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Toxicological information

Repeated dose toxicity: dermal

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Administrative data

Endpoint:
sub-chronic toxicity: dermal
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Justification for type of information:
Concawe believes that dermal is the most relevant exposure route, and is sufficiently robust, to identify any potential hazards from repeated exposures to petroleum products to be able to adequately manage the potentially associated risks. However, the primary objective of the testing required for REACH is the identification of hazard, for which the default exposure route under the regulation is oral as this is considered to maximise systemic exposure. To address the regulatory exposure route issue, Concawe will review the current data base for evidence of systemic toxicity after dermal exposure and will also conduct a number of oral OECD 422 studies on prioritized substances in each relevant petroleum category. The document attached provides a concise overview of the information to further support the dermal route of exposure and proposed additional work, as part of a larger testing strategy (the strategy document can be found in Annex 13).
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1997

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 411 (Subchronic Dermal Toxicity: 90-Day Study)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Test material form:
other: low viscosity liquid hydrocarbon
Details on test material:
Test substance: Hydrodesulfurized kerosine

The Hydrodesulfurized kerosine had the following properties.

Boiling point 148.9 °C (300 °F)
Specific gravity 0.825 @ 60 °F
Melting point Not applicable
% volatile 100
Vapour pressure 0.4 mm Hg @ 68 °F
Evaporation rate (water = 1) Slower
Vapour density (air = 1) 4.7
Viscosity 1.3 - 2.2 cSt @ 100 °F
% solubility in water Negligible
Pour point -34.4 °C (-30 °F)
pH Not determined
Appearance/odour Clear liquid with hydrocarbon odour


The vehicle used was Squibb mineral oil.

For dosing, mixtures of hydrodesulfurized kerosine were
prepared in the mineral oil at concentrations of 20, 40 and
60% (v/v)

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female

Administration / exposure

Vehicle:
other: Squibb mineral oil
Details on exposure:
Route of Administration: dermal
Duration of treatment / exposure:
Six hours each day
Frequency of treatment:
Daily, five days per week for 13 weeks
Doses / concentrations
Remarks:
Doses / Concentrations:
165, 330 & 495 mg/kg/day
Basis:

No. of animals per sex per dose:
12 female and 12 male
Control animals:
yes, concurrent vehicle

Examinations

Observations and examinations performed and frequency:
Animals were observed for clinical signs prior to dosing and 1, 6 and 24 hours after the first dose. Subsequently, observations were made prior to each dose being applied.
Prior to the administration of each dose, the treated skin site was evaluated for dermal irritation using the Draize scoring method. Body weights were recorded prior to the first dose and weekly thereafter. An ophthalmic examination was conducted on each rat prior to application of the first dose and again prior to sacrifice at the end of the study.
Other examinations:
During the week prior to the first dose, each rat was subjected to a functional observation battery (FOB). The FOB was conducted again 1, 6 and 24 hours after the first dose and at 7 and 14 days. During the study, the FOB, motor activity and startle response testing was conducted on all rats at weeks 4, 8 and 12. 
Statistics:
Normally-distributed in-life data (parametic) were analyzed for test substance effects by analysis of variance and pairwise comparisons made between groups using Dunnett's test. Nonparametric data (nonhomogenous as determined by Bartlett's) were analyzed using a modified t-test. Statistical significance was reported at the P < 0.05 level. Statistical analyses of neurobehavior data (FOB and motor activity) are described in the results section.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Description (incidence and severity):
except skin irritation at application site
Dermal irritation:
effects observed, treatment-related
Description (incidence and severity):
slight dermal irritation in all male groups
Mortality:
no mortality observed
Description (incidence):
except skin irritation at application site
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
spleen/body and spleen/brain weight

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
>= 495 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No significant effects other than irritation at the site of application
Dose descriptor:
LOEL
Effect level:
ca. 165 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male
Basis for effect level:
other: slight dermal irritation seen in all male treated groups

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

All animals survived until scheduled termination. There were no test substance-related effects on survival, clinical observations (apart from skin irritation), neurobehavioral signs or ophthalmological findings. The only clinical observations during the study were related to skin irritation at the application site. There was a generally dose-related increase in the incidence and severity of erythema, oedema, epidermal scaling, scab formation, thickening of the skin and ulceration at the treated site. Males seemed to be more sensitive than females.

