Slags, ferronickel-manufg.

Endpoint summary

Description of key information

Chronic dermal and chronic oral toxicity are not considered relevant in the case of ferronickel slags.Additionally, no toxicity effects were observed on an in vivo acute skin irritation test (see relevant endpoint), while the low solubility of the constituents and the absence of dermal toxicity effects for the degradation products show no need for the test.Repeated oral exposure is not relevant under the given industrial settings of production and uses of Ferronickel Slags and the RMM that are applied.The workers dine away from the areas where slag is being processed and work with personal protective equipment.No studies on adverse toxicological effects through chronic inhalation exposure to ferronickel slags are known to exist.In order to avoid testing on live animals it was decided to assess the chronic inhalation toxicity potential of the slags based on the toxicological profile of the individual constituents, supplemented by data collected from findings of toxicological tests performed on the substance.Overall the data on inhalation toxicity are sufficient and allow for robust risk characterization of ferronickel slags.The only considerable hazard is attributed to the contained Nickel metal, which was found to produce toxic effects on the lungs in the form of fine nickel dust. However, the low content of both slags in Nickel metal, the coarseness of the substance's granulometry, Nickel's non-existent solubility (endpoint 4.8) and it being chemically bound in the slag matrix can lead to the cocnlusion that no adverse effects are expected from the substance. The rest of the constituents do not present a chronic hazard.A NOAEC of 0.1mg/m3 was identified for Nickel metal which translates to at least 25mg/m3 for ferronickel slag (with the worst case scenario of 0.4% Ni content).This is a strict result, because ferronickel slags are much more coarse than the tested material (only 10% of the inhalable fraction, which itself is only 6% of total dust, are below 5μm)

Key value for chemical safety assessment

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Dose descriptor:

LOAEC

25 mg/m³

Study duration:

chronic

Species:

rat

Additional information

Chronic dermal and chronic oral toxicity are not considered relevant in the case of ferronickel slags. No absorption occurs through the skin and also exposure of skin to the substance is negligible. Repeated oral exposure is not relevant under the given industrial settings of production and uses of Ferronickel Slags and the Risk Management Measures that are applied. The workers dine away from the areas Ferronickel slag is being processed and work with personal protective equipment.

No studies on adverse toxicological effects through chronic inhalation exposure to ferronickel slags are known to exist. In order to avoid testing on live animals it was decided to assess the chronic inhalation toxicity potential of the slags based on the toxicological profile of the individual constituents, supplemented by data collected from findings of toxicological tests performed on the substance. The slag in question is the one that contains the highest quantities of Calcium Oxide and Nickel metal among the various qualities of ferronickel slags and it was chosen to be tested for this reason. Silicon Dioxide can be found in either amorphous or crystalline form.Of the two, amorphous silicon dioxide is known to be of very lower toxicological potential compared to the crystalline form. In general, the toxicity of SiO₂increases with smaller particle size. Slags, ferronickel-manufg is a coarse material, with only 6% of its weight passing through a sieve with a 75μm mesh size and only approximately 17% of this fraction being smaller than 10μm. So, only 1% (approximately) of the total substance can be considered respirable (since larger particles are considered to be filtered earlier in the respiratory system and cannot easily reach the lungs). Under these circumstances, it can be concluded that the presence of SiO₂in ferronickel slags cannot produce any adverse health effects and they Silicon Dioxide does not need to be taken into further consideration. The fine particle fraction of various grades of Ferronickel Slags was analysed with XRD using Rietveld quantitative phase analysis to determine the respirable crystalline silica (RCS) content. As a result no RCS was detected, so it is safely assumed that the SiO2 in the substance is amorphous.

The chromium species were determined via alkaline digestion and colorimetric analysis (EPA 3060A and EPA 7196A respectively). No hexavalent Chromium species were present up to the limit of detection of the analytical method (20mg/kg) so all Cr in the substance is considered to be in trivalent form.

