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Genetic toxicity: in vivo

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in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
This study is used for read-across and therefore has been assigned a reliability of 2 (reliable with restrictions). The study, if used in support of terephthalic acid, has a reliability of 1 (reliable without restriction). Guideline study performed under GLP requirements.

Data source

Referenceopen allclose all

Reference Type:
study report
Reference Type:
secondary source
SIDS Initial Assessment Report for the 12th SIAM, Paris, France, June 2001
Bibliographic source:
UNEP Publications

Materials and methods

Test guideline
according to guideline
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
Type of assay:
micronucleus assay

Test material

Constituent 1
Chemical structure
Reference substance name:
Terephthalic acid
EC Number:
EC Name:
Terephthalic acid
Cas Number:
Molecular formula:
Terephthalic acid
Details on test material:
Terephthalic acid was supplied by the Amoco Corporation.
Terephthalic acid, a white solid (powder), lot no. SBJ-4972, purity 99.9%. The substance was stored at room temperature, protected from light and moisture.

Test animals

Details on test animals or test system and environmental conditions:
Male and female ICR mice were obtained from Harlan Sprague Dawley, Inc. in two batches. At study initiation mice were 6-8 weeks old. Pilot study mouse weights were: males 29.5-34.1 g; females 25.2-27.4 g. Micronucleus assay mouse weights were: males 25.6-30.4 g; females 23.9-28.1 g.
Mice were quarantined for 5 days. The animal room was maintained at a temperature of 72±3°F, 50±20% relative humidity and a 12 hour light/dark cycle. Mice were housed in same sex groups of 5 in polycarbonate cages on racks. Hardwood chips were used as bedding. Food (Harlan TEKLAD certified Rodent 7012C) and tap water (Washington Suburban Sanitary Commission) were provided ad libitum.
Mice were numbered and identified by ear tag.

Administration / exposure

Route of administration:
Corn oil. The vehicle was chosen as it permitted preparation of the highest soluble or workable stock solution, up to 100 mg/ml (compared to 0.5% CMC in water).
Details on exposure:
Mice were given a single intraperitoneal injection of the test substance, or vehicle alone. All mice were weighed immediately prior to dose administration and the dose volume based on individual body weights. Injections were kept to a constant volume of 20 ml/kg body weight. Additional animals (5/sex/group) were treated with vehicle or 800 mg/kg TPA and sacrificed at 48 hours. An additional group of 5 males and 5 females were dosed with 800 mg/kg TPA as a replacement group in case of mortality.
Duration of treatment / exposure:
Pilot study & Toxicity study: mice were observed for signs of toxicity for 3 days after administration.
Micronucleus study: single injection, mice were sacrificed 24 hours later. Additional mice from the vehicle control and high dose groups were sacrificed 48 hours after dose administration.
Frequency of treatment:
Single injection
Post exposure period:
Pilot study & Toxicity study: 3 days
Micronucleus study: 24 or 48 hours.
Doses / concentrationsopen allclose all
Pilot Study: 1, 10, 100, 1000 and 2000 mg/kg (nominal)
Toxicity Study: 1200, 1400, 1600 and 1800 mg/kg (nominal)
Main Micronucleus Study: 200, 400, and 800 mg/kg (nominal)
No. of animals per sex per dose:
Pilot study: 5 mice/sex received 2000 mg/kg, and 2 males/dose received either 1, 10, 100 or 1000 mg/kg
Toxicity study: 5 mice/sex/dose
Micronucleus study: controls - 10 mice/sex; 200 and 400 mg/kg - 5 mice/sex/dose, 800 mg/kg - 15 mice/sex/per dose, positive controls - 5 mice/sex/dose
Control animals:
yes, concurrent vehicle
Positive control(s):
In the micronucleus study, 5 males and 5 females were injected with cyclophosphamide dissolved in distilled water at a dose of 50 mg/kg.


