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EC number: 200-848-3 | CAS number: 75-20-7
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Endpoint summary
Administrative data
Description of key information
The risk assessment of calcium carbide is driven by local effects to the lung (respiratory irritation). Thus, data on respiratory irritation is provided and complemented by information on systemic toxicity of calcium (oral route) and acetylene (inhalation route, IUCLID section 7.5.2 and 7.7).
A short-term repeated dose toxicity study with the substance as such was disregarded due to major deficiencies in methodology and documentation.
Key value for chemical safety assessment
Repeated dose toxicity: via oral route - systemic effects
Link to relevant study records
- Endpoint:
- sub-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:
- As calcium carbide instantly hydrolyses to Ca(OH)2 and C2H2 upon contact with water/moisture the assessment is based on the degradation products. For details please refer to the read across report in section 13.
- Reason / purpose for cross-reference:
- read-across source
- Analytical verification of doses or concentrations:
- no
- Frequency of treatment:
- daily ad libitum
- Positive control:
- No
- Clinical signs:
- no effects observed
- Mortality:
- no mortality observed
- Body weight and weight changes:
- no effects observed
- Haematological findings:
- effects observed, treatment-related
- Clinical biochemistry findings:
- effects observed, treatment-related
- Urinalysis findings:
- effects observed, treatment-related
- 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:
- no effects observed
- Details on results:
- No mortality occured in all experiments.
Exp I: body wights decreased in the high dose, still within the 10% of the control group. Minor changes in some hematological and biochemical parameters, suggesting nephrotoxicity and hepatotoxicity at the high dose group; however, not accopmpanied by histological findings. Only histopathological finding relevant to treatment in the high dose group was some mild effects: localized erosion, necrosis and atrophy in the mucosa of the grandular stomach.
Exp II: Body weights significantly reduced in the 30% group. Histological examination showed nephrocalcinosis in all groups, including the control.
Exp III: nephrocalcinosis detected only in the group fed with the synthetic diet B. - Key result
- Dose descriptor:
- NOAEL
- Effect level:
- 1 840 mg/kg bw/day (nominal)
- Based on:
- act. ingr.
- Sex:
- female
- Basis for effect level:
- other: overall effects; no severe toxicological findings detected.
- Key result
- Critical effects observed:
- not specified
- Conclusions:
- 5% calcium lactate in drinking water resulted in minor toxicological findings, such as minor changes in some hematological and biochemical parameters, and minor decreases in body weights. No severe toxicological findings were seen in the histopathological examination. The NOAEL can be set at 5%, i.e. 1840 mg/kg bw.
- Executive summary:
The subchronic toxicity of calcium lactate was studied using F344 rats. In Experiment I, calcium lactate was mixed at 5, 2.5, 1.25, 0.6, and 0.3% in the drinking water and the rats were given this solution ad libitum for 13 weeks. As a result, the inhibition of body weight gain in the 5% group fell within 10% of that in the control group. Some examination values showed variations in the hematological and hematobiochemical studies, but no controversial findings were obtained in the pathohistological search. Since the highest solubility of calcium lactate is 5%, Experiments II and III were carried out by giving blended diet in order to study the toxicity at higher doses. In Experiment II, calcium lactate was mixed at concentrations of 30, 20, 10, and 5% in the B-blend powder diet and then the rats were given this diet ad libitum for 20 weeks. In Experiment III, the rats were given the CRF-1 or the B-blend powder diet ad libitum for 8 weeks. As a result, in Experiment II, nephrocalcinosis was observed in all the groups including the control group. The degree of the lesion was in reverse correlation with the administered concentrations of calcium and the lesion was seen more intensely in female rats. In Experiment III, nephrocalcinosis resulting from the administration of the B-blend diet was already observed in the 4th week. Nephrocalcinosis as observed in Experiments II and III was attributable to the small Ca/P value in the B-blend diet and not related to the calcium content per se in the diet. The NOAEL is set at 1840 mg/kg bw.
This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the read-across report attached to IUCLID section 13.
