Ashes (residues), cenospheres

Endpoint summary

Description of key information

Based on read across following an analogue approach:
Oral: LD50 (rat) > 2000 mg/kg bw
Inhalation: LC50 (rat) > 1400 mg/m³ (respirable fraction), > 5000 mg/m³ (total ashes (residues), cenospheres)
Dermal: no studies available

Additional information

There are no substance specific data available on the acute toxicity of ashes (residues), cenospheres.

Ashes (residues), cenospheres and ashes (residues), coal share a common production process as substances derived from coal combustion. ashes (residues), cenospheres represent a fraction of ashes (residues), coal separated by physical means. Both substances exhibit similarities in physicochemical properties and chemical composition. The main differences consist in a much lower content of water soluble matter and the particle size distribution of ashes (residues), cenospheres.

In terms of hazard assessment, studies available for ashes (residues), coal are therefore taken into account by read-across following an analogue approach, the results of these studies being considered a worst case for ashes (residues), cenospheres.

Oral

The acute toxicity of ashes (residues) after oral administration to Wistar rats was investigated according to EU Method B.1 tris under GLP conditions. Two groups of 3 female rats each were given the test material by gavage at 2000 mg/kg bw as a suspension in 0.5% methyl cellulose in water. No mortalities occurred and no clinical or pathological signs of toxicity were noted during the observation period of 14 days. The oral LD50 value for female rats was therefore considered to be greater than 2000 mg/kg bw (Rösslerová, 2008).

 

Inhalation

Male Sprague-Dawley rats were exposed to 1400 mg/m³ coal fly ash derived from a 400- MW power plant burning bituminous coal from multiple mines in the Wasatch Plateau, UT, for 4 h on three consecutive days. The average concentration of coal fly ash particulate matter less than 2.5 µm was 1400 mg/m³, out of which 600 mg/m³ was less than 1 µm. The observation period was 18 and 36 hours after the last exposure. At this time points, groups of animals were sacrificed for further examinations. Bronchoalveolar lavage, lung tissue and blood samples were analysed. No mortalities occurred. Histopathologic changes in the lung (focal alveolar septal thickening, increased cellularity, elevation in the number of alveolar macrophages with iron-positive cytoplasmic inclusions) and significant increase in neutrophils, both in the lung BALF and in the blood were noted (Smith, 2006). Based on these results, the LC50 value for male rats was assumed to be greater than 1400 mg/m³ of respirable coal fly ash particles.

The respirable fraction of ashes (residues), cenospheres typically accounts for < 1.5% of the total mass (s. Particle size distribution). Accordingly, the LC50 of total ashes (residues), cenospheres is expected to exceed 5000 mg/m³ (5 mg/L).

 

Dermal

This information is not available.

According to Section 8.5.3, Column 2 of Annex VIII to Regulation (EC) No 1907/2006, testing for acute toxicity by the dermal route is appropriate if: (1) inhalation of the substance is unlikely; and (2) skin contact in production and/or use is likely; and (3) the physicochemical and toxicological properties suggest potential for a significant rate of absorption through the skin.

Inhalation is the most relevant route of exposure for ashes (residues), cenospheres. Skin contact in production and/or use cannot be ruled out. However, based on the following considerations on physicochemical and toxicological properties, ashes (residues), cenospheres are not expected to cause death or any other systemic or local toxic effect after acute dermal exposure:

Ashes (residues), cenospheres are solid inorganic particles mostly composed of water insoluble compounds. Thus, no significant rate of absorption through the skin is expected.

The results of studies on acute oral and inhalation toxicity as well as on skin/eye irritation and skin sensitisation conducted with the analogue substance ashes (residues), coal showed no acute systemic toxicity after oral and inhalation exposure and no skin/eye irritation or skin sensitisation potential.

Therefore, based on the available data on the physicochemical properties of the ashes (residues), cenospheres as well as on toxicological data from the analogue substance ashes (residues), coal, systemic and/or local toxic effects after acute dermal exposure are unlikely to occur. Hence, testing on the acute dermal toxicity of the substance is not considered necessary and should be avoided for the sake of animal welfare.

Justification for classification or non-classification

Based on read-across following an analogue approach, the available data on the acute toxicity of ashes (residues), cenospheres is conclusive but not sufficient for classification according to the DSD (67/548/EEC) and GHS (CLP, 1272/2008/EC) criteria for classification and labelling.