Watch your blind spot: how chemical regulations drive regrettable substitution

Chemical regulations seek to protect human health and the environment by controlling risks from hazardous chemicals and promoting their substitution with safe(r) alternatives. Regulatory frameworks such as the EU/UK REACH (the registration, evaluation, authorisation and restriction of chemicals) and the Stockholm Convention (SC) are widely regarded as key mechanisms for driving such substitution. However, instances of regrettable substitution (RS), that is the replacement of hazardous chemicals with another that is equally harmful or the shifting of impacts from one concern to another raise questions about how effective these regulatory goals are being achieved. This article explores whether and how REACH and the SC may unintentionally exacerbate RS. Drawing on empirical analysis of regulatory practice across three illustrative substance groups, per-and polyfluoroalkyl substances (PFAS), bisphenols and flame retardants, we use an explanatory sequential mixed methods approach which integrate online questionnaire with in-depth semi-structured interviews and document analysis. The study identifies nine interconnected sets of systemic and operational regulatory challenges that inadvertently exacerbate RS. The findings indicate that RS is exacerbated not by regulatory intent, but by features of regulatory design and implementation, including fragmented and uncertain regulatory landscapes, prioritisation of market access over substance-level evaluation, trade-offs between internal market functioning and risk management, persistent data availability and interpretation challenges, and limited regulatory capacity, enforcement, and information sharing. By clarifying how these challenges arise within REACH and the SC, this article contributes needed insights into why substitution outcomes may diverge from regulatory objectives and provide a basis for informed policy discussion aimed at strengthening chemical regulation to better prevent harmful substitution and support safe(r), more sustainable chemical production and use.