- Endpoint:
- short-term repeated dose toxicity: oral
- Data waiving:
- study scientifically not necessary / other information available
- Justification for data waiving:
- a short-term toxicity study does not need to be conducted because a reliable sub-chronic (90 days) or chronic toxicity study is available, conducted with an appropriate species, dosage, solvent and route of administration
- other:
- Critical effects observed:
- not specified
- Endpoint:
- short-term repeated dose toxicity: oral
- Type of information:
- experimental study
- Adequacy of study:
- disregarded due to major methodological deficiencies
- Study period:
- 2019
- Reliability:
- 3 (not reliable)
- Rationale for reliability incl. deficiencies:
- significant methodological deficiencies
- Justification for type of information:
- The present study shows major deficiencies in method and documentation. First of all, the report does not state sufficient details for gavage administration, including vehicle and the form, in which calcium acetylide was applied. In case of calcium acetylide, this however is important as the substance reacts violently with water to generate gaseous acetylene and calcium hydroxide, thereby leading to a local depletion of water. The reaction is exothermic and can locally create excess heat, which can potentially lead to local burns and tissue damage. Second, the test material specifications regarding the purity of the applied calcium acetylide and the content of potential impurities, was not specified. It is mentioned in the report that calcium acetylide often contains impurities including arsenic and phosphorous, which themselves can exert toxic effects potentially covering those of the test substance.
The study conception is furthermore not compliant to the relevant OECD TG 407 guideline for a short-term repeated dose toxicity study. Several shortcomings include the use of only one sex (males), a lower number of total animals (6 instead of 10 animals per dose), and the use of two instead of three dose groups. This impairs a robust assessment of dose-dependency of effects. In addition, there was no justification for the selection of dose levels.
Furthermore, a detailed list of findings for individual animals was not reported. Significant histopathological findings were only reported in the high dose group of calcium acetylide treatment and included desquamation of the lining epithelium of the stomach, necrosis of villi and different degrees of mucosal degeneration in the small intestine. These signs indicate that local effects could be involved in the observed signs of toxicity.
Evaluation of the inherent quality of the provided data with the ECVAM ToxRTool resulted in the assignment of Klimisch category 3. Consequently, and especially in the light of the missing details on oral administration of calcium acetylide, the study design and reporting do not allow a thorough evaluation of the observed effects. - Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)
- Deviations:
- yes
- Remarks:
- 6 animals / group, 2 test groups
- GLP compliance:
- not specified
- Remarks:
- based on the published data the registrant cannot decide whether or not the study has been conducted under GLP conditions
- Limit test:
- no
- Species:
- rat
- Strain:
- Wistar
- Sex:
- male
- Route of administration:
- oral: gavage
- Vehicle:
- not specified
- Analytical verification of doses or concentrations:
- not specified
- Duration of treatment / exposure:
- 30 days
- Frequency of treatment:
- once per day
- Dose / conc.:
- 50 mg/kg bw/day (nominal)
- Dose / conc.:
- 100 mg/kg bw/day (nominal)
- No. of animals per sex per dose:
- 6
- Control animals:
- yes, concurrent no treatment
- Positive control:
- no
- Observations and examinations performed and frequency:
- body weight examined weekly
- Sacrifice and pathology:
- At the end of the experiment, the animals were euthanized using standard procedure.The organs were excised, and blood was collected in EDTA tubes. Serum was used for biochemical analysis. The organosomatic index (relative organ weight) was also calculated.
- Statistics:
- one-way analysis of variance (ANOVA) followed by the Dunnett multiple comparison test using GraphPad Prism 7.0. p < 0.05
- Mortality:
- no mortality observed
- Body weight and weight changes:
- no effects observed
- Description (incidence and severity):
- The administration of CaC2 for 30 days produced mild changes in body weight and food and water consumption compared with the normal rats.
- Food consumption and compound intake (if feeding study):
- no effects observed
- Description (incidence and severity):
- The administration of CaC2 for 30 days produced mild changes in body weight and food and water consumption compared with the normal rats.
