Glycollic acid

Neurotoxicity

Description of key information

NOEL (neurotoxicity): 600 mg/kg bw/day (male/female). The NOEL is based on 100% glycolic acid dosed (adjusted for 70% purity of the test substance).
No treatment-related effects on neurotoxicity parameters were observed in males or females at any dose (150, 300, or 600 mg/kg bw/day).

Key value for chemical safety assessment

Effect on neurotoxicity: via oral route

Link to relevant study records

Reference

Endpoint:

neurotoxicity: sub-chronic oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2 October 1998 to 13 August 1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Guideline compliant Commission Directive 87/302/EEC, U.S. EPA Pesticide Assessment Guidlines Subdivision F, 82-1 ( 1982), OECD Test Guideline 407, Maff Japan NohSan No. 4200 ( 1985).

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 424 (Neurotoxicity Study in Rodents)

Principles of method if other than guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicology in Rodents)
EPA OPP 82-1 (90-Day Oral Toxicology).

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: Crl:CD (SD) IGS.BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, North Carolina.
- Age at study initiation: 48 days. Birthdated 18 August 1998. Rats were circa 5 weeks old at time of receipt. Group mean bodyweight range at time of allocation to study was 229.5 to 232.6g for males and 163.7 to 165.0g for females.
- Housing: all rats were housed one per cage, sexes separate, in stainless steel, wire-mesh cages suspended above cage boards.
- Diet (e.g. ad libitum): All rats were fed PMI Nutrition International, Inc. Certified Rodent Checkers LabDiet@ 5002 ad libitum.
- Water (e.g. ad libitum): Tap water was provided ad libitum
- Acclimation period: Upon arrival at Haskell Laboratory, the rats were quarantined for six days of the 13-day pretest period.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23" +/- 1°C
- Humidity (%): 50% +/- 10%
- Photoperiod (hrs dark / hrs light): 12-hour light/dark cycle (fluorescent light)

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

Dose solutions were prepared at 15, 30 and 60 mg/mL on a daily basis and administered on same day by gavage in a dose volume of 10 mL/kg bw.
The solutions were administered daily by oral gavage at a dose volume of 10 ml/kg, to achieve dose levels of 150, 300, and 600 mg/kg/day, based on the most recently recorded weight. Dosing solutions were stored refrigerated until used. Dosing solutions stored beyond 14 days after preparation were not administered to animals. Control animals were dosed with commercially-supplied water only.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

HPLC: Hewlett-Packard 1090; UV 210 nm; column: Zorbax® SB-C18, 4.6 mm x 150 mm; 40°C mobile phase: 2.0% acetonitrile/98.0% 3.1 mM H3P04; 1.0ml/min., Injection volume: 4.0 µl
From each dosing solution sample, 1 mL was aliquoted and diluted to 10 mL with high performance liquid chromatography (HPLC) grade water, then mixed. The 0 mg/mL and 15 mg/mL solutions were analyzed without further dilution. The 30 mg/mL and 60 mg/mL samples were further diluted with HPLC grade water to an expected concentration of 1.5 mg/mL active ingredient (a.i.) prior to analysis. Samples submitted for analysis were analyzed the day the solutions were prepared by the testing group.

Duration of treatment / exposure:

90 days.

Frequency of treatment:

Administered daily

Remarks:

Doses / Concentrations:
0, 150, 300 or 600 mg/kg bw/day or vehicle, 15, 30 and 60 mg/mL administered in 10 mL/kg bw volume of water
Basis:
nominal in water

No. of animals per sex per dose:

10 males and females per dose group

Control animals:

yes, concurrent vehicle

Details on study design:

See study design table in "other information section".

- Dose selection rationale: Dose levels for this study were selected based on results from a developmental toxicity study in which glycolic acid was administered by gavage to Crl:CD%R female rats (25/group) on days 7-21 of gestation at daily dose levels of 0, 75, 150, 300, or 600 mg/kg/day.
- Rationale for animal assignment (if not random): Rats were selected for study use on the bases of adequate body weight gain, freedom from any
clinical signs of disease or injury, and a body weight within 20% of the mean within a sex. The selected rats were distributed by computerized, stratified randomization so that there were no statistically significant differences among group body weight means within a sex.

