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Description of key information

Oral:
A NOAEL of 100 mg/kg bw/day was determined in a combined repeated dose/reproduction toxicity study (OECD 422) in rats based on changes in clinical chemistry parameters, changes in organ weights and inflammation of the forestomach mucosa.
Dermal and inhalation:
In accordance with column 2 of REACH Annex IX, the test repeated dose toxicity after dermal exposure (required in section 8.6) does not need to be conducted because there is another repeated toxicity robust study available for the oral route.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
short-term repeated dose toxicity: oral
Remarks:
combined repeated dose and reproduction / developmental screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1995.12.6-1997.6.5
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was conducted according to OECED guidelines and was performed under GLP.
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Crj: CD(SD)
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles river Japan
- Age at study initiation: purchase at 9 weeks old, 1st. administration at 10 weeks old
- Weight at study initiation: male: 356.3-394.4g, female: 213.5-252.9g
- Fasting period before study: 18hr
- Housing: dosing period: stainless hanger gage, one animal/cage, mating period: polycarbonate gage with wood chip
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: one week


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22-26°C
- Humidity (%): 45-65%
- Air changes (per hr): 13 times/hr
- Photoperiod (hrs dark / hrs light):12/12 AM07:00-PM07:00
Route of administration:
oral: gavage
Vehicle:
corn oil
Details on oral exposure:
VEHICLE
- Justification for use and choice of vehicle (if other than water): Corn oil is used generally
- Concentration in vehicle: 0.6, 2 and 6w/v%
- Amount of vehicle (if gavage): 5mL/kg
- Lot/batch no. (if required): V5P5831, nakalai tesque Co.
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
no details given
Duration of treatment / exposure:
Males; for 49 days Females; from 14 days before mating to day 3 of lactation (38 days in total)
Frequency of treatment:
one administration/day
Remarks:
Doses / Concentrations:
0(Vehicle), 30, 100 and 300 mg/kg/day (in corn oil)
Basis:
actual ingested
No. of animals per sex per dose:
Doses is 0, 30, 100 and 300mg/kg. 12 animals per sex per dose.
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: oral, one of the identical exposure route for humans
Positive control:
no details given
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: one time per day
- Cage side observations: general symptom

DETAILED CLINICAL OBSERVATIONS: No
BODY WEIGHT: Yes
- Time schedule for examinations: male:two times/week
female: two times/ week at pre-mating period, in pregant period: day at 0, 4, 7,10, 14, 17 and 21, in lactation period: the day 0 and 4.

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
male: two times/week
female: two times/ week at pre-mating period, in pregnant period: day at 1, 4, 7,10, 14, 17 and 21, in lactation period: the day 1 and 4.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: after dosing period
- Anaesthetic used for blood collection: Yes (identity): Pentobarbital-Na i.p.
- Animals fasted: Yes
- How many animals: All of male
- Parameters checked in table (see below in remarks field) were examined.: WBC, RBC, Hb, Ht, PLT

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood:after dosing period (same time for HEMATOLOGY)
- Animals fasted: Yes
- How many animals:All of male
- Parameters checked in table (see below in remarks field) were examined.: TP, ALB, A/G, Bil, GOT, GPT, TGace, ALP, TG, PL, Giu, BUN, CRE, P, Ca, Na, K, Cl

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes (see below in remarks field)
HISTOPATHOLOGY: Yes (see below in remarks field)
Other examinations:
no details given
Statistics:
no details given
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
Three animals (male and female of 300mg/kg group and male of 30mg/kg group) is died by the accident at administration. Salivation was observed in 4-9(/12) animals at male 300 mg/kg on and after day 36. Salivation was observed immediately after administration, and continued about 30 min.

BODY WEIGHT AND WEIGHT GAIN
No stat. sig. difference from controls.

FOOD CONSUMPTION AND COMPOUND INTAKE
No stat. sig. difference from controls except one case (male 30 mg/kg, day 49, increase in consumption).

FOOD EFFICIENCY
Not examined

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
Not examined

OPHTHALMOSCOPIC EXAMINATION
Not examined

HAEMATOLOGY
No stat. sig. difference from controls.

CLINICAL CHEMISTRY
Males: Decrease of total cholesterol and BUN, increase of triglyceride at 300 mg/kg (p<0.05). Decrease of A/G ratio at 100 mg/kg (p<0.05). See Table 1 in overall remarks

URINALYSIS
Not examined

NEUROBEHAVIOUR
Not examined

ORGAN WEIGHTS
Male: Increase in kidney weight and adrenal weight at 100 mg/kg (absolute) (p<0.05), Increase in adrenal weight at 300 mg/kg (relative) (p<0.05)
Female: No stat. sig. difference from controls
See Table 2 in overall remarks

GROSS PATHOLOGY
hyperplasia(male:11/11, female 8/12) at forestomach mucosa (in 300mg/kg, terminal sacrifice)

HISTOPATHOLOGY: NON-NEOPLASTIC
See Table 3, Table 4, Table 5 in overall remarks.
Dose descriptor:
NOEL
Effect level:
30 other: mg/kg
Sex:
male
Basis for effect level:
other: hypertrophy of Gastric mucosa, 1/12
Dose descriptor:
NOEL
Effect level:
100 other: mg/kg
Sex:
female
Basis for effect level:
other: hypertrophy of Gastric mucosa, 9/12
Dose descriptor:
NOAEL
Effect level:
100 other: mg/kg
Sex:
male/female
Basis for effect level:
other: hypertrophy of Gastric mucosa, 12/12
Critical effects observed:
not specified

NOAEL : Male = 100 mg/kg bw

Female = 100 mg/kg bw

Relative and/or absolute adrenal and/or kidney(s) weigh increase was observed in male 100 and/or 300mg/kg group, but no histopathological change was observed, so the author excluded this observation. Squeamous hyperplasia was observed in only one male of 100 mg/kg group, and 8/12 females of 300mg/kg.

