Carbon black

Endpoint summary

Description of key information

Oral exposure:

No acute toxicity via the oral route is not expected for untreated nanoforms of carbon black. The acute oral toxicity of untreated nanoforms of carbon black is very low; no clinical signs of toxicity were noted in rats treated by gavage with the maximum technically achievable dose (8,000 -10,000 mg/kg bw).

Inhalation exposure:

The weight-of-evidence does not indicate the potential of an acute inhalation hazard. A 5-day high-quality GLP repeated dose inhalation toxicity study by Ma-Hock et al. (2013) revealed no effects in rats at 10 mg/m3 (6h/d, 5d/wk). The MMAD in this study was in the submicron range (0.6 μm); the primary structure of the material was in the 50 - 100 nm range. There were no clinical effects, nor any changes found at necropsy, in haematology, acute phase proteins, histology (only the lung was investigated), or BAL fluid. Another well-reported and high-quality study by Vincent et al. (2001) showed no adverse effects in rats exposed for 4 hours to 4.6 mg/m3 of a non-nanoform of carbon black. In another study, Pauluhn et al 2009, exposed male rats to 229 mg/m3 Printex 90 carbon black (solid: nanoform, no surface treatment) for 6 hours (nose only) MMAD 2 µm; GSD 2.2. The animals tolerated the exposure well in this study.

Kang et al 2013 reported no mortality in male Sprague-Dawley rats which were exposed to Printex 90 carbon black aerosols for 6 hours/day for 3 days or for 2 weeks. The median mass aerodynamic diameter of carbon black aerosols averaged 2.08 µm (for aerosol prepared without sonication; group N) and 1.79 µm (for aerosol prepared without sonication; group S). The average concentration of carbon black during the exposure period for group N and group S was 13.08 ± 3.18 mg/m3 and 13.67 ± 3.54 mg/ m3, respectively, in the 3-day experiment. The average concentration during the 2-week experiment was 9.83 ± 3.42 mg/m3 and 9.08 ± 4.49 mg/m3 for group N and group S, respectively.

Further, it has been documented that at regulatory relevant concentrations as required in the conventional acute inhalation studies (up to 5 mg/L), dry powder aerosols of poorly soluble substances like carbon black tend to form conglomerates causing physical obstruction of the animals’ airways and impaired respiration and suffocation (Hoffman et al 2018). Death caused via this mode of action should not be misdiagnosed as toxic effect (see also OECD Guidance #39 on Inhalation Toxicity Studies 2018, section 69,).

Reference:

Thomas Hofmann, Lan Ma-Hock, Wera Teubner, Jasmin-Chasmina Athas, Nicole Neubauer, Wendel Wohlleben, Ulrich Veith, Nicole End, Sibylle Groeters, Bennard van Ravenzwaay and Robert Landsiedel. 2018. Reduction of Acute Inhalation Toxicity Testing in Rats: The Contact Angle of Organic Pigments Predicts Their Suffocation Potential APPLIED IN VITRO TOXICOLOGY Volume 4, Number 2, 2018

Dermal exposure:

An acute dermal toxicity study does not need to be performed because the substance does not meet the criteria for classification as acute toxicity or STOT SE by the oral route and no systemic effects have been observed in in vivo skin irritation and skin sensitisation studies.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from June 1978 to July 1978

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: S. Ivanovas GmbH & Co., Med. Versuchstierzuchten K.G., Kißlegg/Allgäu, Germany
- Age at study initiation: 38 days (male), 42 days (female)
- Weight at study initiation: 100 -105 g
- Fasting period before study: 15-16 hours
- Housing: single, in Makrolon cages
- Diet (e.g. ad libitum): ad lib
- Water (e.g. ad libitum): ad lib
- Acclimation period: not reported

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 0.5
- Humidity (%): 55 +/- 5
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): not reported

IN-LIFE DATES: From: June 1978 To: Jui 1978

Route of administration:

oral: gavage

Vehicle:

other: aqueous hydroxypropyl methyl cellulose (0.8%)

Details on oral exposure:

VEHICLE
- Concentration in vehicle: not reported (maximum technically achievable concentration)
- Amount of vehicle (if gavage): 50 mL/kg
- Justification for choice of vehicle:

MAXIMUM DOSE VOLUME APPLIED: not reported

Doses:

8000 mg/kg bw (maximum technically achievable concentration)

No. of animals per sex per dose:

20

Control animals:

no

Details on study design:

TEST ANIMALS: 10 male and 10 female Sprague-Dawley rats, from Ivanovas GmbH & Co., Kisslegg/Allgäu), weight between 100 and 105 g. Age at study begin: 38 days (male animals), 42 days (female animals). Animals were fed standard laboratory diet (Altromin), water was available ad libitum. Animals were held individually in macrolon cages in an air-conditioned room at 22 +/- 0.5 deg centigrade, and a relative humidity of 55% +/- 5%. EXPOSURE TO TEST SUBSTANCE: The test substance was applied via single gavage as suspension in 0.8% aqueous hydroxypropyl methyl cellulose E4M in a constant volumne of 50 mL/kg bw. Food was withdrawn 15-16 hours before administration of the test substance. POST EXPOSURE OBSERVATION PERIOD: 4 weeks. OBSERVATIONS/PARAMETERS: behaviour, food consumption, body weight gain. All animals were necropsied and macroscopically evaluated at the end of the post-observation period.

Statistics:

Not performed

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 8 000 mg/kg bw

Mortality:

There was no mortality.

Clinical signs:

other: There were no clinical signs of toxicity.

Gross pathology:

Findings at necropsy were unremarkable

Other findings:

Post-dose observation time was 4 weeks. There were no effects with regard to the behaviour of the animals.

Interpretation of results:

GHS criteria not met

Conclusions:

The acute oral LD50 value in rats is greater than 8000 mg/kg bw (maximum achievable concentration)

Executive summary:

No mortality and no signs of toxicity occured in a OECD 401 guideline study with rats at 8,000 mg/kg bw. Necropsy findings were unremarkable.

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 1977

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

no

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

other: aqueous hydroxypropyl methyl cellulose (0.8%)

Details on oral exposure:

TEST ANIMALS: 10 male and 10 female Sprague-Dawley rats per group, from Ivanovas GmbH & Co., Kisslegg/Allgäu), weight between 100 and 105 g. Age at study begin: 38 days (male animals), 42 days (female animals). Animals were fed standard laboratory diet (Altromin), water was available ad libitum. Animals were held individually in macrolon cages in an air-conditioned room at 22 +/- 0.5 deg centigrade, and a relative humidity of 55% +/- 5%. EXPOSURE TO TEST SUBSTANCE: The test substance was applied via single gavage as suspension in 0.8% aqueous hydroxypropyl methyl cellulose E4M in a constant volumne of 50 mL/kg bw. Food was withdrawn 15-16 hours before administration of the test substance. POST EXPOSURE OBSERVATION PERIOD: 4 weeks. OBSERVATIONS/PARAMETERS: behaviour, food consumption, body weight gain. All animals were necropsied and macroscopically evaluated at the end of the post-observation period.

Doses:

6350, 7900, 10000 mg/kg bw

No. of animals per sex per dose:

10 (in total 30 female and 30 male animals)

Control animals:

no

Details on study design:

The study was performed using the maximum technically feasible dose.

Key result

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 10 000 mg/kg bw

Mortality:

There was no mortality.

Clinical signs:

other: There were no clinical signs of toxicity

Gross pathology:

Findings at necropsy were unremarkable

Other findings:

None reported

Interpretation of results:

GHS criteria not met

Conclusions:

The acute oral LD50 value in rats is greater than 10,000 mg/kg bw (maximum technically feasible dose)

Executive summary:

No mortality and no signs of toxicity occured in a OECD 401 guideline study with rats at 10,000 mg/kg bw. Necropsy findings were unremarkable.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

not reported

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

other: Short-Term Inhalation Toxicity protocol (STIS)

Deviations:

no

Principles of method if other than guideline:

The study design covers three key elements of particle toxicity testing: 1) inflammation potency in the respiratory tract, 2) reversibility or progression of the effect and 3) deposition and bio-persistence of the particles in lung