- Food efficiency:
- not examined
- Water consumption and compound intake (if drinking water study):
- not specified
- Ophthalmological findings:
- not specified
- Description (incidence and severity):
- Group Hb, g/dL RBC, Platelet Total WBC Neutrophil Lymphocyte Eosinophil
millions/cu count, count,
mm 105/cu mm cells/cu
mm
Normal 14.36 ± 0.68 5.56 ± 0.22 2.86 ± 0.39 4116.66 ± 354.49 31.16 ± 5.91 65.83 ± 5.63 3 ± 0.63
CaC2, 100 14.2 ± 0.57 5.55 ± 0.21 3.03 ± 0.32 5900 ± 25.33 ± 71.83 ± 2.83 ± 0.75
mg/kg 732.12 04. Mrz Mrz 48
CaC2, 50 13.98 ± 5.48 ± 0.11 3.88 ± 0.48 4708.33 ± 26.83 ± 69.83 ± 3.333 ±
mg/kg 0.23 420.02 Mai 19 Mai 34 01. Mrz - Organ weight findings including organ / body weight ratios:
- effects observed, treatment-related
- Description (incidence and severity):
- Organosomatic Normal CaC2, 100 mg/kg CaC2, 50 mg/kg
index
Brain 0.651 ± 0.083 0.518 ± 0.098 0.609 ± 0.057
Lung 0.630 ± 0.149 0.559 ± 0.096 0.525 ± 0.159
Liver 2.576 ± 0.151 2.738 ± 0.197 2.542 ± 0.160
Pancreas 0.151 ± 0.026 0.127 ± 0.022 0.141 ± 0.020
Spleen 0.275 ± 0.058 0.285 ± 0.038 0.311 ± 0.065
Kidney 0.584 ± 0.060 0.636 ± 0.060 0.574 ± 0.071 - Histopathological findings: non-neoplastic:
- effects observed, treatment-related
- Description (incidence and severity):
- Histological observations of various organs like liver, kidney, lungs, and small intestine (duodenum, jejunum,
and ileum) showed toxic changes at high doses of CaC2. CaC2-treated liver displayed dilated
central vein, congested sinusoids, and microvesicular fatty change with vacuolated large hepatocytes. Macroscopically,
there was a pale hard mass on the posterior surface of the liver.
Histopathological analysis of lungs showed dense lymphocyte infiltration at high doses of
CaC2. Stomach histology showed desquamating lining epithelium, increase in mucous gland in the
lamina propria by the treatment of CaC2 at the high doses. Histological observations of small intestine
showed necrosis of villi in all treated groups, by using an intestinal mucosal lesion
scoring system (0–4). Regular morphology was represented as 0, subepithelial congestion with slight cellular
desquamation at the villi tips as score 1, mucosal congestion with loss of less than half of the villi as score 2, loss
of more than half of the villi as score 3, and submucosal degeneration as score 4. According to
intestinal mucosal lesion scoring, extremely significant injuries were observed in all the treated groups except
low-dose (50 mg/kg) CaC2-treated animals. Neither morphological nor structural changes were observed in
various organs like heart, brain, pancreas, spleen, etc. - Key result
- Dose descriptor:
- NOEL
- Effect level:
- 50 mg/kg bw/day (nominal)
- Based on:
- test mat.
- Sex:
- male
- Basis for effect level:
- histopathology: non-neoplastic
- Key result
- Critical effects observed:
- yes
- Lowest effective dose / conc.:
- 100 mg/kg bw/day (nominal)
- System:
- gastrointestinal tract
- Organ:
- not specified
- Treatment related:
- yes
- Dose response relationship:
- yes
- Relevant for humans:
- yes
- Conclusions:
- Industrial-grade CaC2 showed at lower doses mild to moderate toxicity to the internal organs of rats and a decline in hemoglobin level. The elevated platelet, WBC count, and lymphocyte infiltration in the tissues indicate inflammatory responses. The study revealed that CaC2 are toxic to organs and might weaken the immune system.
