Neurotoxic chemicals

As there is no specific hazard class for neurotoxicity under REACH Article 57, such substances may be considered under the category Equivalent Level of Concern (ELoC).

In 2025, two consecutive studies were conducted by ChemSec and expert consultants to assess the potential of neurotoxicants to be identified as SVHC via the ELoC route. The first focused on substances with harmonised classification under Classification, Labelling and Packaging (CLP) legislation (primarily STOT RE 1 with neurotoxic endpoints). This was followed by a project extending the scope to substances without relevant harmonised classification, using data sources beyond the Classification & Labelling inventory. For the SIN List update in 2025, only chemicals with STOT RE 1 harmonised classification under CLP were included.

Methodological approach

Toxicity data were evaluated for potency, severity, irreversibility, and delay of effects, consistent with ELoC criteria. Human data were prioritised, although for most shortlisted substances evidence consisted of case reports or occupational studies rather than large-scale epidemiology. Based on a detailed evaluation of the shortlisted substances and supporting data, we identified three priority candidates as particularly strong cases for ELoC. To strengthen the assessment, an independent expert review was carried out by Joëlle Rüegg, professor of environmental toxicology at Uppsala University. 

Our conclusion is that neurotoxic substances can be systematically identified for ELoC assessment using structured screening, weight-of-evidence evaluation, and expert review. While data gaps remain significant, especially regarding long-term epidemiology, the irreversible nature of many neurotoxic outcomes confirms their equivalence in concern to other SVHC categories. 

The three substances included on the SIN List due to their neurotoxicity are:

Dimethyltin dichloride (CAS 753-73-1)

Neuropathological lesions (including effects on the brain) at low doses showcase high potency. The persistent neurological effects shown in both human and animal data, together with the developmental neurotoxicity observed, support the assessment that effects are irreversible. 

Methyltin mercaptide (CAS 57583-35-4)

Neuropathological lesions (including effects on the brain) at low doses showcase high potency. These effects are unlikely to reverse, which together with the developmental neurotoxicity observed, support the assessment that the effects are irreversible.

Sodium pyrithione (CAS 3811-73-2)

Neuropathological lesions at low doses showcase high potency. Nerve and muscle degeneration was irreversible.