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Toxicological information

Carcinogenicity

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Description of key information

There is sufficient information available to make an assessment of the likely carcinogenic potential of acetylene.  The data available via the inhalation route reports acetylene to be non-carcinogenic in rats and mice.  No link between the use of acetylene and cancer has been established after many years of use, in particular as an anaesthetic.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no study available

Carcinogenicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
carcinogenicity: inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non GLP, non-guideline animal study, some limitations regarding the test method but adequate for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
Control animals exposed nose only to 20 ppm acetylene for 18 months (6 hr/day, 2 days/wk)
GLP compliance:
not specified
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 6-7 week old
- Housing: individually during non-exposure periods
- Diet: Altro-min ad libitum
- Water: Tap water ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature: 22-24°C
- Humidity: 45± 5%
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: No data
Route of administration:
inhalation
Type of inhalation exposure (if applicable):
nose only
Vehicle:
other: air
Details on exposure:
EXPOSURE
- Nose only exposure, noses in contact with the exposure mixture which was streamed with a flow rate of 5 L/min from the bottom to the top of the exposure chamber (300 x 240 x 35 mm)
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The concentration of DCA was monitored, acetylene acted as control in this study
Duration of treatment / exposure:
18 months
Frequency of treatment:
Daily (6 h/day, 2 days/wk)
Post exposure period:
Natural life span
Remarks:
Doses / Concentrations:
20 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
21.4 mg/m3
Basis:
nominal conc.
No. of animals per sex per dose:
30
Control animals:
yes
Details on study design:
- Treated animals were exposed nose only to 14 ppm dichloroacetylene (DCA).
- The effective exposure mixture consisted of DCA, nitrogen, acetylene (as a stabiliser, maximum 20 ppm) and air.
- Control animals were kept and exposed under identical conditions but without DCA in the exposure mixture.
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: animals were checked twice daily for signs of toxicity and mortality

BODY WEIGHT: Yes
- Time schedule: at weekly intervals

URINALYSIS: Yes
- Time schedule: urinalyses for protein and glucose were carried out monthly
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- Pathological examination: all deceased animals were given a complete gross pathological examination, although delay between death and the post mortem examination must have lead to some autolytic changes.

HISTOPATHOLOGY: Yes
- Histological examination was limited to liver, spleen, kidney, lung, heart, brain, stomach, genital tract and tissues with "macroscopically visible modifications"
- The upper respiratory tract (nose, larynx and trachea) was not examined
- Endocrine glands (adrenals, thyroids, parathyroids, pituitary), pancreas, small and large intestines and urinary bladder were not examined
Statistics:
According to Kaplan Meier, Cox, Maniel and Cochran. The probability calculus of tumours was performed according to Saffiotti et and Cox.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Dose descriptor:
NOAEC
Effect level:
20 ppm
Sex:
male/female
Basis for effect level:
other: 21.4 mg/m3. No effect on survival and no obvious changes in tumour profile from that to be expected in aged rats
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Conclusions:
The study proved capable of detecting a potent carcinogenic effect of DCA. Exposure of acetylene to rats in the control groups, up to a nominal maximum concentration of 20 ppm, under the same regime as the test groups had no effect on survival and no obvious changes in tumour profile from that to be expected in aged rats.

20 ppm (21 mg/m3 equivalent) can be considered a NOAEC.
Executive summary:

The study exposed a group of 30 rats to acetylene daily (6 hr/day, 2 days/wk) for 18 months, these animals served as a control group to test animals that received DCA (dichloroacetylene). The study proved capable of detecting a potent carcinogenic effect of DCA. Exposure of acetylene to rats in the control groups, up to a nominal maximum concentration of 20 ppm, under the same regime as the test groups had no effect on survival and no obvious changes in tumour profile from that to be expected in aged rats.

Within the conditions of the study 20 ppm (21.4 mg/m3 equivalent) can be considered a NOAEC.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
21.4 mg/m³

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

There are no standard lifetime animal studies available on acetylene in order to directly investigate for possible carcinogenic activity. However, there is sufficient information available to make an assessment of the likely carcinogenic potential of the material.

Testing data relevant for carcinogenicity

In vitro data 

Acetylene has been examined for mutagenicity in vitro in a range of recognised core assay types, examining for endpoints of gene mutation, chromosomal damage and chromosomal numerical changes. It has shown negative results in all assays. It is concluded that the available data indicate that acetylene has no significant genotoxicity.

Animal data

Reichert et al (1984) exposed a group of 30 rats or mice to acetylene daily (6 h/day, 2 days/wk) for 12 or 18 months, these animals served as a control group to test animals that received DCA (dichloroacetylene). The study proved capable of detecting a potent carcinogenic effect of DCA. Exposure of acetylene to animals in the control groups, up to a nominal maximum concentration of 20 ppm, under the same regime as the test groups had no effect on survival and no obvious changes in tumour profile from that to be expected in aged rats/mice. Within the conditions of the study 20 ppm (21.4 mg/m3 equivalent) can be considered a NOAEC.

 

Human data

The ACC Acetylene Panel (2006) reviewed the available human data for acetylene. Acetylene has been used for over 100 years as an anesthetic and industrial chemical, and few complications of using this gas have been reported, published epidemiological studies have failed to establish a link between use of acetylene and cancer (see endpoint summary for further details). Waxweiler, 1981 found no evidence of any association with liver angiosarcoma in workers exposed to a number of materials. Acetylene exposure was not a risk factor in mortality from lung cancer in a case-referent study in which exposure to chemicals in an acetylene and phthalic anhydride plant accounted for one third of the total number of lung cancer deaths (Riboli et al., 1988). A pilot study on 454 men found no association between occupational exposure to acetylene and the development of cancer (Siemiatycki et al., 1982). A study of 370 workers involved in acetylene cylinder manufacture between 1935 -1975, reported excess mortality from lung cancer, and cancer of the stomach and pancreas. However, no association between exposure to acetylene and lung cancer was identified (Newhouse et al., 1988). Acetylene also was not listed as a risk factor for developing cancer in a study of 632 Danish male molders (Hansen, 1991). In two case-controlled studies, acetylene exposure was not identified as a risk factor for developing multiple myeloma (Morris et al., 1986; Williams et al., 1989). In 1980 Rohm and Haas reported the findings of aTexasplant, which utilizes acetylene and other chemicals to produce acrylate and methacrylate ester, the excess of total cancer deaths in those hired from 1958 to 1962, could not be correlated with job-related causes.

Justification for classification or non-classification

The available data indicates that acetylene does not warrant classification under CLP.