However, the study was disregarded due to major deficiencies in study design and documentation. - Executive summary:
In a subacute toxicity study performed according to OECD 407, CaC2 was administered to 6 male Wistar rats/dose by oral gavage at dose levels of 50 and 100 mg/kg bw/day for 30 days. At subacute doses, RBC and hemoglobin levels were found to be declined (p< 0.01), whereas total WBC and platelet counts, especially lymphocytes, were elevated remarkably (p < 0.01). Total protein, albumin, and urea were also found to be increased (p< 0.01). Histopathological observations support the toxicity in rats at higher doses (100 mg/kg bw/day) of CaC2. The study revealed that CaC2 cause toxic effects on the internal organs of rats. The subsequent inflammatory response might have weakened the immune system. Based on the results of this study, the NOAEL is considered to be 50 mg/kg bw/day.
The study was disregarded due to major deficiencies in method and documentation. First of all, the report does not state sufficient details for gavage administration, including vehicle and the form, in which calcium acetylide was applied. In case of calcium acetylide, this however is important as the substance reacts violently with water to generate gaseous acetylene and calcium hydroxide, thereby leading to a local depletion of water. The reaction is exothermic and can locally create excess heat, which can potentially lead to local burns and tissue damage. Second, the test material specifications regarding the purity of the applied calcium acetylide and the content of potential impurities, was not specified. It is mentioned in the report that calcium acetylide often contains impurities including arsenic and phosphorous, which themselves can exert toxic effects potentially covering those of the test substance.
The study conception is furthermore not compliant to the relevant OECD TG 407 guideline for a short-term repeated dose toxicity study. Several shortcomings include the use of only one sex (males), a lower number of total animals (6 instead of 10 animals per dose), and the use of two instead of three dose groups. This impairs a robust assessment of dose-dependency of effects. In addition, there was no justification for the selection of dose levels.
Furthermore, a detailed list of findings for individual animals was not reported. Significant histopathological findings were only reported in the high dose group of calcium acetylide treatment and included desquamation of the lining epithelium of the stomach, necrosis of villi and different degrees of mucosal degeneration in the small intestine. These signs indicate that local effects could be involved in the observed signs of toxicity.
Consequently, and especially in the light of the missing details on oral administration of calcium acetylide, the study design and reporting do not allow a thorough evaluation of the observed effects concerning the involvement of systemic or local non-specific mode of actions of the substance.
Based on the deficiencies described, evaluation of the inherent quality of the provided data with the ECVAM ToxRTool resulted in the assignment of Klimisch category 3 and thus the study was not regarded suitable for the assessment of repeated dose toxicity of the test substance calcium acetylide.
Referenceopen allclose all
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed
Repeated dose toxicity: inhalation - systemic effects
Link to relevant study records
- Endpoint:
- sub-chronic toxicity: inhalation
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Justification for type of information:
- As calcium carbide instantly hydrolyses to Ca(OH)2 and C2H2 upon contact with water/moisture the assessment is based on the degradation products. For details please refer to the read across report in section 13.
- Reason / purpose for cross-reference:
- read-across source
- Clinical signs:
- no effects observed
- Mortality:
- no mortality observed
- Body weight and weight changes:
- no effects observed
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Gross pathological findings:
- no effects observed
- Key result
- Dose descriptor:
- NOAEC
- Effect level:
- 250 000 ppm
- Based on:
- test mat.
- Sex:
- not specified
- Basis for effect level:
- gross pathology
- Remarks on result:
- not determinable
- Remarks:
- no NOAEC identified
- Key result
- Critical effects observed:
- not specified
- Conclusions:
- Repeated exposure of rats to a concentration of 25% acetylene (1h/day for up to 93 days) did not cause any organ toxicity.
- Executive summary:
In a non-guideline subchronic inhalation toxicity study, acetylene was administered to 2 -47 rats/sex/concentration by whole body exposure at concentrations of 0 and 25,000 ppm daily for 1 hour for up to 93 days.
