Phthalic acid

Endpoint summary

Description of key information

A chronic feeding study with phthalic anhydride at doses of 7.500, or 15.000 ppm (ca. 500, 1000 mg/kg bw/d for 102-106 consecutive weeks, followed by sacrifice, necropsy and histopathological examination of major organs and tissues) was identified as most relevant for the assessment of repeated dose toxicity of phthalic acid. The NOAEL was 500 mg/kg bw/day in this study, based on reduced body-weight gain (<10%).

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

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

Reference 2

Endpoint:

chronic toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
[Please provide information for all of the points below. Indicate if further information is included as attachment to the same record, or elsewhere in the dataset (insert links in 'Cross-reference' table)]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
“The read-across hypothesis is that different substances give rise to (the same) common compounds to which the organism is exposed.”

Phthalic acid is the hydrolysis product of phthalic anhydride. In contact with water, phthalic anhydride is rapidly hydrolyzed to phthalic acid. Unconjugated phthalic acid was found in the urine of humans exposed to phthalic anhydride by the inhalation route, demonstrating systemic absorption and elimination via the urine and the existence of phthalic acid as the only hydrolysis product in vivo. Therefore, a read-across of systemic toxicity data obtained with the hydrolysis product phthalic acid is considered adequate for phthalic anhydride.
For further information see attached document:
Justification for a read-across between phthalic acid and phthalic anhydride

3. ANALOGUE APPROACH JUSTIFICATION
For further information see attached document:
Justification for a read-across between phthalic acid and phthalic anhydride

Reason / purpose for cross-reference:

read-across source

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

The study results with phthalic anhydride as source fit to phthalic acid as target.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

500 mg/kg bw/day

Study duration:

chronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

There are no repeated dose toxicity studies available for phthalic acid that would allow a scientifically sound risk assessment. In a subacute oral toxicity study 5 male Wistar rats per group were given a powder diet containing phthalic acid at a level of 0.5 or 5% for 34 to 36 days, respectively. Phthalic acid had no effect, even at 5% concentration in the diet. Therefore the NOEL can be considered with approximately > 5000 mg/kg bw (Murakami, 1986). In another subacute oral toxicity study in male Wistar rats the test animals were fed diets containing 2% of phthalic acid for 1 week. No relevant effects were observed in the treated rats. Therefore the NOAEL can be considered with approximately > 2000 mg/kg bw (Oishi, 1980).

Phthalic acid is the hydrolysis product of phthalic anhydride. In contact with water, phthalic anhydride is rapidly hydrolyzed to phthalic acid. Unconjugated phthalic acid was found in the urine of humans exposed to phthalic anhydride by the inhalation route, demonstrating systemic absorption and elimination via the urine and the existence of phthalic acid as the only hydrolysis product in vivo. Therefore, a read-across of systemic toxicity data obtained with the hydrolysis product phthalic acid is considered adequate for phthalic anhydride.

In a chronic feeding study 50 male and female rats per group (20 male and 20 female rats as control) were given phthalic anhydride at doses of 7.500, or 15.000 ppm (ca. 500, 1000 mg/kg bw/d for 102-106 consecutive weeks, followed by sacrifice, necropsy and histopathological examination of major organs and tissues). No hematology and no clinical chemistry endpoints were examined. Severe chronic inflammatory, degenerative, or proliferative lesions frequently seen in aged rats occurred with approximately equal frequency and severity in the dosed and control groups of animals. No tumors occurred in the rats of either sex at incidences that could be clearly related to the administration of the test substance. The NOAEL was 500 mg/kg bw/day in this study, based on reduced body-weight gain (<10%). This NOAEL was taken forward for DNEL derivation.

Justification for classification or non-classification

Based on the available studies, the test substance needs no classification for repeated dose toxicity according to EU Regulation.