GLP compliance:

yes

Test type:

other:

Limit test:

no

Species:

rat

Strain:

Wistar

Remarks:

strain Crl:WI (Han)

Sex:

male

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose/head only

Mass median aerodynamic diameter (MMAD):

>= 0.6 - <= 0.9 µm

Geometric standard deviation (GSD):

>= 0.6 - <= 0.8

Details on inhalation exposure:

Brush dust generators served for generation of test atmospheres. Generated dusts were mixed with compressed air in a glass tube, diluted with conditioned air (activated charcoal-filtered air, 22 ±2°C, 50 ± 20% relative humidity, flow rate 4.5 ± 0.3 m3/h) and passed via a cyclone into the inhalation system. The desired inhalation chamber concentrations were achieved by withdrawing/exhausting and replacing a portion of the dust aerosol air with conditioned supply air immediately before entering the chamber (6 m3/h). Mean flow rate through the inhalation chamber, measured at exhaust air, was 5.4 ± 0.3 m3/h for all concentrations (corresponding to an air change in the inhalation chambers of about 67 times per hour). Compressed and conditioned supply air and exhaust air flow rates, chamber temperature and humidity were measured automatically with appropriate sensors/orifice plates; data were saved every 10 s and retained for analysis. To ensure the stability of the dust aerosols, the inhalation chambers were monitored continuously during exposure using scattered light photometers. To quantify the atmospheric dust concentration, gravimetric measurements of air samples taken adjacent to the animals’ breathing zone were performed.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

30 h

Remarks on duration:

6h/day for 5 days

Concentrations:

0.5, 2.5, or 10 mg/m3

No. of animals per sex per dose:

11 male rats per dose

Control animals:

yes

Details on study design:

Groups of 11 male Wistar rats were head-nose exposed to respirable dusts on 6 hours per day, on 5 consecutive days (days 0 to 4). The target concentrations were 0.5, 2.5, or 10 mg/m3. A concurrent control group was exposed to conditioned air. On study day 4 (after the last exposure) and 25 (21 days after the last exposure), 6 animals per group were sacrificed and designated for histopathological examinations. On study day 7 (3 days after last exposure) and 28 (24 days after last exposure), the remaining 5 animals per group were sacrificed. The lungs of these animals were lavaged, and BALF was analyzed for markers indicative for injury of the bronchoalveolar region.

Statistics:

Dunnett’s test was used for simultaneous comparison of all concentration groups with the control group for body weights and body weight changes. Clinical pathologyparameters were analyzed by non-parametric one-way analysis using the Kruskal-Wallis test (two-sided). If the resulting p-value was equal or less than 0.05, a pair-wise comparison of each dose group with the control group was performed using Wilcoxon-test or Mann–Whitney-U-test (two-sided) for the equal medians. Statistical significance was defined as p ≤ 0.05 compared with the control group. Organ weights were compared among groups by nonparametric one-way analysis using the two-sided Kruskal–Wallis test, followed by a two-sided Wilcoxon test for the hypothesis of equal medians in case of p ≤ 0.05.

Key result

Sex:

male

Dose descriptor:

other: NOAEC

Effect level:

10 mg/m³ air (analytical)

Based on:

test mat.

Exp. duration:

30 h

Remarks on result:

other: There were no clinical effects, nor any changes found at necropsy, in haematology, acute phase proteins, histology (only the lung was investigated), or BAL fluid. No mortality was observed

Mortality:

No mortality was observed

Body weight:

No effects on body weights

Gross pathology:

No effects on organ weights; no pathological changes were noted at necropsy.

Other findings:

No compound-related adverse effects were found in hematology and histology. On study day 4, black particles (considered to be Carbon Black) were observed within´ alveolar macrophages in animals exposed to 10 mg/m3. In three of the six treated animals there was a minimal increase in numbers of alveolar macrophages.

Conclusions:

No compound-related effects were observed in rats exposed to Carbon Black

Executive summary:

Low surface area carbon black (32 -37m2/g) was tested in a 5 -day nose-only inhalation study in rats (6h/day, 5days/week). The MMAD was in the submicron range (0.6 μm). There were no clinical effects, nor any changes found at necropsy, in hematology, acute phase proteins, histology (only the lung was investigated), or BAL fluid.

