both cheeks, scales and scabs on the neck and alopecia. These findings occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study. At the incidence observed, these were considered not to be toxicologically relevant.

Functional observations
Hearing ability, pupillary reflex, static righting reflex and grip strength were normal in all selected animals.

The variation in motor activity did not indicate a relation with treatment. All groups showed a similar habituation profile with high activity in the first interval that decreased over the duration of the test period.

Body weights
Body weights and body weight gain of treated animals remained in the same range as controls over the treatment period.

Food consumption
Food consumption before or after allowance for body weight was similar between treated and control animals.

Haematology
No toxicologically relevant changes occurred in haematological parameters of treated rats.

Any statistically significant changes in haematology parameters occurred in the absence of a dose-related trend and means remained within the range considered normal for rats of this age and strain. These changes consisted of a lower haemoglobin and prothrombin time (PT) in males at 300 mg/kg and higher relative monocyte counts in males at 100 mg/kg.

Clinical biochemistry
No toxicologically relevant changes occurred in clinical biochemistry parameters of treated rats.

The higher bilirubin level of females at 1000 mg/kg remained within the range considered normal for rats of this age and strain and occurred in the absence of any supportive morphological or clinical biochemistry changes. No toxicological relevance was therefore ascribed to this change.

Macroscopic examination
Macroscopic observations at necropsy did not reveal any alterations that were attributable to treatment.

Incidental necropsy findings noted for control and treated animals remained within the range of findings considered normal for rats of this age and strain, did not show a dose-related incidence trend, or supportive treatment-related histopathological lesions. Therefore, all observed macroscopic findings were not considered to be toxicologically relevant.

Organ weights
No toxicologically relevant changes were noted in organ weights and organ to body weight ratios.

The statistically significantly lower absolute seminal vesicle weight of males at 100 and 300 mg/kg occurred in the absence of a dose-related trend and means remained within the range considered normal for rats of this age and strain. These changes were therefore considered to be of no toxicological relevance.

Microscopic examination
There were no treatment-related microscopic findings.

There were no microscopic findings in any of the animals suspected of infertility which could explain their lack of reproductive performance.

The spermatogenic staging profiles were normal for all animals assessed.

The recorded microscopic findings were within the range of background lesions encountered in Wistar (Han) rats of this age in this type of study and occurred at similar incidences and severity in both control and treated rats.
Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects were seen any in either sex in any of the treatment groups.
Critical effects observed:
not specified
Conclusions:
The repeat dose No Observed Adverse Effect Level (NOAEL) is equal to or greater than the high dose of 1000 mg/kg per day.
Executive summary:

A combined 28-day repeated dose toxicity study with the reproduction/developmental toxicity screening test was conducted with Alkylated Naphthalene in rats by oral gavage.

The study was based on OECD 422, Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test, March 1996.

Rationale for dose levels

Based on the results of a 10-day dose range finding study, the dose levels for this combined 28-day oral gavage study with reproduction/developmental toxicity screening test were selected to be 100, 300 and 1000 mg/kg.

 

Study outline

After acclimatization, four groups of ten male and ten female Wistar Han rats were exposed by oral gavage to the test substance at 0, 100, 300 and 1000 mg/kg.

Males were exposed for 29 days, i.e. 2 weeks prior to mating, during mating, and up to termination. Females were exposed for 40 - 54 days, i.e. during 2 weeks prior to mating, during mating, duringpost-coitum, and during at least 4 days of lactation.

 

Evaluated parameters

The following observations and examinations were evaluated: mortality / viability, clinical signs (daily), functional observations and locomotor activity (end of treatment), body weight and food consumption (at least at weekly intervals), clinical pathology (end of treatment), macroscopy at termination, organ weights and histopathology on a selection of tissues, and reproduction/developmental parameters, consisting of mating, fertility and conception indices, precoital time, number of corpora lutea and implantation sites, gestation index and duration, parturition, maternal care, sex ratio and early postnatal pup development (mortality, clinical signs, body weights and macroscopy).

