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Carcinogenicity

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Description of key information

In a drinking water study, male and female rats received 0, 2, 10, 50 mg hydrazine/l water over the whole period of life. With respect to body weight development, mortality or tumour development 2 mg hydrazine/l was tolerated without effects, 10 mg/l leads to reduced body weight development and 50 mg/l leads not to reduction of survival time but to a reduction in body weight gain of about 20 % . At this toxic dose male and female rats showed an increase in benign liver tumours and addionally, female rats an increase in maligne liver cell tumours (Steinhoff 1988). There is a longterm inhalation study on rats, mice, hamsters which is reported in brief. The used concentration for rats ranged between 0.05 and 5 ppm (0.066 -6.65 mg/m³) hydrazine, for mice between 0.05 and 1.0 ppm (0.066-1.33 mg/m³) and for hamsters between 0.25 and 5.0 ppm (0.33-6.65 mg/m³) The exposure period was 6 h per day, 5 days per week for 1 year (but not during holidays, not specified) followed by a lifelong post exposure observation period (MacEwen 1981, Vernot 1985).
Neoplastic lesions were observed
- in male and female rats from 1 ppm (1.33 mg/m³) onwards based on increase in benigne and maligne nasal tumours in male and females and thyroid carcinomas in males
- in female mice at 1 ppm (1.33 mg/m³) based on increase in lung adenoma development
- in male hamsters at 5 ppm(6.65 mg/m³) based on increase in benign nasal polyps
By comparison, the lowest concentration of 0.066 mg/m³ (0.05 ppm) is taken as a worst case LOAEC for local irritation.

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:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: no individual animal data shown
Reason / purpose for cross-reference:
reference to same study
Principles of method if other than guideline:
Oral application of different concentrations in drinking water over the entire lifespan, examination for effects.
GLP compliance:
not specified
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
animal age: 6 weeks,
housing : individually
room temperature: 23 °C
rel humidity: 70 %
diet ad libitum
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
they were prepared every second day
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
every 4 weeks a check was performed (further details not given)
Duration of treatment / exposure:
lifetime: until spontaneous death
Frequency of treatment:
daily ad libitum
Post exposure period:
no
Remarks:
Doses / Concentrations:
0, 2, 10, 50 mg/l
Basis:
other: calculated as hydrazine in water
No. of animals per sex per dose:
50
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: no
Positive control:
no
Observations and examinations performed and frequency:
body weight weekly, survival time, drinking water consumption of test animals
Sacrifice and pathology:
All animals were autopsied macrroscopic findings recorded:
Wet weight of brain, heartn lungs, liverm spleen, kidneys testes, adrenals, ovaries
histologicalexamination: adrenals, bladder , brain, epididymis, esophagus, eyes, femur, heart, intestines, kidneys, larynx, liver, lungs, mammary
gland, mesentery, nasopharynx, omentum, ovaries, pancreas, pituitary, prostate, salivary glands, seminal vesicles, skeletal muscels, skin, spinal cord with marrow, spleen, sternum, submaxillary gland with lymph nodes, testes, thymus if possiblem thyroid, tongue, trachea, uterus
Other examinations:
no data
Statistics:
yes, method not mentioned
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 examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
see section remarks on results
Dose descriptor:
other: Carcinogenicity
Effect level:
ca. 50 mg/L drinking water
Sex:
male/female
Basis for effect level:
other: based on occurrence of small, usually beningn liver cell tumours
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Dose descriptor:
NOAEL
Effect level:
ca. 2 mg/L drinking water
Remarks on result:
other: Effect type: toxicity (migrated information)

see also chapter 7.5.1 for toxicological results.


Carcinogenicity: There is an increase in the number of uterine tumours in female rats (highest concentration : 17/50(36 %) versus 8/50(16 %)in the controls and 117/326 = 36 % in the historical controls) Thus, these tumours give no indication of a carcinogenic effect of hydrazine liver cell tumours: 50 mg/l: significant increase in benign (males and
females) and malignant (only females) liver cell tumours No tumours were found in the control groups. Type of tumours 2 ppm-group (males): 1 hepatocellular adenoma and 1 haemangioma
10 ppm-group(males): 1 hepatocellular adenoma, 1 hepatocellular carcinoma, 1 cholangioma 50 ppm-group (males and females) 8 hepatocellular adenomas, 2 hepatocellular carcinomas, 1 cirrhotic carcinoma 3 cholangiomas (14.6% liver cell tumours [historical control range: 0-2.7%]) Number of rats with tumours conc: 2 - 10 - 50 versus concurrent(historical) control: benign liver tumours males: 1/49, 1/50, 4/49 versus 0/50 (4/326) females: 0/50, 0/50, 4/47 versus 0/50 (3/326) malign liver tumours males: 0/49, 1/50, 0/49 versus 0/50 (2/326) females: 0/50, 0/50, 3/47 versus 0/50 (0/326).