Reference 2

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

GLP compliance:

no

Remarks:

data published

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

Carbon black dose was a single 6-h nose-only inhalation exposure at a concentration of 229 mg/m3, MMAD of 2.0 µm and GSD of 2.2. Rats of the control were nose-only exposed to air only. Pulmonary responses were examined by bronchoalveolar lavage (BAL) on postexposure days 7, 28, and 90.

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Mass median aerodynamic diameter (MMAD):

2 µm

Geometric standard deviation (GSD):

2.2

Duration of exposure:

6 h

Concentrations:

229 mg/m3

No. of animals per sex per dose:

details not provided

Details on study design:

BAL fluid was evaluated for inflammatory endpoints (lactate dehydrogenase, total protein, phospholipids, and neutrophils) and pro-inflammatory endpoints (interleukin [IL]-4, tumor necrosis factor [TNF]-alpha, granulocyte–macrophage colony-stimulating factor, and the chemokine monocyte chemotactic protein-1).

Sex:

male

Dose descriptor:

LC0

Effect level:

> 229 mg/m³ air (analytical)

Based on:

test mat.

Exp. duration:

6 h

Mortality:

Mortality in inffered from the results presented in the publication. The minimal effects noted in BAL fluid indicates that mortality in carbon black-exposured rats was unlikely at the exposure concentration of 229 mg/m3.

Other findings:

Findings were limited to an evaluation of inflammatory endpoints in BAL fluid.

Conclusions:

In this study evaluating multiwalled carbon nanotubes, carbon black was used as a reference material and quartz was used as a positive control. Compared to multiwalled carbon nanotubes and quartz, carbon black showed no increase in BAL protein even at day 90 of exposure. Carbon black showed a slight increase in BAL neutrophils compared to control, but the increase was much less than that seen for multiwalled carbon nanotubes and quartz. There was also no increase in total cell count. Overall, these results show that the rats tolerated well the concentration of carbon black Printex 90 adminstered for 6 hour.

Executive summary:

In this study evaluating multiwalled carbon nanotubes, carbon black was used as a reference material and quartz was used as a positive control.  Compared to multiwalled carbon nanotubes and quartz, carbon black showed no increase in BAL protein even at day 90 of exposure.  Carbon black showed a slight increase in BAL neutrophils compared to control, but the increase was much less than that seen for multiwalled carbon nanotubes and quartz.  There was also no increase in total cell count.  Overall, these results show that the rats tolerated well the concentration of carbon black Printex 90 adminstered for 6 hour.

Reference 3

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

Aerosols were prepared either with or without sonication to verify the effects of agglomeration on the toxicity and lung deposition of Printex 90. Male Sprague-Dawley rats were exposed to carbon black aerosols 6 hr a day for 3 days or for 2 weeks. The median mass aerodynamic diameter of carbon black aerosols averaged 2.08 µm (for aerosol prepared without sonication; group N) and 1.79 µm (for aerosol prepared with sonication; group S). The average concentration of carbon black during the exposure period for group N and group S was 13.08 ± 3.18 mg/m3 and 13.67 ± 3.54 mg/m3 respectively, in the 3-day experiment. The average concentration during the 2-week experiment was 9.83 ± 3.42 mg/m3 and 9.08 ± 4.49 mg/m3 for group N and group S, respectively.

GLP compliance:

not specified

Remarks:

The study is published in open literature

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

Five week-old male Specific pathogen-free (SPF) Sprague-Dawley (SD) rats were obtained from Central Lab Animal Inc. (Seoul, Korea) and were acclimatized at least 1 week prior to carbon black exposure. During the acclimation and experimental period, rats were housed at polycarbonate cages in a room with controlled temperature (23 ± 2°C), humidity (55 ± 7%), and a 12-hr light/dark cycle. Rats were fed filtered water and a rodent diet (LabDiet 5053, PMI Nutrition, USA) ad libitum. The study was approved by an animal ethics committee to ensure appropriate animal care for research

Route of administration:

inhalation: aerosol

Vehicle:

water

Remark on MMAD/GSD:

The mass median aerodynamic diameter (MMAD) of carbon black aerosols generated with sonication was not much different from that of aerosols generated without sonication (MMAD for group N and group S were 2.08 µm and 1.79 µm, respectively,

Details on study design:

Carbon black dispersions for both group S (aerosols generated with sonication) and group N (aerosols generated without sonication) were prepared by adding 1.5 g of carbon black in 300 ml of distilled water then were stirred vigorously for one minute, and additional sonication was applied to dispersion for group S in a probe type ultrasonicator.

