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Carcinogenicity

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Description of key information

Oral: NOAEL;  19/mo drinking water; mouse; no neoplastic effects were observed at any exposure level; reliability = 2.
NOT CLASSIFIED

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non GLP. Only used 2 concentrations.
Principles of method if other than guideline:
Mice were administered test substance in drinking water for 78 weeks, after which all mice were given purified water until 83-85 weeks. Necropsy was performed on all mice and organ-weight ratios were determined. Histology was performed on selected tissues.
GLP compliance:
no
Species:
mouse
Strain:
B6C3F1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Japan Inc.
- Age at study initiation: 4 weeks
- Housing: 6-10 mice housed in each aluminum cage, kept in an isorack
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum):Ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24
- Humidity (%): 50%
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: m-PDA dissolved in water, purified by the Milli-Q Reagent Water System, using a magnetic stirrer to prepare a 1% soultion. This solution was stored at 4 degrees C before use. Mice were given 0.04 or 0.02% m-PDA. Each cage of mice was given 30-50 ml (5 ml per mouse) of the solution daily except on Saturday, when double volume was given for 2 days. Remaining water was measured daily so that the mean daily water consumption for each cage of mice could be calculated and these means were averaged to give the daily consumption by mice of each sex in each treatment group. Dosages were increased to 6 mL per mouse at week 39 and then increased to 7 mL at week 45. Treatment continued for 78 weeks, after which all groups were given purified water until 83-85 weeks.
Duration of treatment / exposure:
78 weeks
Frequency of treatment:
Once daily except on Saturdays when double the volume was given for 2 days.
Post exposure period:
5-7 weeks
Remarks:
Doses / Concentrations:
0.02 or 0.04%
Basis: nominal in water
Remarks:
Doses / Concentrations:
23 mg/kg bw/day for females and 19.8 mg/kg bw/day for males at the 0.02 % dose level and 41.8 mg/kg bw/day for females and 38.2 mg/kg bw/day for males at the 0.04 % dose level.
Basis: calculated intake
No. of animals per sex per dose:
59 female and 56 male were used for the 0.04 % concentration and 50 for each sex for the 0.02 % concentration.
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: On the basis of the results of a preliminary 25 week subchronic test using levels of 0.01-0.16 % in the drinking water.
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: No data.

DETAILED CLINICAL OBSERVATIONS: No data.

BODY WEIGHT: Yes.
- Time schedule for examinations was once a week for the first month and once a month for the remainder of the study.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes.
- Time schedule for examinations was daily.

Sacrifice and pathology:
Autopsy performed on all mice. The organ-weight ratios were determined. The liver, lungs, spleen, bone marrow, lyph nodes, pancreas, kidneys, stomach, small and large intestines, heart, urinary bladder, thymus adrenals, slaivary glands, thyroid, brain, pituitary, ovaries, testes, sternum, skin and tumours were fixed in 10% formalin solution, embedded in paraffin, cut into 5um sections and stained routinely with haematoxylin and eosin for histological examination.
Statistics:
The significance of differences in the incidences of tumours, mean values for daily intake of m-PDA, body weights, weights for organs and organ-weight indices were evaluated by the chi-square test.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Description (incidence):
Survival rates at the end of the experiment were more than 86% in all groups. Two to seven mice from each group were killed a few weeks before the end of the treatment mainly due to morbidity from tumours.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Mice in the 0.04% groups of both sexes showed lower rates of weight gain than the controls and the mean weights at the end of treatment were 66 and 83% of the control values, in females and males. Female mice in the 0.02% group also showed lower weight gains than the controls.
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Description (incidence and severity):
Daily intake of drinking water was reduced in mice of the treated groups of both sexes when compared with that of the controls. There was, however, no significant difference in drinking water intake between mice of the 0.02 and 0.04 % groups for either sex. The calculated intake of test substance was 23 mg/kg bw/day for females and 19.8 mg/kg bw/day for males at the 0.02 % dose level and 41.8 mg/kg bw/day for females and 38.2 mg/kg bw/day for males at the 0.04 % dose level.
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Increases of the weight of the liver and spleen relative to body weight in the treated female mice.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
None that significantly differed from control, in most cases numbers were lower for treated groups. The incidences of hepatocellular tumours were significantly lower in all the groups ingesting m-PDA than in the control groups and the incidences of hyperplastic liver nodules and lung adenomas were significantly lowere than those in controls, in control males alone.
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Macroscopically, the skin, liver, spleen, kidneys and bone marrow were darker in colour in mice receiving 0.04% of the test substance.
Histopathological findings: neoplastic:
no effects observed
Dose descriptor:
NOAEL
Effect level:
38.2 mg/kg bw/day
Sex:
male
Basis for effect level:
other: No neoplastic effects observed at any dose level. The calculated intake of test substance was 38.2 mg/kg bw/day for males at the 0.04 % dose level.
Dose descriptor:
NOAEL
Effect level:
41.8 mg/kg bw/day
Sex:
female
Basis for effect level:
other: No neoplastic effects observed at any dose level. The calculated intake of test substance was 41.8 mg/kg bw/day for females at the 0.04 % dose level.
Conclusions:
No significant differences in carcinogenic effects was noted between treated and control groups.
Executive summary:

Male and female mice were exposed to the test substance in drinking water for 78 weeks at either 0.02 % or 0.04%. The calculated intake of test substance was 23 mg/kg bw/day for females and 19.8 mg/kg bw/day for males at the 0.02 % dose level and 41.8 mg/kg bw/day for females and 38.2 mg/kg bw/day for males at the 0.04 % dose level. No significant differences in carcinogenic effects was noted between treated and control groups. The NOAEL for males was 38.2 mg/kg bw/day and for females was 41.8 mg/kg bw/day.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
38.2 mg/kg bw/day

Additional information

Male and female mice were exposed to the test substance in drinking water for 78 weeks at either 0.02% or 0.04%. The calculated intake of test substance was 23 mg/kg bw/day for females and 19.8 mg/kg bw/day for males at the 0.02% dose level and 41.8 mg/kg bw/day for females and 38.2 mg/kg bw/day for males at the 0.04% dose level. No significant differences in carcinogenic effects was noted between treated and control groups. Based on this information, the NOAEL for carcinogenicity in males was 38.2 mg/kg bw/day and in females was 41.8 mg/kg bw/day.

Justification for classification or non-classification

Based on results of a repeated drinking water study, the substance does not need to be classified for carcinogenicity according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.