Executive summary:

In a drinking water study, male and female rats received 0, 2, 10, 50 mg hydrazine/l water over the whole period of life. With respect ot body weight development, mortality or tumour development 2 mg hydrazine/l was tolerated without effects, 10 mg/l leads to reduced body weight development and 50 mg/l leads not to reduction of survival time but to a reduction in body weight gain of about 20 % . At this toxic dose male and female rats showed an increase in benign liver tumours and addionally, female rats an increase in maligne liver cell tumours (Steinhoff 1988).

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEL
3 mg/kg bw/day
Study duration:
chronic
Species:
rat
Quality of whole database:
Although individual animal data are not shown this is the only reliable oral rat study providing sufficient information to be worth to be mentioned. In this publication of the drinking water study tumours are reported to occur only at the highest dose of 50 mg/l (ca 3 mg/kg bw/d) in a late phase of life time in the presence of marked toxicity. Based on this considerations and taking into account that oral application is not the predominant route of exposure against hydrazine this information will not be considered with respect to threshold evaluations.

Carcinogenicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: refers mostly to the guidelines of today
Reason / purpose for cross-reference:
reference to same study
Principles of method if other than guideline:
Other exposure of rat, mouse, hamster, dog for 1 year; see section any other information on material and methods.
GLP compliance:
not specified
Species:
other: rat, mouse, hamster, dog
Strain:
other: F344 rat; C57BL/6 mouse, Golden Syrian hamster, Beagle dogs
Sex:
male/female
Details on test animals or test system and environmental conditions:
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22
- Humidity (%): 50
Route of administration:
inhalation
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: air
Details on exposure:
inhalation exposures were conducted 6 hr/day, 5 days/week for 1 year without exposures on weekend and holidays
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Technico Autoanalyser proportioning pump and colorimeter
Duration of treatment / exposure:
12 months
Frequency of treatment:
6 h per day; 5 days per week; no exposures on holidays (no further data)
Post exposure period:
life time
Remarks:
Doses / Concentrations:
0, 0.05 - 5.0 ppm (0, 0.066-6.65 mg/m³)
Basis:

No. of animals per sex per dose:
100 male and 100 female rats/conc. 0.066, 0.33, 1.33, 6.65 mg/m³: post exposure observation: 18 months
400 female mice/conc.0.066, 0.33, 1.33 mg/m³; post exposure observation: 15 months
200 male hamsters/conc. 0.33, 1.33, 6.65 mg/m³ post exposure observation: 12 months
4 males and 4 female dogs/conc. 0.33. 1.33 mg/m³ post exposure observation: 38 months
Control animals:
yes, concurrent no treatment
Details on study design:
Post-exposure period: rats 18, mice 15, hamsters 12, dogs 38 months
Observations and examinations performed and frequency:
clinical signs of toxicology body weight development biweekly (10 mice/cage as cage groups),
hematology and clinical chemistry of dogs biweekly,
Sacrifice and pathology:
all animals that died or were killed during the study were necropsied: external examination and complete histopathological examination
Other examinations:
no further data
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 examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
see section remarks on results
Dose descriptor:
conc. level:
Effect level:
1 ppm
Sex:
male/female
Basis for effect level:
other: rat. increase in benigne and maligne nasal tumours in male and females, thyroid carcinomas in males
Remarks on result:
other:
Remarks:
Effect type: other: tumour development (migrated information)
Dose descriptor:
conc. level:
Effect level:
1 ppm
Sex:
female
Basis for effect level:
other: mouse: increase in lung adenoma development
Remarks on result:
other:
Remarks:
Effect type: other: tumour development (migrated information)
Dose descriptor:
conc. level:
Effect level:
5 ppm
Sex:
male
Basis for effect level:
other: hamster: increase in benign nasal polyps
Remarks on result:
other:
Remarks:
Effect type: other: tumour development (migrated information)
Dose descriptor:
conc. level:
Effect level:
0.25 ppm
Sex:
female
Basis for effect level:
other: dog: 1 hemangioma and 1 papillary carcinoma of the anus.
Remarks on result:
other:
Remarks:
Effect type: other: tumour development (migrated information)

