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Administrative data

Description of key information

No studies of skin or eye irritation are available with sulphur trioxide.  Studies have been performed with diluted sulphuric acid (5% and 10% provide conflicting results depending on the volume, species, protocol and evaluation criteria and have not been evaluated.

Key value for chemical safety assessment

Eye irritation

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Additional information

Skin irritation

No studies of skin irritation have been performed and none are proposed. Sulphur trioxide will rapidly react with moisture present in the skin to produce sulphuric acid. Sulphuric acid is listed on Annex I of Directive 67/548/EEC with classification as 'CORROSIVE' (R35) 'Causes severe burns'. Specific concentration limits are R35 for concentrations of >=15%; 'IRRITANT' (R36/38) 'Irritating to eyes and skin for concentrations of >=5% to <15%.

No studies of dermal irritation / corrosion have been performed with concentrated sulphuric acid and none are proposed, based on scientific considerations and for reasons of animal welfare. Regulatory studies performed with 0.5 ml of 10% sulphuric acid indicate that this material is not classified as a skin irritant according to US criteria (summarised in OECD SIDS).

Based on the classification and labelling of sulphuric acid under Directive 67/548/EEC, it is considered that the hazard has been adequately characterised.

Eye irritation

No studies of eye irritation have been performed and none are proposed. Sulphur trioxide will rapidly react with moisture present in the skin to produce sulphuric acid. S

u lphuric acid is listed on Annex I of Directive 67/548/EEC with classification as 'CORROSIVE' (R35) 'Causes severe burns'. Specific concentration limits are R35 for concentrations of >=15%; 'IRRITANT' (R36/38) 'Irritating to eyes and skin for concentrations of >=5% to 15%.

No studies of eye irritation have been performed with the substance and none are proposed, based on scientific considerations and for reasons of animal welfare. Regulatory studies performed with 5% or 10% sulphuric acid are conflicting, depending on the species tested, volume, concentration and evaluation criteria.

Based on the classification and labelling of sulphuric acid under Directive 67/548/EEC, it is considered that the hazard has been adequately characterised.

Respiratory irritation

Sulphur trioxide reacts rapidly with atmospheric moisture and moisture in the respiratory tract to form sulphuric acid. The corrosive nature of the substance, the findings in inhalation studies performed with sulphuric acid and findings following occupational exposure to sulphuric acid aerosols and mists indicate that sulphur trioxide is a respiratory irritant.

Effects on eye irritation: irritating

Effects on respiratory irritation: irritating

Effect level: empty Endpoint conclusion: Adverse effect observed

Justification for classification or non-classification

Sulphur trioxide is not listed on Annex I of Directive 67/548/EEC.

Based on read-across from sulphuric acid, classification of sulphur trioxide as 'CORROSIVE' (R35) 'Causes severe burns' is proposed.