Phthalic anhydride

Endpoint summary

Description of key information

Chronic oral feeding studies over 2 years in rats and mice including dose finding studies over 7 weeks were conducted by the NCI (National Cancer Institute) for the evaluation of a possible carcinogenicity of phthalic anhydride.
In the 7 weeks dose finding study groups of 5 rats and 5 mice of each sex were administered feed containing 0, 6.200, 12.500, 25.000 or 50.000 ppm phthalic anhydride. The lowest dose at which histopathologic findings were observed in male and female rats was 25.000 ppm (ca. 2500 mg/kg bw). At this dose, trace amounts of centrilobular cytoplasmic vacuolation were seen in the livers of 4 males; however, tissues were essentially normal in both males and females at 50.000 ppm (5000 mg/kg bw). Tissues were essentially normal also in male and female mice at 50.000 ppm.
In the chronic 2 years study 50 male and female rats each (20 male and 20 female rats as control) were fed doses of the test substance of 0, 7.500, or 15.000 ppm (ca. 0, 500, 1000 mg/kg bw/d for 102-106 consecutive weeks, followed by sacrifice, necropsy and histopathological examination of major organs and tissues. In addition 50 male and female mice each (20 male and 20 female mice as control) were fed daily doses of the test substance of 0, 25.000, or 50.000 ppm (ca. 0, 3570, 7140 mg/kg bw/d for 32 weeks. From week 32 to weeks 104 the daily doses were reduced to 0, 12.500 and 25.000 ppm for male mice and to 0, 6.250 and 12.500 ppm to female mice. After the termination of the study on week 104, the animals were sacrificed and necropsy and histopathological examination were performed. No hematology and no clinical chemistry endpoints were examined.
Severe chronic inflammatory, degenerative, or proliferative lesions frequently seen in aged rats and mice occurred with approx. equal frequency and severity in the dosed and control groups of animals. No tumors occurred in the rats and mice of either sex at incidences that could be clearly related to the administration of the test substance.

No reliable studies are available using the dermal and respiratory routes of exposure.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No hematology, urinalysis or clinical chemistry analyses were performed.

Principles of method if other than guideline:

50 male and female rats each (20 male and 20 female rats as control) were fed doses of the test substance of 0, 7.500, or 15.000 ppm (ca. 0, 500, 1000 mg/kg bw/d for 102-106 consecutive weeks, followed by sacrifice, necropsy and histopathological examination of major organs and tissues.

GLP compliance:

not specified

Specific details on test material used for the study:

Elemental analysis was performed and showed, together with the infrared spectrum, an authentic standard.

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: NCI Frederick Cancer Research Center animal farm, Maryland
- Age at study initiation: 6 weeks
- Weight at study initiation: males: 90-105 g; females: 80-95 g
- Fasting period before study: not adequate
- Housing: 4 rats per cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum, acidified to pH 2.5
- Acclimation period: 2 weeks

DETAILS OF FOOD AND WATER QUALITY:

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22-24°C
- Humidity (%): 45-55%
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12 hr per day cycle

Route of administration:

oral: feed

Vehicle:

other: diet

Details on oral exposure:

Based on prelimary studies with 7 week exposure via food, the doses for the chronic studies were determined. 10% depression in body weight was taken as the major criterion for the extimation of MTD's.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses by Frederick Cancer Research Center indicated that when phthalic anhydride was mixed with Lab Meal at a concentration of 15,000 ppm and stored at room temperature for 2 weeks, the loss was 2.59% (372 ppm) per day. Test diets containing phthalic anhydride were thus prepared fresh every 1 to 1.5 weeks. The diets were routinely stored at 5°C until used.

Duration of treatment / exposure:

105 week

Frequency of treatment:

daily

Dose / conc.:

0 ppm

Dose / conc.:

7 500 ppm

Remarks:

ca. 500 mg/kg bw/d

Dose / conc.:

15 000 ppm

Remarks:

ca. 1000 mg/kg bw/d

No. of animals per sex per dose:

50 male and 50 female rats

Control animals:

yes, concurrent no treatment

Details on study design:

Post-exposure period: no

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
Daily observations for sick, tumour bearing and moribund animals, twice daily checked for deaths.
Clinical examination and palpation for masses were performed each month.