In treated animals that survived to termination, no evidence of cellular injury to the parenchymatous cells of the heart, lungs, liver, kidneys, or spleen was reported. However, capillary hyperemia of the liver, kidneys and spleen was observed in some rats exposed to 25%. This effect was observed until at least the second day after the last exposure to the gas but was not evident in animals killed later (up to 5 days after the last exposure). Since capillary hyperemia was not observed in rats exposed to higher concentrations of acetylene, it does not appear to be test-material related.
Based on the results of this study, the NOAEC is considered to be 25,000 ppm.
This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the read-across report attached to IUCLID section 13.
- Endpoint:
- short-term repeated dose toxicity: inhalation
- Data waiving:
- study scientifically not necessary / other information available
- Justification for data waiving:
- a short-term toxicity study does not need to be conducted because a reliable sub-chronic (90 days) or chronic toxicity study is available, conducted with an appropriate species, dosage, solvent and route of administration
Referenceopen allclose all
In treated animals that survived to termination, no evidence of cellular injury to the parenchymatous cells of the heart, lungs, liver, kidneys, or spleen was reported. However, capillary hyperemia of the liver, kidneys and spleen was observed in some rats exposed to 25%. This effect was observed until at least the second day after the last exposure to the gas but was not evident in animals killed later (up to 5 days after the last exposure). Since capillary hyperemia was not observed in rats exposed to higher concentrations of acetylene, it does not appear to be test-material related.
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed
Repeated dose toxicity: inhalation - local effects
Link to relevant study records
- Endpoint:
- sub-chronic toxicity: inhalation
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Justification for type of information:
- As calcium carbide instantly hydrolyses to Ca(OH)2 and C2H2 upon contact with water/moisture the assessment is based on the degradation products. For details please refer to the read across report in section 13.
- Reason / purpose for cross-reference:
- read-across source
- Clinical signs:
- no effects observed
- Mortality:
- no mortality observed
- Body weight and weight changes:
- no effects observed
- Organ weight findings including organ / body weight ratios:
- no effects observed
- Gross pathological findings:
- no effects observed
- Key result
- Dose descriptor:
- NOAEC
- Effect level:
- 250 000 ppm
- Based on:
- test mat.
- Sex:
- not specified
- Basis for effect level:
- gross pathology
- Remarks on result:
- not determinable
- Remarks:
- no NOAEC identified
- Key result
- Critical effects observed:
- not specified
- Conclusions:
- Repeated exposure of rats to a concentration of 25% acetylene (1h/day for up to 93 days) did not cause any organ toxicity.
- Executive summary:
In a non-guideline subchronic inhalation toxicity study, acetylene was administered to 2 -47 rats/sex/concentration by whole body exposure at concentrations of 0 and 25,000 ppm daily for 1 hour for up to 93 days.
In treated animals that survived to termination, no evidence of cellular injury to the parenchymatous cells of the heart, lungs, liver, kidneys, or spleen was reported. However, capillary hyperemia of the liver, kidneys and spleen was observed in some rats exposed to 25%. This effect was observed until at least the second day after the last exposure to the gas but was not evident in animals killed later (up to 5 days after the last exposure). Since capillary hyperemia was not observed in rats exposed to higher concentrations of acetylene, it does not appear to be test-material related.
Based on the results of this study, the NOAEC is considered to be 25,000 ppm.
This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the read-across report attached to IUCLID section 13.
- Endpoint:
- short-term repeated dose toxicity: inhalation
- Data waiving:
- study scientifically not necessary / other information available
- Justification for data waiving:
- a short-term toxicity study does not need to be conducted because a reliable sub-chronic (90 days) or chronic toxicity study is available, conducted with an appropriate species, dosage, solvent and route of administration
Referenceopen allclose all
In treated animals that survived to termination, no evidence of cellular injury to the parenchymatous cells of the heart, lungs, liver, kidneys, or spleen was reported. However, capillary hyperemia of the liver, kidneys and spleen was observed in some rats exposed to 25%. This effect was observed until at least the second day after the last exposure to the gas but was not evident in animals killed later (up to 5 days after the last exposure). Since capillary hyperemia was not observed in rats exposed to higher concentrations of acetylene, it does not appear to be test-material related.