Observations and clinical examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Cage-site examinations to detect moribund or dead rats and abnormal behavior and appearance among rats were conducted at least once daily throughout the study. Moribund and dead rats were submitted for a gross and microscopic examination. At every weighing, each rat was
individually handled and examined for abnormal behavior and appearance. Rats designated for neurotoxicity evaluations had cage-site examinations approximately one to two hours after dosing on test day 1, and approximately one to two hours after dosing on one day during the weeks that the functional observational battery was conducted.

BODY WEIGHT: Yes
- Time schedule for examinations: All rats were weighed once per week during the 90-day feeding phase of the study. In addition, the neurotoxicity substudy rats were weighed on the days of neurotoxicity evaluation.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)/ FOOD EFFICIENCY
The amount of food consumed by each rat over each weighing interval was determined throughout the study. From these determinations and body weight data, mean daily food consumption and mean food efficiency were calculated.

Neurobehavioural examinations performed and frequency:

Functional Observational Battery Test: All rats designated for neurotoxicity assessment were evaluated by the functional observational battery (FOB) test. The rats were subdivided into four replicates tested over a two-day period with an approximately equal representation of each group within a replicate. Rats were observed on test days -3 and -4, prior to test substance administration, to establish their baseline FOB parameters. The FOB was performed prior to dosing on test days 9 and 10, 45 and 46, and 86 and 87.

Motor Activity Test: All rats designated for neurotoxicity assessment were evaluated by the motor activity (MA) test. MA sessions were conducted prior to dosing on the same day as FOB assessments, following FOB evaluations. Rats were indlvidually tested in one of 30 nominally identical, automated activity monitors (Codbourn@).

There were no test substance-related effects or statistically significant differences in forelimb strength, hindlimb grip strength or footsplay for either male or female at any dose. There were no biologically significant, test substance-related effects on the 37 behavioral parameters evaluated for males ot females at any dose. There was a significantly higher incidence of defaecation on the open fields for the males dosed 150, 300, or 600 mg/kg/day that was considered to be spurious. However, there were no statistically significant differences in the incidences of neurobehavioral parameters in females at any dosage.

Sacrifice and (histo)pathology:

Six animals per sex per group that had been orally exposed to 0, 150, 300, or 600 mg/kg/day of the test substance for approximately 13 weeks were randomly selected from the neurobehavioral subset. Six unexposed control animals per sex were also randomly selected as negative controls. On test days 94 and 95, three designated rats/sex/group/day were euthanatized by pentobarbital anesthesia followed by exsanguination and whole body perfusion fixation. Animals were examined grossly at the times of perfusion and dissection. Tissue samples from the nervous system and skeletal muscle were saved from all groups. Only tissues from the control (0 mg/kg/day) and high concentration groups (600 mg/kg/day) were processed for histopathology and examined. Sections of the brain, spinal cord, and skeletal muscle were embedded in paraffin, sectioned at an approximate thickness of 5 pm, and stained with hematoxylin and eosin (HE). Additional sections of brain and spinal cord were sectioned and stained with Luxol fast blue and periodic acid Schiff (LFBFAS). Sections of sciatic, tibial, and sural nerves, gasserian ganglia, dorsal root fibers and ganglia, and ventral root fibers were embedded in glycol methacrylate, sectioned at an approximate thickness of 3 pm, and stained with hematoxylin and eosin.

Positive control:

A positive control study involved collecting sera from animals previously injected with SRBC and the immunosuppressive agent, Cyclophosphamide. Serum was analysed for SRBC-specific IgM antibody.