Variance in exposure concentration mainly +/-10%; histopathology of rodents found dead or sacrified at termination of post exposure period (10% of surviving rats were nercopsied after 12 mo post exposure period) showed following tumor incidences different from controls:
hamsters: 0.25 - 1.0 - 5 ppm versus control benign nasal polyps 0/154 - 1/146 - 16/160 versus 1/181;

rats: 0.05 - 0.25 - 1.0 - 5.0 ppm versus control benign epithelial tumors of the nasal cavity

males: 2/99 - 2/99 - 10/98 - 66/99 versus 0/149

females: 1/99 - 0/100 - 4/97 - 31/98 versus 0/147

malignant tumors of the same type

males: 1/99 - 0/99 - 1/98 - 6/99 versus 0/149

females: 0/99 - 0/100 - 0/97 - 5/98 versus 0/147

thyroid adenocarcinomas

males: 6/99 - 5/99 - 9/98 - 13/99 versus 7/149

at 5 ppm 13/99 (male) versus 7/149;

mice: 0.05 - 0.25 - 1.0 ppm versus controls

pulmonary adenomas

females: 3/364 - 5/382 - 12/379 versus 4/373;
1 dog of the 0.25 ppm group showed 1 hemangioma and 1 papillary carcinoma of the anus.

Executive summary:

There is a longterm study on rats, mice, hamsters and dogs which is reported in brief. The used concentration for rats ranged between 0.05 and 5 ppm (0.066 -6.65 mg/m³) hydrazine, for mice between 0.05 and 1.0 ppm (0.066-1.33 mg/m³) and for hamsters between 0.25 and 5.0 ppm (0.33-6.65 mg/m³) The exposure period was 6 h per day, 5 days per week for 1 year (but not during holidays, not specified) followed by a lifelong post exposure observation period (MacEwen 1981, Vernot 1985).

Neoplastic lesions were observed

- in male and female rats from 1 ppm (1.33 mg/m³) onwards based on increase in benigne and maligne nasal tumours in male and females and thyroid carcinomas in males

- in female mice at 1 ppm (1.33 mg/m³) based on increase in lung adenoma development

- in male hamsters at 5 ppm(6.65 mg/m³) based on increase in benign nasal polyps

- in dogs at 0.025 ppm : 1 hemangioma and 1 papillary carcinoma of the anus evaluated as no consistent pathological effect..

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEC
0.066 mg/m³
Study duration:
chronic
Species:
rat
Quality of whole database:
This is a reliable long term study using the most appropriate route of exposure and is therefore evaluated with Klimisch Score 2.

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Under Regulation No. 1272/2008 (GHS) the substance is classified in Carcinogenicity Class 1B; Hazard Statement H350: May cause cancer.

Additional information

Oral route

In the long-term drinking water study in rats under this particular severe experimental condition of exposure during the total lifetime, hydrazine induced increased liver tumours, at the highest the toxic - concentration of about 3 mg/kg bw/day (no effect at the next lower dose of 0.7 mg/kg bw/day). The majority of the liver tumours were benign thus demonstrating that hydrazine showed only a weak carcinogenic effect (Steinhoff 1988). In contrast, the 2 year drinking water study in mice revealed no increase in tumour incidence up to the highest dose tested (Steinhoff et al. 1990).

There are several publications discussing the mechanism of action of hydrazine in rat and mouse suggesting a dose-dependent increase in liver DNA methylation after single and repeated oral administration. In this context it is discussed that treatment with hydrazine disturb the balance of methylation and demethylation on N-7 and O-6 of guanine by inhibiting the demethylation which would result in accumulation of the methylated purines in the liver DNA (see also DFG 1989). Dose-response studies in rats revealed a single oral dose of 0.1 mg/kg as a starting dose for effects on liver DNA methylation (borderline effect, clear effects with 10 mg/kg; van Delft 1997; clear effect at 30 mg/kg; Becker et al. 1981). After the third of four oral doses of 3 mg/kg increase of 7-methylguanine was observed as trace and readily detectable after 4 treatments (Becker et al. 1981). Evidence of liver toxicity was shown at 2.5 mg/kg (exposure for 1-10 days; decrease of GSH, increase of triglycerides; Jenner & Timbrell 1992) and 3 mg/kg (3-4 doses; Becker et al. 1981). Therefore it is plausible that the liver tumours after long-term high dose exposure are secondary to liver toxicity and alteration of the balance of methylation and demethylation.

