Aluminum, dross

Endpoint summary

Description of key information

From the acute inhalation toxicity test (endpoint 7.2.2), it was not possible to grind the test substance to a fine powder able to generate an appropriate inhalation atmosphere for testing as shown in the feasibility report. According to REACH Regulation, Annex XI, a study needs not be performed if there are technical obstacles. According to ECHA guidance document R7.A for inhalation route, no testing is required if it is not technically possible to generate a testing atmosphere. Read-across to individual constituents and degradation products is ventured for C&L purposes.
Regarding studies on the individual constituents of aluminium dross i) the read-across study on aluminium metal (endpoint Aluminium_metal_Gross_et_al_1973) was actually a subchronic toxicity study (180 days) ii) the read-across study on aluminium oxide used (endpoint Aluminium_Oxide_Gross_et_al_1973)  was actually a subchronic toxicity study (180 days) iii) the read-across study on ammonia (endpoint Ammonia_Coon_et_al_1970) was actually a subchronic toxicity study (90 days). Both of the studies i) and ii) revealed a NOAEL resulting in a DNEL comparable to occupational limits for total dusts (TWA 10 mg/m3). Exposure of general population to respirable/inhalable fractions of Aluminium dross is not expected. Therefore, safe use of Aluminium dross is ensured based on the results of the subchronic studies of Aluminium dross constituents, hence no longer term studies are proposed.
A LOAEC of 50mg Aluminium metal dust/m3 was selected for the derivation of DNEL.

Key value for chemical safety assessment

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEC

187.5 mg/m³

Study duration:

subchronic

Species:

rat

Additional information

Repeated oral exposure is not relevant under the given industrial settings of production of Aluminium dross and the Risk Management Measures that are applied. The workers dine away from the areas where aluminium dross is being processed and work with personal protective equipment. Escape to the environment is considered unlikely due to the processing taking place in a contained area.

Repeated dermal exposure is not relevant under the given industrial settings of production of Aluminium dross and the Risk Management Measures that are applied. 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 this test.

From the acute inhalation toxicity test (endpoint 7.2.2), it was not possible to grind the test substance to a fine powder able to generate an appropriate inhalation atmosphere for testing as shown in the feasibility report. According to REACH Regulation, Annex XI, a study needs not be performed if there are technical obstacles. According to ECHA guidance document R7.A for inhalation route, no testing is required if it is not technically possible to generate a testing atmosphere. Read-across to individual constituents and degradation products is ventured for C&L purposes.

Repeated exposure of workers to Aluminium dross is relevant under industrial settings. It is not technically feasible to perform a subchronic or subacute inhalation study with Aluminium dross. Read across to its individual substances revealed that

1)     Subchronic inhalation of aluminium metal was characterised by dust accumulation in lung parenchyma but and alveolar proteinosis which was later diminished. A LOAEC of50mg Al2O3/m3 was established which would correspond to 187.5 mg Aluminium dross/m3. This is an underestimation of a 90-day LOAEC since the animals were exposed for a total of 180 days.

2)     Subchronic inhalation of aluminium oxide was characterised by dust accumulation in lung parenchyma but no histopathological lesions. A NOAEC of75mg Al2O3/m3 was established which would correspond to 125 mg Aluminium dross/m3. This is an underestimation of a 90-day NOAEC since the animals were exposed for a total of 180 days.

3)     Subchronic inhalation of ammonia, like this which will be produced upon inhalation of Aluminium nitride of Aluminium dross is characterised by a NOAEC of 300.3 mg ammonia which would correspond to 2001.8 mg Al dross/m3 in case the whole quantity of AlN reacted with water to produce Aluminum Hydroxide and Ammonia. Aluminum Hydroxide is known to have no toxicological activity, in fact it is used for medicinal purposes. A DNEL for long term-local effects/inhalation can be derived from the above mentioned values.

4)     Chronic epidemiological studies on inorganic aluminium substances (metallic aluminium and aluminium oxide dust and fumes) may give added information on effects after inhalation of the substance. From these data it was shown that compromised respiratory function and/or asthmatic reactions may be observed in industrial environments characterised by aluminium species presence. It is unclear however if other irritating constituents (e.g. fluorides) are more or exclusively responsible for these symptoms. Serious nosological entities are due to a type of pneumonoconiosis (aluminosis) and they were observed very high ambient particulate concentrations which should not be encountered anymore in legitimate industrial settings. Neurological symptoms have not been encountered in industrial exposure to inorganic aluminium substances. Subclinical neurological and psychomotor symptoms have been found in some studies but there are no robust data on concentrations and types of aluminium substances that have caused them.

 

The information on the repeated dose toxicity is adequate for a robust characterization of the toxicological hazards including an estimate of a dose descriptor (NOAEL/LOAEL) and the data are adequate for risk assessment and classification.

The following information is taken into account for hazard/risk assessment

Subacute toxicity: oral

-not probable route of exposure

Subcute toxicity: inhalation

- study technically not feasible

-LOAEC (aluminium metal)=50 mg/m3 (subchronic), which translates to about 200mg (Al dross)/m3

-NOAEC (aluminium oxide)=75 mg/m3 (subchronic), which translates to about 187,5 mg (Al dross)/m3

Subacute toxicity: dermal

-not probable route of exposure

Justification for classification or non-classification

No studies on repeated dose toxicity via dermal or oral route of exposure have been performed since this route of exposure is not relevant for industrial setting provided that standard risk management measures and hygienic procedures are applied. Repeated dose toxicity via inhalation was not technically feasible, so read-across to individual substances was ventured. Two subchronic studies revealed no mortalities, hence no LC50 could be established for the substance at those concentrations. A LOAEC and a NOAEC were respectively derived, which provide a DNEL comparable to current OELs for aluminium. Furthermore both aluminium metal and aluminium oxide (as well as aluminium hydroxide) have been characterized as a non-hazardous nuisance dust (the higher the concentration of dust the greater the risk of irritation to the respiratory system and mechanical irritation to the eyes). Finally, serious nosological entities are due to a type of pneumonoconiosis (aluminosis) and they were observed very high ambient particulate concentrations which should not be encountered anymore in legitimate industrial settings. Neurological symptoms have not been encountered in industrial exposure to inorganic aluminium substances. Subclinical neurological and psychomotor symptoms have been found in some studies but there are no robust data on concentrations and types of aluminium substances that have caused them.As a result no classification for acute toxicity is proposed