Tissues and cell types examined:
Bone marrow cells obtained from the femurs.
Details of tissue and slide preparation:
Immediately follow sacrifice, the femurs were exposed, cut just above the knee, and the bone marrow was aspirated into a syringe containing foetal bovine serum. The cells were transferred to a capped centrifuge tube containing approximately 1 ml foetal bovine serum. The cells were pelleted by centrifugation at 100 x g for 5 minutes and the supernatant drawn off. The cells were resuspended and a small drop of bone marrow suspension was spread onto a clean glass slide. Two slides were prepared from each mouse. The slides were fixed in methanol and stained with May-Gruenwald-Giemsa and permanently mounted. Slides were coded prior to analysis.
Evaluation criteria:
2000 polychromatic erythrocytes were scored per slide for the presence of micronuclei. The number of micronucleated normochromatic erythrocytes per 2000 polychromatic erythrocytes was recorded, and the proportion of polychromatic erythrocytes to total erythrocytes over 1000 was recorded.
The test article was considered to induce a positive response if a dose responsive increase in micronucleated polychromatic erythrocytes was observed, and one or more doses were statistically elevated relative to the vehicle control.
Kastenbaum-Bowman tables were used to determine statistical significance at the 5% level.

Results and discussion

Test results
lethargy and piloerection at all doses
Vehicle controls validity:
Negative controls validity:
not examined
Positive controls validity:
Additional information on results:
Pilot study: 3/5 males and 5/5 females died within 2 days administration of 2000 mg/kg. Lethargy and piloerection were noted in males at 1000 mg/kg and males and females at 2000 mg/kg. Tremors were observed in the males at 2000 mg/kg, and convulsions, prostation and crusty eyes were observed in females at this dose. All other animals appeared normal.

Toxicity study: mortality occurred within 3 days of dosing as follows: 2/5 males and 1/5 females at 1200 mg/kg; 4/5 males and 3/5 males at 1400 mg/kg; 2/5 males and 4/5 females at 1600 mg/kg; and 4/5 males and 2/5 females at 1800 mg/kg. Lethargy, piloerection and crusty eyes were seen in all mice at all doses. Tremors were seen in females at 1200 mg/kg, and in males and females at 1400 and 1800 mg/kg. Convulsions were seen in males and females at 1600 and 1800 mg/kg, and prostration in males at 1200 and 1400 mg/kg and males and females at 1600 and 1800 mg/kg. The maximum tolerated dose chosen for the micronucleus assay was 800 mg/kg.

Micronucleus study: 1 male mouse in the 800 mg/kg group was found dead the day after administration, but was replaced. Lethargy and piloerection were seen at all 3 doses in both sexes. Mice treated with vehicle alone and the positive control substance appeared normal throughout the study. Reductions of 2% to 9% in the ratio of polychromatic erythrocytes to total erythrocytes were observed in some of the treated groups compared to controls suggesting that erythropoiesis was not inhibited. There were no significant increases in the number of micronucleated polychromatic erythrocytes per 2000 polychromatic erythrocytes in treated groups compared to controls, irrespective of sex and time of bone marrow collection. The positive control substance induced a significant increase.

Applicant's summary and conclusion

Under the conditions of this study, the test substance did not induce a significant increase in the incidence of micronucleated polychromatic erythrocytes in bone marrow and was concluded to be negative in the mouse micronucleus test.
Executive summary:

The test substance was tested in the mouse micronucleus assay. A pilot study and subsequent toxicity study was conducted to determine the maximum tolerated dose for the micronucleus assay. The test substance was administered in corn oil by a single intraperitoneal injection, at a constant injection volume of 20 ml/kg. Based on mortality and clinical signs observed during the pilot and toxicity studies, the maximum tolerated dose set for the micronucleus study was 800 mg/kg. Clinical signs included lethargy, piloerection, tremors and crusty eyes. In the micronucleus assay, the test substance was administered i.p. at doses of 0, 200, 400 and 800 mg/kg. Bone marrow cells were harvested 24 or 48 hours later. The positive control was cyclophosphamide. No significant increase in micronucleated polychromatic erythrocytes in test article treated groups relative to vehicle controls was observed. Under the conditions of this study, the test substance was concluded to be negative in the mouse micronucleus test.