Inhalation route

In the above described inhalation study the local irritant, hydrazine, induced in hamsters and in rats, but not in mice, tumours only of the epithelium of the nasal cavity starting at 1.3 mg/m³. In contrast, the LOAEC in rats based on irritational effects in the nose, the larynx and trachea was much lower (0.066 mg/m³).As it is known that this tissue is highly sensitive to the local effects of carcinogens in rodents, it is difficult to extrapolate the results of this study to the human situation. It seems to provide evidence for a low carcinogenic potential of hydrazine (DFG 1989)

Dermal route

There are no data available using the dermal route

Human information

There are epidemiological studies available investigating the association between hydrazine exposure and tumour development.(Cordier 1993, Ritz 1996). Although they are of limited validity (small numbers of participants, only estimated exposure information and the lack of discussion of confounding factors they did not reveal an indication of a causal association between human exposure to hydrazine and the development of cancer. Recently, Ritz (2006) published the results of an additional epidemiological study on the association between hydrazine exposure and lung cancer mortality in aerospace workers. Whereas this study of aerospace workers give some evidence of an association between hydrazine exposure and lung cancer mortality, a variety of limitations mentioned in the paper limits the overall evaluation and relevance for the assessment of hydrazine: at first, Ritz defined as "Hydrazine" a mixture of hydrazine, 1-methylhydrazine and 1,1 -dimethylhydrazine of unknown ratio. Most importantly, however, the exposure assessment is based on a job-exposure matrix adjusted for other carcinogens e.g trichloroethylene but without specific measurements and potential confounding factors as e.g. smoking could only be partly included in the assessment. In the same cohort an association between mineral oil exposure and eg lung cancer risk was reported (Zhao et al (2005), Am J Indust Med 48, 249 -258). In contrast to this publication, in the meantime, data are available from the hydrazine producing industry (Arkema 2003) that show that under the circumstances of hydrazine production a limited epidemiological study do not reveal an indication of a carcinogenic response in humans under historic working conditons. These data are confirmed in a very recent follow-up study (Arkema 2014) which covers a longer follow-up period than the 2003 study and involves the integration of new workers into the cohort: no evidence of relationship between hydrazine exposure and cancer is observed.

Conclusion

Hydrazine is classified as animal carcinogen. Irrespective of this classification, the database is not fully conclusive regarding the mode of action that leads to the tumour response in animal studies, e.g. the carcinogenic effects of hydrazine have been shown only with maximally tolerated unambiguously toxic doses or locally irritating concentrations. Tumour responses are limited to the first site of contact in inhalation studies (nasal cavity) or the first organ of systemic availability after oral dosing (liver), respectively. Studies on the mode of action led to the conclusion that for the oral intake it is plausible that the liver tumours after long-term high dose exposure are secondary to liver toxicity and alteration of the balance of DNA methylation and demethylation. Regarding the local effects after inhalation exposure from the dose-response assessment (irritation threshold much lower than the concentration leading to tumours) it can be derived that that a direct cytotoxic mechanisms is most probably dominant.

Genotoxicity seems not to be a major cause for the tumour responses as for primary genotoxic carcinogens multiorgan tumour responses with a wide tissue distribution is typical, instead of a local first site of contact/first organ of systemic availability. Therefore, even if some role of genotoxicity at very high doses cannot be excluded, based on the available data the overall weight of evidence points to a non-genotoxic mechanism for the tumour responses in animal experiments. Local toxicity is regarded to be of main importance with tumour development as secondary response

That reflection of the database led industry initially to propose to strengthen the database with a testing proposal to examine the irritation threshold after repeated inhalation with the aim to define the most sensitive level of the respiratory tract after repeated exposure, as well as the threshold for irritation after repeated exposure and on the respective dose-response relationship.

Based on responses received from the Competent Authorities that proposal was revised taking into consideration the following aspects:

• Within the activity of the EU Commission for an amendment of Directive 2004/37/EC on carcinogens and mutagens the proposal to set the 8hr TWA for Hydrazine (0.013 mg/m3) as a Binding Limit Value was agreed by the Advisory Committee on Safety and Health at Work (Opinion Doc. 2011/12).

• After implementation such a Binding Limit Value will be the corner stone for the risk management and it is expected that a more in depth knowledge on the Mode of Action most probably will not influence that Binding Limit Value.

• This view was supported by the responses from Member States to the testing proposal

• The scientific and regulatory value for further toxicological testing needs to be weighted with animal welfare considerations.

Based on these considerations the testing proposal for a short-term repeated dose toxicity study via the inhalation route was deleted.”


Justification for selection of carcinogenicity via oral route endpoint:
Although individual animal data are not shown this is the only reliable study providing sufficient information to be worth to be mentioned

Justification for selection of carcinogenicity via inhalation route endpoint:
This is a reliable long term study using the most appropriate route of exposure and is therefore evaluated with Klimisch Score 2

Carcinogenicity: via inhalation route (target organ): respiratory: nose