Endpoint conclusion
- Endpoint conclusion:
- adverse effect observed
- Dose descriptor:
- LOAEC
- 5 mg/m³
- Study duration:
- subacute
- Species:
- other: human volunteers and workers
- Quality of whole database:
- For Study see section 7.10.3
Respiratory irritation of calcium oxide/hydroxide has been assessed in several studies in volunteers and in occupational settings. The information is considered relevant for the risk assessment of calcium carbide.
Repeated dose toxicity: dermal - systemic effects
Link to relevant study records
- Endpoint:
- sub-chronic toxicity: dermal
- Data waiving:
- other justification
- Justification for data waiving:
- other:
- Endpoint:
- short-term repeated dose toxicity: dermal
- Data waiving:
- other justification
- Justification for data waiving:
- other:
- Critical effects observed:
- not specified
Referenceopen allclose all
Endpoint conclusion
- Endpoint conclusion:
- no study available
- Quality of whole database:
- no study available but no further data necessary
Repeated dose toxicity: dermal - local effects
Link to relevant study records
- Endpoint:
- sub-chronic toxicity: dermal
- Data waiving:
- other justification
- Justification for data waiving:
- other:
- Endpoint:
- short-term repeated dose toxicity: dermal
- Data waiving:
- other justification
- Justification for data waiving:
- other:
- Critical effects observed:
- not specified
Referenceopen allclose all
Endpoint conclusion
- Endpoint conclusion:
- no study available
- Quality of whole database:
- no study available but no further data necessary
Additional information
In aqueous solution, calcium carbide rapidly decomposes into calcium hydroxide and acetylene (see endpoint summary on hydrolysis of CaC2). Local effects are related to calcium hydroxide, which liberates OH- ions, affecting the skin and the mucous membranes. Systemic effects would be related to calcium ions. Acetylene is released as a gas. It has a long history of use as a general anaesthetic and is considered to be of very low toxicity (disregarding the "narcotic" effects).
The risk assessment of calcium carbide is driven by local effects to the lung (respiratory irritation, STOT SE 3). Respiratory irritation of calcium oxide/hydroxide has been assessed in several studies in volunteers and in occupational settings (see section 7.9.3). This information is considered relevant for the risk assessment of calcium carbide.
Any systemic effects of CaC2 are considered to be negligible at normal occupational exposures. The calcium fraction in CaC2 is 63 %. Assuming an exposure level of 1-5 mg/m³ and an air volume of 10 m³ inhaled during an 8-hour workday, this results in an inhaled dose of 6.3-31,5 mg calcium per day. Thus, occupational exposures makes a negligible contribution to the daily systemic calcium uptake as the Tolerable Upper Intake Level for calcium is 2500 mg/day (EFSA Journal 2012;10(7): 2814), and daily intake of calcium from the diet is estimated at 683-753 mg/day (Scientific Committe on Food (SCF, 2003) SCF/CS/NUT/UPPLEV/64. 23 April 2003).
