Charcoal

Genetic toxicity: in vitro

Administrative data

Endpoint:

genetic toxicity in vitro

Remarks:

Type of genotoxicity: gene mutation

Type of information:

other: Assessment

Adequacy of study:

key study

Study period:

May 2013

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Reliability score 2 on the basis of the weight of evidence found during review of public documents relating to mutagenicity of charcoal and similar carbon materials.

Data source

Reference

Reference Type:

other company data

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Qualifier:

no guideline followed

Guideline:

other: literature assessment

GLP compliance:

not specified

Type of assay:

other: literature assessment

Test material

Test material information

Constituent 1

Reference substance name:

Charcoal

EC Number:

240-383-3

EC Name:

Charcoal

Cas Number:

16291-96-6

IUPAC Name:

Charcoal

Results and discussion

Test results

Species / strain:

not specified

Metabolic activation:

not specified

Genotoxicity:

other: literature assessment

Cytotoxicity / choice of top concentrations:

other: literature assessment

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

The test material is considered to be non-mutagenic following assessment of available published data

Executive summary:

General

The test material charcoal (EC no 240-383-3) is a UVCB substance which consists of the following main constituents: carbon (amorphous), ash, volatile organic material of undetermined composition and moisture. There may be some trace elemental impurities dependent on the origin / source of the wood from which it is made.

The substance is typically of low purity with impurities including organic compounds derived from wood. None of the impurities are considered to impact on classification. The substance is not classified as dangerous for the environment or to health.

 

Indirect data

A search of available literature for direct mutagenicity tests on charcoal itself revealed very little. Where charcoal was cited it was usually because it had been used (as activated charcoal) for removal of toxins from raw waters⁽¹⁾or from cigarette smoke⁽²⁾or as an active carrier⁽³⁾prior to further testing for mutagenicity on other species. This in itself suggests that charcoal is not considered to be mutagenic in its own right since scientific studies would not be valid if the charcoal had contributed to the effect.

 

There is data or expert opinion available for other carbon materials that could be considered for ‘read-across’. In particular carbon black and carbon nanotubes have published data for mutagenicity testing.

 

Carbon Black data

Carbon black can be used as a ‘read-across’ substance for charcoal based on the following logic;

Charcoal is produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen. Activated charcoal is produced by exposure of charcoal to oxidizing atmospheres (carbon dioxide, oxygen, or steam) at temperatures usually in the range of 600–1200 °C. Charcoal is an impure form of amorphous carbon as it contains ash and other impurities but contains between 60 - 85% as fixed carbon.

Carbon black is a material produced by the incomplete combustion of heavy petroleum products as opposed to wood. Carbon black is a pure form of amorphous carbon that has a high surface-area-to-volume ratio in a similar way to activated charcoal.

Carbon black is a very pure form of amorphous carbon unlike charcoal but the vast majority of charcoal is amorphous carbon and therefore it is reasonable to assume that carbon black (CAS1333-86-4) can be used as a ‘read-across’ substance for the purpose of end point data.

 

The OECD SIDS Report for Carbon Black⁽⁴⁾gives the following assessment for mutagenicity;

In vitro, carbon blacks were non-mutagenic in various Ames tests, whilst organic extracts can exhibit a wide variety of activity, depending on the conditions of extraction. This activity is ascribed to mutagenic organic impurities (mainly polycyclic aromatic hydrocarbons) in the extract. Carbon black was tested negative in a mouse lymphoma assay, and did not induce sister chromatid exchanges in Chinese Hamster Ovary cells. 

The mutagenic activities of carbon black extracts varied widely, and both negative and positive Ames test results are reported in the literature. A mutagenic activity was generally ascribed to mutagenic PAH materials that were present as impurities in the carbon black. (There are no such PAH substances in charcoal).

In summary the OECD report concluded that the available evidence strongly suggests that Carbon Black is not directly mutagenic and that mutations are caused by secondary mechanisms.

 

Carbon nano form data

The main constituent of charcoal is elemental carbon, therefore it is reasonable to read-across to data that has been obtained by using pure elemental carbon sources such as activated carbon and nano carbon forms.

 

A study using activated carbon nanoparticles (ACNP) has shown that it can decrease the genotoxicity and teratogenicity of mitomycin C (MMC) used in cancer treatment in humans⁽⁵⁾.

This study appears to use a test method similar to a regulatory method (lung fibroblasts) and shows that adding activated carbon reduces mutagenicity of a known toxin.  This clearly shows that the carbon itself is non-mutagenic.

Another study on single walled carbon nanotubes⁽⁶⁾concluded that there was no mutagenic effect by this material

Human observation

Only one study was found which related to this end point which was done on the urine of charcoal workers in Brazil⁽⁷⁾. This study reported measurement of internal exposure to wood smokeamong charcoal workers, and the results showed that these workers receive a systemic exposure to genotoxic compounds. But this was attributed to the volatile organic compounds that are produced during the ‘charring’ process and not to the actual charcoal itself.

Conclusion

In the absence of direct data relating to the mutagenicity effect of charcoal, evidence gathered from published scientific reports and from read-across to other elemental carbon substances strongly suggests that charcoal is not mutagenic