Therefore, the NOAEL was determined to be 100mg/kg in both sex.

Conclusions:
A NOAEL of 100 mg/kg bw/day was determined in a combined repeated dose/reproduction toxicity study (OECD 422) in rats based on decreased clinical chemistry parameters, changes in organ weights and inflammation of the forestomach mucosa.
Executive summary:

Tetrahydromethylphthalic anhydride (MTHPA) was administered by gavage at doses of 0, 30, 100 and 300 mg/kg/day for 49 days in males and from 14 days before mating to day 3 of lactation in females (total number of 38 days). All animals survived at all treated group, except three animals died by accident (one female in 30 mg/kg, one male in 300 mg/kg and one female in 300 mg/kg group). Salivation was transiently observed in males of 300 mg/kg group at the day 36-49. Histopathological examination revealed squamous hyperplasia of the forestomach in both sexes of the 300 mg/kg group, epithelial vascular change, edema and cellular inflammation of the forestomach in males of the 300 mg/kg group, and erosion of the forestomach in females of 300 mg/kg group. There were no adverse effects on body weight and food consumption. There were no alterations related to tetrahydromethyl-1, 3-isobenzofuranedione on hematological examination. Decreased total cholesterol and BUN and increased triglyceride were observed in males of the 300 mg/kg. As a gross finding, mucosal thickening of the forestomach was found in both sexes of the 300 mg/kg group. Increased adrenal weights were observed in males of the 300 mg/kg group.

The major toxicity was inflammation of stomach mucosa. On the basis of this study, NOEL is 30mg/kg/day (male), 100mg/kg/day (female) and NOAEL is considered to be100 mg/kg/day for both sexes.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
100 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
This study was conducted according to OECD guidelines and was performed under GLP.

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records
Reference
Endpoint:
repeated dose toxicity: inhalation
Data waiving:
other justification
Justification for data waiving:
other:
Critical effects observed:
not specified
Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Link to relevant study records
Reference
Endpoint:
repeated dose toxicity: inhalation
Data waiving:
other justification
Justification for data waiving:
other:
Critical effects observed:
not specified
Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Link to relevant study records
Reference
Endpoint:
repeated dose toxicity: dermal
Data waiving:
other justification
Justification for data waiving:
other:
Critical effects observed:
not specified
Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Link to relevant study records
Reference
Endpoint:
repeated dose toxicity: dermal
Data waiving:
other justification
Justification for data waiving:
other:
Critical effects observed:
not specified
Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Oral:

In the key study (Izumi, 1997), tetrahydromethylphthalic anhydride (MTHPA) was administered by gavage at doses of 0, 30, 100 and 300 mg/kg/day for 49 days in males and from 14 days before mating to day 3 of lactation in females (total number of 38 days). All animals survived at all treated group, except three animals died by accident (one female in 30 mg/kg, one male in 300 mg/kg and one female in 300 mg/kg group). Salivation was transiently observed in males of 300 mg/kg group at the day 36-49. Histopathological examination revealed squamous hyperplasia of the forestomach in both sexes of the 300 mg/kg group, epithelial vascular change, edema and cellular inflammation of the forestomach in males of the 300 mg/kg group, and erosion of the forestomach in females of 300 mg/kg group. There were no adverse effects on body weight and food consumption. There were no alterations related to tetrahydromethyl-1, 3-isobenzofuranedione on hematological examination. Decreased total cholesterol and BUN and increased triglyceride were observed in males of the 300 mg/kg. As a gross finding, mucosal thickening of the forestomach was found in both sexes of the 300 mg/kg group. Increased adrenal weights were observed in males of the 300 mg/kg group.

The major toxicity was inflammation of stomach mucosa. On the basis of this study, NOEL is 30mg/kg/day (male), 100mg/kg/day (female) and NOAEL is considered to be100 mg/kg/day for both sexes.

No 90 day toxicity study with tetrahydromethylphthalic anhydride (MTHPA) is available. Taken all data from MTHPA and structural analogue substances together, a new 90 day toxicity study with MTHPA is not required and not in line with animal welfare ideas. The data available for chemically almost identical substances in different species and for exposure periods of 90 days support the findings noted in OECD 422 study taking the time extrapolation factor into account. Therefore, the OECD 422 study is considered to represent a reliable basis for DNEL derivation for MTHPA.

Dermal and inhalation:

In accordance with column 2 of REACH Annex IX, the test repeated dose toxicity after dermal exposure (required in section 8.6) does not need to be conducted because there is another repeated toxicity robust study available for the oral route (see IUCLID5 section 7.5.1).

The most relevant exposure route of this substance to investigate systemic toxic effects is oral. In case of inhalation or dermal exposure, sensitising and irritating effects occur before systemic toxicity becomes relevant.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
This study was conducted according to OECD guidelines and was performed under GLP.

Justification for classification or non-classification

On the basis of the data submitted, classification of tetrahydromethylphthalic anhydride (MTHPA) as harmful and labelling with Xn, R 48/22 (Harmful: danger of serious damage to health by prolonged exposure if swallowed) according to the criteria given in Directive 67/548/EEC and with STOT rep. exp. cat 2 according to Annex VI of CLP (GHS) (1272/2008/EC) is not justified.