In a subacute toxicity study performed according to OECD 407, CaC2 was administered to 6 male Wistar rats/dose by oral gavage at dose levels of 50 and 100 mg/kg bw/day for 30 days (Bini et al 2019). At subacute doses, RBC and hemoglobin levels were found to be declined (p< 0.01), whereas total WBC and platelet counts, especially lymphocytes, were elevated remarkably (p < 0.01). Total protein, albumin, and urea were also found to be increased (p< 0.01). Histopathological observations support the toxicity in rats at higher doses (100 mg/kg bw/day) of CaC2. The study revealed that CaC2 cause toxic effects on the internal organs of rats. The subsequent inflammatory response might have weakened the immune system. Based on the results of this study, the NOAEL is considered to be 50 mg/kg bw/day. The study was disregarded due to major deficiencies in method and documentation. First of all, the report does not state sufficient details for gavage administration, including vehicle and the form, in which calcium acetylide was applied. In case of calcium acetylide, this however is important as the substance reacts violently with water to generate gaseous acetylene and calcium hydroxide, thereby leading to a local depletion of water. The reaction is exothermic and can locally create excess heat, which can potentially lead to local burns and tissue damage. Second, the test material specifications regarding the purity of the applied calcium acetylide and the content of potential impurities, was not specified. It is mentioned in the report that calcium acetylide often contains impurities including arsenic and phosphorous, which themselves can exert toxic effects potentially covering those of the test substance. The study conception is furthermore not compliant to the relevant OECD TG 407 guideline for a short-term repeated dose toxicity study. Several shortcomings include the use of only one sex (males), a lower number of total animals (6 instead of 10 animals per dose), and the use of two instead of three dose groups. This impairs a robust assessment of dose-dependency of effects. In addition, there was no justification for the selection of dose levels. Furthermore, a detailed list of findings for individual animals was not reported. Significant histopathological findings were only reported in the high dose group of calcium acetylide treatment and included desquamation of the lining epithelium of the stomach, necrosis of villi and different degrees of mucosal degeneration in the small intestine. These signs indicate that local effects could be involved in the observed signs of toxicity. Consequently, and especially in the light of the missing details on oral administration of calcium acetylide, the study design and reporting do not allow a thorough evaluation of the observed effects concerning the involvement of systemic or local non-specific mode of actions of the substance.
Based on the deficiencies described, evaluation of the inherent quality of the provided data with the ECVAM ToxRTool resulted in the assignment of Klimisch category 3 and thus the study was not regarded suitable for the assessment of repeated dose toxicity of the test substance calcium acetylide.
In addition, the long-term effects of calcium intake have been assessed in various in vivo and epidemiological studies (see IUCLID section 7.5.1, 7.7, and 7.10.3). Examples are the studies from Maekawa (1991) and Matsushima (1989). Here, the long-term toxicity/carcinogenicity of calcium (as calcium lactate, a food additive), was examined in rats in the drinking water at levels up to 5 % for 90 day and 2 years, respectively.
The low toxicity of acetylene is supported by several studies. Examples are Franken (1933, IUCLID section 7.5.2) and Reichert (1984, IUCLID section 7.7). Franken (1933) evaluated possible organ damage from the administration of acetylene at anaesthetic concentrations in rats, mice, guinea pigs, rabbits, and dogs. Animals were exposed to acetylene in oxygen for 0.5-2 h per day for up to 93 days. No effects on organs has been reported. Reichert (1984) assessed carcinogenicity of dichloroacetylene for up to 18 months, with acetylene as control.
Justification for selection of
repeated dose toxicity via oral route - systemic effects endpoint:
Repeated dose toxicity was assessed in a weight of evidence approach
taking into account hazard data on calcium and acetylene. The risk
assessment of calcium carbide is driven by local effects (respiratory
irritation).
Justification for selection of repeated dose toxicity inhalation -
systemic effects endpoint:
Repeated dose toxicity was assessed in a weight of evidence approach
taking into account hazard data on calcium and acetylene. The risk
assessment of calcium carbide is driven by local effects (respiratory
irritation).)
Justification for selection of repeated dose toxicity inhalation -
local effects endpoint:
See IUCLID section 7.10.3 and 7.9.3 for the assessment of
respiratory irritation.
Justification for selection of repeated dose toxicity dermal -
systemic effects endpoint:
Repeated dose toxicity was assessed in a weight of evidence approach
taking into account hazard data on calcium and acetylene. The risk
assessment of calcium carbide is driven by local effects (respiratory
irritation).
Justification for selection of repeated dose toxicity dermal - local
effects endpoint:
Repeated dose toxicity was assessed in a weight of evidence approach
taking into account hazard data on calcium and acetylene. The risk
assessment of calcium carbide is driven by local effects (respiratory
irritation).
Justification for classification or non-classification
The risk assessment of calcium carbide is driven by local effects to the lung (respiratory irritation) hence H335 is warranted. At concentration relevant for respiratory irritation (1-5 mg/m³), possible systemic toxicity of the decomposition products of calcium carbide, calcium hydroxide and acetylene, can be neglected.
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