Charcoal

Endpoint summary

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Limited data are available in the scientific literature with regard to the toxicity of the examined charcoal in mammals. All these data involve mainly the study of beneficial effects of charcoal consumption by animals and not the identification of any hazardous properties of charcoal.

Although actual toxicity data on charcoal were not found,the toxicity of carbon black of hydrocarbon origin has been examined in a series of studies and has been reviewed extensively worldwide [IARC (1996), US EPA (2005), OECD (2006)etc.].

Carbon black is a powdered form of elemental carbon composed of particles and fused particle aggregates (McCunney 2001). It is manufactured by the controlled vapour-phase pyrolysis and partial combustion of gaseous or liquid hydrocarbons (IARC 1996; US EPA 2005). Depending on the specific process by which it is manufactured, carbon black can be further classified as acetylene black, gas black, channel black, furnace black, lampblack, or thermal black (IARC 1996; OECD 2006). The most critical constituent of carbon black from a toxicological point of view are the Polycyclic Aromatic Hydrocarbons (PAHs) derived from the source material used to produce carbon black. Considering that charcoal is derived from vegetable material it is considered unlikely that higher levels of PAHs would be present in charcoal compared to carbon black. This hypothesis has been confirmed by the chemical analysis of charcoal, where PAHs have not been detected (<0.1 ppm). In addition, the available toxicokinetic data on carbon black concern nanoparticles of a 27 nm diameter, while in the charcoal sample, only 0.11-0.36% of the examined material was found to have a diameter below 100μm.

It is noted that in a recent evaluation by EFSA (Scientific Opinion on the re-evaluation of vegetable carbon, E 153, as a food additive1 EFSA Panel on Food Additives and Nutrient Sources added to Food, ANS2, 3 European Food Safety Authority (EFSA), Parma, Italy, EFSA Journal 2012;10(4):2592)

, for “vegetable carbon” (in form of activated carbon) as a food additive, data on carbon black have also been used. The fact that these data have been accepted as relevant for the evaluation of a food additive which will be consumed by the general public, reinforces the approach to use these data on the assessment of charcoal.

In addition to carbon black data, extensive literature can be found also on activated charcoal. The examined charcoal has a fix carbon content about 76.3% w/w (ranging from 75 to 88.05% w/w). With regard to the carbon content of charcoal it can be considered that this is characterized by similar hazardous properties as other carbon forms, i.e. vegetable carbon (E153, used as food additive) and activated carbon. In addition, the most significant difference between the examined charcoal and activated carbon/vegetable carbon (apart from the impurity content) is the particle size distribution. Charcoal contains practically no fine particles [only a fraction of0.11-0.36 %of the analysed sample has a diameter lower than 100μm] while the activation process of activated carbon/vegetable carbon produces 90% particles of a size of <55μm.

It is acknowledged that activated charcoal is of higher purity compared to charcoal sincecharcoal has not been processed in order to be activated, resulting in the existence of a high percentage of impurities (average percentages: 18.93% volatiles, 4.19% moisture, 3.21% Ash).However, taking into account that PAHs have not been detected in the charcoal samples and that the analysis for volatiles has showed that none of these compounds contribute to the toxicity of charcoal, it has been considered that the data on activated charcoal can also be used on the configuration/determination of the toxicological profile of charcoal.

Studies on goat and monkeys, showed that charcoal from vegetable origin exhibit similar absorptive properties as activated charcoal (Van et al., 2006 and Struhsakeret al., 1997).

As mentioned above, it has been concluded that toxicokinetics data on carbon black and activated charcoal/vegetable carbon can be used on a read-across basis for the toxicological assessment of charcoal (with regard to the carbon fix content).

Experiments on mice using radiolabelled carbon black of a 27 nm diameter, produced from the furnace process, showed that extremely low radioactivity was detected in extraintestinal viscera and blood and that practically all the label was excreted in the faeces.Considering that carbon black of a 27 nm diameter was not absorbed by the oral route it can be assumed that charcoal which has only a 0.11-0.36% fraction of a diameter below 100μm will also not be absorbed.

Activated charcoal is known to have the same behavior following ingestion.

Overall, based on read-across activated charcoal and carbon black data, and it can be concluded that charcoal is not absorbed following oral administration and that the main route of excretion is via feaces.