The FOB screen did not demonstrate any substance-related effects. The areas monitored were: behavioural parameters, including autonomic, muscle tone and equilibrium, sensorimotor responses, central nervous system. In addition the test substance had little effect on motor activity or startle response.

Growth rates were unaffected by treatment.

At necropsy no substance-related observations were made for males in any group.
 In the females there was a suggestion of a possible treatment-related effect which occurred in 7 rats across all groups and consisted of skin crusts or ulceration at the site of application of test material.

Haematological and serum clinical parameters were unaffected by treatment.

The only organ weight effects noted were an increase in spleen/body weight and spleen/brain weight ratios in the high dose group females at the 13 week necropsy and an increase in absolute spleen weight in the same dose group females after the 4 weeks recovery period.
 Since there were no associated microscopic or clinical chemical findings, these differences were not considered to be of biological relevance.

There were no treatment-related microscopic changes in the tissues examined with the exception of the findings in the skin.
 The skin observations were minimal in nature with a severity score less than 1 on a 1 [low] to 4 [severe] scale.
The findings included acanthosis, ulceration, parakeratosis, chronic active inflammation and hyperkeratosis.
 The males were affected at all doses, however, the effects indicated very little irritation. Recovery group animals revealed complete recovery in the females and minimal hyperkeratosis in the high dose group males.
No effects were found in the animals subjected to a detailed
 neuropathological examination.

Applicant's summary and conclusion

Conclusions:
All animals survived until scheduled termination. There were no test substance-related effects on survival, clinical observations (apart from skin irritation), neurobehavioral signs or ophthalmological findings.
There was a generally dose-related increase in the incidence and severity of various skin conditions at the treated site. Males seemed to be more sensitive than females.
Executive summary:

During the study, Hydrodesulfurized kerosine was applied at concentrations of 20, 40 or 60% (v/v) at a rate of 1 ml/kg/day to the shorn intrascapular region of groups of 12 individually housed male and female, Sprague-Dawley rats (aged 7-9 weeks). This was equivalent to doses of test material of 165, 330 or 495 mg/kg/day. Dosing was continued for five days a week for 13 weeks. In addition a group of 12 male and 12 female rats of similar age were administered mineral oil at a dose rate of 1 ml/kg/day; these animals served as vehicle controls. 12 rats/sex/group each in the vehicle controls and high dose group were maintained for a 4-week recovery period. Ingestion of the test material was prevented by using a collar and removal of any residual test or control material from the skin. Animals were observed for clinical signs prior to dosing and 1, 6 and 24 hours after the first dose. Subsequently, observations were made prior to each dose being applied.

Prior to the administration of each dose, the treated skin site was evaluated for dermal irritation using the Draize scoring method. Body weights were recorded prior to the first dose and weekly thereafter. An ophthalmic examination was conducted on each rat prior to application of the first dose and again prior to sacrifice at the end of the study. During the week prior to the first dose, each rat was subjected to a functional observation battery (FOB). The FOB was conducted again 1, 6 and 24 hours after the first dose and at 7 and 14 days. During the study, the FOB, motor activity and startle response testing was conducted on all rats at weeks 4, 8 and 12. At week 14 blood samples were collected from 12 animals/sex/group. Full necropsies were performed at week 14 on 6 rats/sex/group and at week 18 on the recovery rats (vehicle and high dose groups). Each full necropsy included an examination of the external surface of the body and its contents. The remaining six rats of each group were anesthetized with an intraperitoneal injection of Pentothal and transcardially perfused in-situ using 10% neutral-buffered formalin and given a limited necropsy. For these rats, no organs were weighed and specific tissues were also collected for subsequent microscopic testing.

There was a generally dose-related increase in the incidence and severity of various skin conditions at the treated site. Males seemed to be more sensitive than females as they were affected at all doses, however, the effects indicated very little irritation. Recovery group animals revealed complete recovery in the females and minimal hyperkeratosis in the high dose group males. At necropsy no substance-related observations were made for males in any group. In the females there was a suggestion of a possible treatment-related effect which occurred in 7 rats across all groups and consisted of skin crusts or ulceration at the site of application of test material. Haematological and serum clinical parameters were unaffected by treatment. 

All animals survived until scheduled termination. There were no test substance-related effects on survival, clinical observations (apart from skin irritation), neurobehavioral signs or ophthalmological findings. The NOEL for systemic toxicity was >495 mg/kg/day. The LOEL for slight dermal irritation was 165 mg/kg/day.