Registration Dossier

Administrative data

Description of key information

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Diarsenic trioxide is not considered to be sensitising to skin, for several reasons (weight-of-evidence approach, expert judgement):

1) A literature search on potential sensitising effects of (inorganic) arsenic compounds yielded very few results. The available data has already been summarised in the ATSDR Toxicological Profile on Arsenic:

Examination of workers exposed to arsenic trioxide dusts in a copper smelter led Holmqvist (1951) to suspect that repeated dermal contact could lead to dermal sensitization. In support of this, Holmqvist (1951) found a positive patch test in 80% of the exposed workers compared to 30% in a control population. These data do suggest that workers may be sensitized to arsenic, but the high response rate in controls seems unusual. A much lower response rate (0.5%) was noted in another patch test study of dermal sensitization (Wahlberg and Boman 1986), and the few positive responses seemed to be due to a cross-reactivity with nickel. Mohamed (1998) evaluated 11 male workers at a tin smelting factory where arsenic trioxide levels ranged from 5.2 to 14.4 mg/m3. The workers experienced symptoms of generalized itch, dry and hyperpigmented skin, folliculitis, and superficial ulcerations. The authors concluded that arsenic-containing dust collected on the sweat on the workers’ skin, causing contact dermatitis. Studies in guinea pigs did not yield evidence of a sensitization reaction to inorganic arsenic (Wahlberg and Boman 1986)” [ATSDR].

The WHO Environmental Health Criteria Document (EHC 224, 2001) is somewhat more precise in stating that „sodium arsenite and sodium arsenate are not allergenic in the guinea-pig maximisation test (Wahlberg & Boman, 1986)“.

The few case report do not relate to a substantial number of people and are quite outdated. Further, at least partly, the reported observations appear to relate more to localised irritating/corrosive effects than to sensitisation (systemic allergic reaction).

2) Exposure considerations: Diarsenic trioxide is classified as a Category 1 Carcinogen and as Skin Corrosive Cat 1B (H314: Causes severe skin burns and eye damage). Thus is may be assumed that appropriate risk reduction measures are implemented and personal protective equipment is used when handling As2O3 to avoid/exclude any exposure (oral, dermal or inhalation) to this substance.

3) Animal welfare: Based on the overall toxicological profile of As2O3, most specifically because of its corrosive nature, it is not justifiable to conduct any new testing on sensitising properties in laboratory animals.

In conclusion, neither new experimental testing, nor the classification as a sensitiser is justified for diarsenic trioxide.

Migrated from Short description of key information:
Skin sensitisation: not sensitizing (according to GMPT test)

Justification for classification or non-classification

Diarsenic trioxide is not considered to be sensitising to skin, for several reasons (weight-of-evidence approach, expert judgement). Please see discussion section for details.