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

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Behaviour (functional findings):

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

no effects observed

Description (incidence and severity):

Migrated information from 'Further observations for developmental neurotoxicity study'

Details on results (for developmental neurotoxicity):There were no test subtance-related changes in either males or females at any dosage for forelimb or hindlimb grip strentgh, footsplay, motor activity or any of the 37 other neurobehavioral parameters.
Under the conditions of the study, the NOEL for neurobehavioral parameters was 600 mg/kg/day in males and females, based on lack of effects at the highest dose tested. (migrated information)

Details on results:

There were no test subtance-related changes in either males or females at any dosage for forelimb or hindlimb grip strentgh, footsplay, motor activity or any of the 37 other neurobehavioral parameters.

Under the conditions of the study, the NOEL for neurobehavioral parameters was 600 mg/kg/day in males and females, based on lack of effects at the highest dose tested.

The NOEL for this study is based on 100% glycolic acid dosed (adjusted for 70% purity of the test substance).

Dose descriptor:

NOEL

Remarks:

Neurotoxicity

Effect level:

600 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: The FOB evaluations showed no treatment-related effects in either males or females dosed at 150, 300 or 600 mg/kg bw/day.

Gross Observations

- There were no test substance-related gross lesions observed in this study.

Microscopic Findings

- There were no test substance-related microscopic observations in tissues selected for neurotoxicity evaluation. The microscopic lesions observed were minimal changes (axodmyelin degeneration) that typically occurred sporadically in only one or two individual nerve fibers in any given anatomic location. Lesions observed in the high concentration (600 mg/kg/day) group were essentially the same in character and severity as those observed in the control (0 mg/kg/day) group, and have been described as occurring spontaneously in the ratF5. Thus, lesions observed microscopically in this study were judged not to be test substance related.

Mortality

- There were six unscheduled deaths within the neurotoxicity subset of animals. These animals all had pulmonary lesions consistent with accidental administration of gavage fluid into the lungs and were considered accidental deaths.

Conclusions:

There were no test substance-related neuropathologic effects observed in this study. For the neurotoxicity parameters evaluated under the conditions of this study, the no-observed effect level (NOEL) was 600 mg/kg/day, the highest dose tested.

For the neurotoxicity parameters evaluated under the conditions of this study, the non-observed effect level (NOEL) was 600 mg/kg/day, the highest dose tested. The NOEL was based upon the absence of the test-substance-related effects on behavioral or neuropathology evaluations.

Executive summary:

For the neurotoxicity parameters evaluated under the conditions of this study, the non-observed effect level (NOEL) was 600 mg/kg/day, the highest dose tested. The NOEL was based upon the absence of the test-substance-related effects on behavioral or neuropathology evaluations.

Additional information

A Functional Observational Battery Test (FOB) was performed in conjunction with the 90-day oral study in rats: All rats designated for neurotoxicity assessment were evaluated by the functional observational battery (FOB) test. The rats were subdivided into four replicates tested over a two-day period with an approximately equal representation of each group within a replicate. Rats were observed on test days -3 and -4, prior to test substance administration, to establish their baseline FOB parameters. The FOB was performed prior to dosing on test days 9 and 10, 45 and 46, and 86 and 87. In addition, all rats designated for neurotoxicity assessment were evaluated by the motor activity (MA) test. MA sessions were conducted prior to dosing on the same day as FOB assessments, following FOB evaluations. Rats were individually tested in one of 30 nominally identical, automated activity monitors (Codbourn®). There were no test substance-related effects or statistically significant differences in forelimb strength, hindlimb grip strength or footsplay for either male or female at any dose. There were no biologically significant, test substance-related effects on the 37 behavioural parameters evaluated for males or females at any dose. There was a significantly higher incidence of defecation in the open field for the males dosed at 150, 300, or 600 mg/kg/day that was considered to be spurious. However, there were no statistically significant differences in the incidences of neurobehavioral parameters in females at any dosage.

Justification for classification or non-classification

No effects indicative of neurotoxicity were observed in the FOB. No evidence of neurotoxic effects requiring classification were evident in the battery of studies or the reviewed publications included in the dossier. According to Regulation (EC) 1272/2008, Glycolic acid does not warrant any classification.