Key result

Sex:

male

Dose descriptor:

LC0

Effect level:

13 mg/m³ air

Based on:

test mat.

Exp. duration:

18 h

Remarks on result:

not determinable due to absence of adverse toxic effects

Mortality:

no mortality

Interpretation of results:

GHS criteria not met

Conclusions:

Carbon black aerosol generated by sonication possesses smaller particles that are deposited to a greater extent in the lungs than is aerosol formulated without sonication.

Executive summary:

Male Sprague-Dawley rats were exposed to carbon black aerosols 6 hours/day for 3 days or for 2 weeks. The median mass aerodynamic diameter of carbon black aerosols averaged 2.08 µm (for aerosol prepared without sonication; group N) and 1.79 µm (for aerosol prepared without sonication; group S). The average concentration of carbon black during the exposure period for group N and group S was 13.08 ± 3.18 mg/m3 and 13.67 ± 3.54 mg/ m3, respectively, in the 3-day experiment. The average concentration during the 2-week experiment was 9.83 ± 3.42 mg/m3 and 9.08 ± 4.49 mg/m3 for group N and group S, respectively. The amount of carbon black deposition in the lungs was significantly higher in group S than in group N in both 3-day and 2-week experiments. The number of total cells, macrophages and polymorphonuclear leukocytes in the bronchoalveolar lavage (BAL) fluid, and the number of total white blood cells and neutrophils in the blood in the 2- week experiment were significantly higher in group S than in normal control. However, differences were not found in the inflammatory cytokine levels (IL-1β, TNF-α, IL-6, etc.) and protein indicators of cell damage (albumin and lactate dehydrogenase) in the BAL fluid of both group N and group S as compared to the normal control.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Data waiving:

other justification

Justification for data waiving:

the study does not need to be conducted because the physicochemical and toxicological properties suggest no potential for a significant rate of absorption through the skin

the study does not need to be conducted because the substance does not meet the criteria for classification as acute toxicity or STOT SE by the oral route and no systemic effects have been observed in in vivo studies with dermal exposure (e.g. skin irritation, skin sensitisation)

Justification for type of information:

Dermal Absorption studies by Hallegot et al 2011 and Johnson et al 2013, performed with not treated nanoforms of carbon black indicate lack of potential of these nanoforms to penetrate the skin. Transmission electron microscopy (TEM) analysis of the skin samples treated with eyeliner containing carbon black showed that particulate material (identified as carbon black) was only observed in the outer layers of the Stratum Corneum. There was no evidence of deeper penetration of carbon black material into the Stratum Corneum or into living epidermis Hallegot et al 2011. Johnson et al 2013 applying a test formulation containing not a not treated carbon black (with particle sizes between 20-30 nm) to full-thickness human skin samples in accordance with OECD 428 protocol could demonstrate no permeation of carbon black particles from a cosmetic eyeliner formulation into or beyond the outer layer of the stratum corneum was found.
This data waiving argument is valid for all forms of carbon black (non-nano, not treated and surface treated). Solubility studies in water and dissolution testing in biological fluids indicate a similar lack of insolubility for members of the sets of (nano)forms which also are not prone to release toxic moieties. Given the lack of solubility and particle sizes, treated forms (with particle sizes comparable to that of the not treated forms) and non-nanoforms (with particle sizes greater than that of the treated forms), are not expected to possess a higher skin higher penetration potential than what has been demonstrated for the not-treated forms by Hallegot et al 2011 and Johnson et al 2013.

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Endpoint conclusion

Endpoint conclusion:

no study available