It should be noted that the substance cannot be classified as a mixture, because its various known constituents are chemically bound in various phases and are not separated easily. This also means that any toxicity presented by these constituents is expected to be lower in the slag due to the constituents not being freely available. CaO is strongly irritating and corrosive for mucous membranes. A study on chronic exposure of workers to also verifies the irritating potential of this substance. However, CaO in the slags is chelated with the rest of the non-irritant constituents of the slag matrix which renders invalid its inherent irritation potential. This has been verified in the acute oral and inhalation toxicity experiments on ferronickel slags (see endpoints 7.2.1 and 7.2.2 respectively) as well as in the skin and eye irritation experiments and in the sensitization experiments (see endpoints 7.3 and 7.4). It is thus concluded that Calcium Oxide is of negligible toxicity in the ferronickel slags.

Additionally these magnesium and silicon oxide are of insignificant toxicological profile. The same is true for Cr(III) compounds which have been proven to be devoid of cytotoxic and genotoxic characteristics both in humans and experimental animals.

Regarding iron and iron oxides, results from intratracheal instillation of ferrous oxide are suggestive of biochemical alterations of the lung in occupational siderosis but not of overt toxicity. A number of case studies on occupational exposure to iron dust show that siderosis is a benign pneumonoconiosis and that fibrosis is not a requisite in siderosis.

Subchronic and chronic experiments of inhalation of aluminium oxide show that the substance was not toxic for the lung or other target organs and it did not produce systemic toxicity. Compromised respiratory function has been observed in industrial environments (human data) characterised by aluminium species' presence but a variety of contaminants besides aluminium dust coexisted, that could have caused those effects. Under today's working conditions lung fibrosis induced by aluminium dust is not expected to occur anymore, as long as relevant OELs are followed.

Nickel metal was toxic for the lung in a relevant in vivo experiment. The result should be extrapolated with caution to humans because of the highly respirable size of the test item. Lung toxicity of Ni compounds is higher for the most water soluble Ni substances. Non-lethal respiratory effects (besides cancer) have been observed in groups occupationally exposed to nickel compounds but no robust risk characterization can be achieved from these studies.

Overall the data on inhalation toxicity are sufficient and allow for robust risk characterization of ferronickel slags. The only considerable hazard is attributed to the contained Nickel metal, which was found to produce toxic effects on the lungs in the form of fine nickel dust. However, the low content of both slags in Nickel metal, the coarseness of the substance's granulometry, Nickel's practically non-existent solubility (as was shown in endpoint 4.8) and it being chemically bound in the slag matrix can lead safely to the cocnlusion that no adverse effects are expected from the substance. The rest of the constituents do not present a chronic hazard.

Repeated dose toxicity: inhalation - systemic effects (target organ) respiratory: lung

Justification for classification or non-classification

No studies on adverse toxicological effects through chronic inhalation exposure to ferronickel slags are known to exist. In order to avoid testing on live animals it was decided to assess the chronic inhalation toxicity potential of the slags based on the toxicological profile of theindividual constituents in a read-across approach, supplemented by data collected from findings of acute toxicological experiments performed on a slag from a ferronickel factory. The slag in question is the one that contains the highest quantities of Calcium Oxide and Nickel metal among the various qualities of ferronickel slags and it was chosen to be tested for this reason.

After analysing of the fine particle fraction of various grades of Ferronickel Slags with XRD using Rietveld quantitative phase analysis to determine the respirable crystalline silica (RCS) content, practically no RCS was detected, so it is safely assumed that the SiO2 in the substance is amorphous and, therefore, not liable for repeated dose toxicity.

The ferronickel slags has been concluded that are not expected to have toxic effects due to chronic exposure based on the chronic toxicity of the constituents. Of the constituents of the ferronickel slag, Nickel metal is the only one that has been classified in terms of repeated dose toxicity, as STOT-RE 1, respiratory tract only. If it is assumed that ferronickel slags are mixtures containing freely available nickel metal, a content of at least 1% Ni-metal would be required to characterise the mixture as STOT-RE Cat.2. The highest possible content is 0.4 -0.6% Nickel which is well below that threshold.

Furthermore, the rest of the constituents have not been characterised as chronic toxic substances.

It is thus concluded that no classification is necessary in regards of Repeated dose toxicity for all ferronickel slags.