Results/discussion

 

Parental results:

No parental toxicity was observed up to the highest dose level tested (1000 mg/kg).

 (reproduction and development results are reported in separate endpoint study records)

Treatment with Alkylated Naphthalene by oral gavage in male and female Wistar Han rats at dose levels of 100, 300 and 1000 mg/kg revealed no parental toxicity up to 1000 mg/kg.

 

Based on these results, a parental No Observed Adverse Effect Level (NOAEL) of at least 1000 mg/kg was derived.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
1 000 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
High Quality GLP study following current guidelines.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Treatment of male and female Wistar rats by oral gavage at dose levels of 100, 300 and 1000 mg/kg body weight/day revealed no parental toxicity.

Alkylated naphthalene has very low toxicity and the testing established a NOAEL equal to or greater than the maximum dose of 1000 mg/kg/day.

Alkylated Naphthalene, EC Number 700-826-8 is a close structural analog of alkyl naphthalene. The substances have similar chemical and physical properites and the repeat dose toxicity testing for Alkylated Naphthalene, EC Number 700-826-8 can be used as read-across to alkyl naphthalene.

In addition, though a full study report is not available, a 28-day rat dermal study with a substance with the same EC number as Alkylnaphthalene was obtained during the Inquiry Process. This study showed that a 28-day dermal exposure to male and female rats at doses of 0, 125, 500 and 2000 mg/kg produced no mortality or clinical symptoms and the local effect observed was a minimal benign epidermal hyperplasia.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
A well-conducted GLP OECD 422 study without significant deficiencies established a NOAEL. of >= 1000 mg/kg/day.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
Due to low vapor pressure (< 2.2 × 10-6 mm Hg at 20 °C) and high boiling point (> 200 °C), the inhalation route is not considered to be a relevant exposure route to human. In addition, the data of acute toxicity by oral is available and sufficient for assessment of acute toxicity of test substance. Thus, the acute inhalation toxicity study can be waived.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
Due to low vapor pressure (< 2.2 × 10-6 mm Hg at 20 °C) and high boiling point (> 200 °C), the inhalation route is not considered to be a relevant exposure route to human. In addition, the data of acute toxicity by oral is available and sufficient for assessment of acute toxicity of test substance. Thus, the repeat dose inhalation toxicity study can be waived.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
It is considered that exposure via the oral route is considered a worst case exposure whereby the systemic availability of the substance is considered to be maximised. Exposure via the dermal route is expected to be considerably less than via the oral route due to lack of absorption under expected exposure conditions. In addition, though a full study report is not available, a 28-day rat dermal study with a substance with the same EC number as Alkylnaphthalene was obtained during the Inquiry Process. This study showed that a 28-day dermal exposure to male and female rats at doses of 0, 125, 500 and 2000 mg/kg produced no mortality or clinical symptoms. Thus, the repeat dose dermal toxicity study can be waived.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
It is considered that exposure via the oral route is considered a worst case exposure whereby the systemic availability of the substance is considered to be maximised. Exposure via the dermal route is expected to be considerably less than via the oral route due to lack of absorption under expected exposure conditions. In addition, though a full study report is not available, a 28-day rat dermal study with a substance with the same EC number as Alkylnaphthalene was obtained during the Inquiry Process. This study showed that a 28-day dermal exposure to male and female rats at doses of 0, 125, 500 and 2000 mg/kg produced no mortality or clinical symptoms and the local effect observed was a minimal benign epidermal hyperplasia. Thus, the repeat dose dermal toxicity study can be waived.

Justification for classification or non-classification

Alkylated Naphthalene has very low toxicity and, with an established NOAEL equal to or greater than the maximum dose of 1000 mg/kg/day, classification of repeat dose effects according to CLP (Regulation EC No 1272/2008) is not required.

Alkylated Naphthalene, EC Number 700-826-8 is a close structural analog of alkyl naphthalene. The substances have similar chemical and physical properites and the repeat dose toxicity testing for Alkylated Naphthalene, EC Number 700-826-8 can be used as read-across to alkyl naphthalene.