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Sediment toxicity

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Description of key information

No data are available on the toxicity to sediment organisms of charcoal produced by wood.  
However, there are more data available related to sediments toxicity on activated carbon.
In conclusion, considering the relevant studies (for activated carbon), no adverse effects are expected to occur on sediments following exposure to charcoal.

Key value for chemical safety assessment

Additional information

No data are available on the toxicity to sediment organisms of charcoal produced by wood. 

However, there are more data available related to the effects on sediment organisms of the exposure to activated carbon. Activated carbon (AC) addition to sediments is a recently developed technique for the remediation of sediments contaminated with hydrophobic organic chemicals. Sediment amendment with this strong sorbent material is one alternativein situapproach for remediation to reduce exposure by reducing the (bio)availability of pollutants. Many laboratory studies and field experiments have been conducted during the last decade to investigate the possible adverse effects of AC sediment amendment on sediment organisms.

As revealed by the studies, the observed adverse effects on sediment organisms are inversely proportionate to the particle size of activated carbon, while smaller particle sized AC exhibits more severe adverse effects on sediment organisms. Taking into account the fact that the charcoal particle size is much higher than the activated carbon (> 90% of the charcoal particles have >10mm diameter) we consider that the read across procedure from activated carbon is a more conservative approach to evaluate the possible adverse effects on sediment organisms from their exposure to charcoal.

In (Cho, Ghosh et al. 2009)study the effects of field-scale application of activated carbon (AC) amendment to contaminated sediment in marine environment for in-situ stabilization of polychlorinated biphenyls (PCBs) was assessed. Among other the study investigated the possible adverse effects of this field application of AC to sediment organisms. The particle size of AC used in this study was 50 – 200μm and the measured AC doses were 2.0 – 3.2% (w/w dry sediment). As revealed by this study, the taxa richness and diversity were related to previously reported marine taxa in San Francisco. Therefore, no adversity impact was observed in the existing macro benthic community composition, richness or diversity.

In (Cornelissen, Elmquist Kruså et al. 2011) study, the effects on the benthic community were assessed following field application of powered activated carbon (AC) alone or in combination with sand or clay as a thin-layer capping material in marine environment. The dose of AC that have been used was not specified, however the amount of measured AC, 12 months after amendment ranged from 19 – 32% (w/w dry sediment). The particle size of AC used in this study was < 45μm. The results of this study indicated that the species abundance was reduced in all capping treatments compared to the reference. Species richness was also reduced in most of the treatments. In some cases the Shannon – Wiener index (H) and the benthic quality index (BQI) were reduced. However, high variation was observed between replicates due to low number of replicates from each site (n=1, 2 or 3).

In(Kupryianchyk, Peeters et al. 2012)study an application of powerded activated carbon (AC)(D50 =15 μm) was performed in different concentration in sediment. The effects on the recovery of benthic communities were assessed after short - (3 months) and long- term (15 months) of recolonization. The AC sediment amendment did not have any adverse effect on biodiversity and abundance of the benthic taxa, after 3 and 15 months of recolonization. The only negative effect was observed in Lumbriculidae and Pisidiidae families after 15 months. The study concludes that at the level of entire community the effects of AC addition to unpolluted sediment up to the concentration of ~4% w/w dry sediement were mild.

The first study (Cho, Ghosh et al 2009) seems to be more appropriate to estimate the effects of charcoal in sediment organisms considering the charcoal uses for two main reasons. Firstly, taking into account that the particle size of charcoal is > 1mm) we consider that the AC of 50 – 200μm used in Cho, Ghosh et al 2009 is more relevant to evaluate the effects of charcoal in sediment organisms than the AC of < 45μm used in Cornelissen, Elmquist Kruså et al. 2011study or the AC of 15μm used in (Kupryianchyk, Peeters et al. 2012)study. Secondly, the amount of AC that have been added to the sediment in Cornelissen, Elmquist Kruså et al. 2011study was extremely high (19 – 32% w/w dry sediment). We assume that these high concentrations are unlealistic to occur in real life considering the charcoal uses.

In conclusion, considering the above mentioned results no adverse effects are expected to occur on sediments following exposure to charcoal.