BODY WEIGHT: Yes
- Time schedule for examinations: at least once per month

Sacrifice and pathology:

At the end all animals were killed using CO2 inhalation and necropsied. Necropsies were also performed on all animals found dead, unless precluded by autolysis or severe cannibalization.

gross and microscopic examination of: skin, lungs and bronchi, trachea, bone marrow (femur), spleen, lymph nodes (mesenteric and submandibular), thymus, heart, salivary glands (patrotid, sublingual, and submaxillary), liver, pancreas, esophagus, stomach (glandular and nonglandular), small and large intestines, kidneys, urinary bladder, pituitary, adrenal, thyroid, parathyroid, pancreatic islets, testis, prostate, mammary gland, uterus, ovary, brain (cerebrum, and cerebellum), and all tissue masses. Peripheral blood smears were made for all animals, whenever possible.

Statistics:

Data recorded in an automatic data processing system, the Carcinogenesis Bioassay Data System.
Probabilities of survival were estimated by the product-limit procedure of Kaplan and Meyer (1958). A possible dose-related effect on survival was investigated with teh method of Cox (1972 and Tarone's (1975) extensions.
Incidence of neoplastic or nonneoplastic lesions is given as the ratio of animals bearing such lesions to the number without. As part of this analysis the one-tailed Fischer exact test (Cox, 1975) and other tests were used.

Description (incidence and severity):

Arched back, rough hair coat, ulceration, and corneal opacity occurred only in dosed groups, but at low incidences.

Description (incidence):

No statistical significant difference in mortality was observed in any group. Survival male rats: high-dose group 36/50 (72 %) low-dose group 44/50 (88), control group 14/20 (70 %) Survival female rats: high-dose group 41/50 (82 %), low-dose group 42/50 (84 %), control group 17/20 (85 %)

Description (incidence and severity):

The mean body weights of the high-dose males were lower than the controls from week 13 to the end of the study, but the decrease was never more than 10%. Mean body weights of the low-dose males and both the low- and high-dose females were essentially unaffected by the test compound.

Description (incidence and severity):

Severe chronic inflammatory, degenerative, or proliferative lesions frequently seen in aged rats occurred with approx. equal frequency and severity in the dosed and control groups of animals.

Description (incidence and severity):

By inspection, there appeared to be no difference between the dosed and control groups in frequency or distribution of neoplasms, except for malignant lymphoma in the female rats. The incidence in the control females was 1/20; in low-dose females 11/50; in high-dose females 4/50. Due to the high and fluctuating incidence of this type of malignant lymphoma in control F344 rats, the apparent differences in incidences of the tumor in the dosed and control groups were not considered to be compound related.

Key result

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: The NOAEL = 500 mg/kg/day, based on the reduced body-weight gain (<10%).

Critical effects observed:

no

F344 rats (50/sex/group) were fed diets containting 7500 or 15,000 ppm phthalic anhydride for 105 weeks (approx. 500 and 1,000 mg/kg bw/day). The observation that the test compound is unstable (2.59% loss of activity per day at room temperature) has to be noted, although this is of minor relevance because the diet was prepared fresh every 1 to 1-1/2 weeks and the diet was stored at 5 degree Celsius, consequently the hydrolysis is assumed to be lower than 26%.

Executive summary:

50 male and female rats each (20 male and 20 female rats as control) were fed daily doses of the test substance of 0, 7.500, or 15.000 ppm (ca. 0, 500, 1000 mg/kg bw/d for 102-106 consecutive weeks, followed by sacrifice, necropsy and histopathological examination of major organs and tissues.

The NOAEL = 500 mg/kg/day, based on the reduced body-weight gain (<10%).

reference: Huff, 1984; Kluwe, 1986; NCI, 1979

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

500 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

Scientifically acceptable - but no hematology, urinalysis or clinical chemistry analyses were performed.

System:

other: The NOAEL = 500 mg/kg/day, based on the reduced body-weight gain (<10%).

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

In the chronic repeated oral toxicity study severe chronic inflammatory, degenerative, or proliferative lesions frequently seen in aged rats and mice occurred with approx. equal frequency and severity in the dosed and control groups of animals. No tumors occurred in the rats and mice of either sex at incidences that could be clearly related to the administration of the test chemical. Based on the reduced body-weight gain (<10 %) the NOAEL in this study was 500 mg/kg/day for rats. This NOAEL was taken forward for DNEL derivation.

The LOAEL in female mice is 12,019 ppm (approx. 1717 mg/kg/day) and in males 16,346 ppm (approx. 2340 mg/kg/day) due to increased incidences of lung and kidney lymphocytosis, chronic bile duct inflammation and adrenal atrophy and mineralisation of the thalamus.

No valid studies are available using the dermal and respiratory routes of exposure.

Justification for classification or non-classification

Based on the available data a classification according to EU Regulation 1272/2008 is not warranted.