Background:

The e-cigarette market is rapidly growing, with over 1,800 substances potentially present in e-liquids—many lacking inhalation-specific toxicological data. Although Belgian and EU legislation permits only safe ingredients, there is no structured framework for systematic assessment or approval. Regulatory strategies can target addictiveness, attractiveness, and toxicity. In its focus on toxicity, Belgium wants to emphasize the risks associated with inhalation exposure. A new framework is being developed to create a whitelist of approved substances, with a primary focus on excluding those classified as carcinogenic, mutagenic, or reprotoxic (CMR).

Aims:

This project supports the development of Belgium’s initial whitelist of e-liquid ingredients. It analyzes substances reported under Directive 2014/40/EU by identifying high-risk ingredients and establishing scientifically grounded, transparent exclusion criteria. The ultimate objective is to enable a public health–oriented regulatory approach that is legally sound and scientifically defensible.

Methods:

Due to the impracticality of full toxicological assessments for all substances, a tiered approach is applied. Sciensano is conducting chemical characterization of complex ingredients and using screening methods such as in silico tools (VEGA QSAR, QSAR Toolbox), toxicological databases (PubChem, eChemPortal), and harmonized hazard classifications (CLP, IARC). Criteria for ingredient exclusion will be based on Belgian and EU legislation, expert input, and regulatory practices from other Member States. These criteria will be reviewed by the Belgian Superior Health Council, composed of independent scientific experts.

Results:

As the project is in its early phase, final results are pending. However, a preliminary list of CMR-classified substances is being compiled for removal. Initial screening uses established in silico tools and focuses on commonly used or highly concentrated ingredients to prioritize relevant targets. A structured process for data handling and toxic ingredient identification has been outlined to support hazard prioritization.

Conclusion:

This project will provide Belgium with a scientifically informed framework to regulate e-liquid ingredients via a whitelist. While the current work focuses on hazard identification and prioritization, further assessment—including exposure and in vitro studies—might be required for comprehensive evaluation. The project lays the groundwork for evidence-based policy, contributing to stronger consumer protection in the constantly evolving e-cigarette market.