In the current study, the EC SSbD framework was applied to compare two different types of flame retardants (FR): phosphinate-based (PFR) against brominated flame retardants (BFR) with regard to their safety and sustainability performance. One of the main applications of FRs is their use in plastics for electronic devices. More specifically, we evaluated the safety and environmental sustainability of aluminum diethyl phosphinate (DEPAL) based FR compared to decabromodiphenyl ethane (DBDPE) based FR used in polyamides for household electronic devices, such as plugs and connectors. DBDPE was chosen as a model BFR of additive nature (vs. reactive or polymeric) although it is not a widely used in polyamides. Despite findings of adverse effects on human health or the environment for some BFR, they have maintained a significant share of the FR market. Therefore, alternative flame retardant solutions are investigated and proposed, such as DEPAL, which is classified as an organophosphorus FR. The environmental sustainability assessment (Step 4 of SSbD) has already been performed in a previous case study (Maga et al., 2024), using a different BFR. The present paper includes the full SSbD assessment of these FR, including their synergists, except for the socioeconomic analysis (Step 5), which is considered optional.
For the execution of SSbD assessment, the SSbD toolbox, developed within the European Partnership for the assessment of risks from chemicals (PARC), was used. The PARC SSbD toolbox is designed to be an integrative tool for the implementation of the EC SSbD framework. It offers a comprehensive inventory of tools (e.g., models, methods, algorithms) for safety and sustainability assessment, while it also provides an interactive interface by functionally linking the different types of tools. The PARC SSbD toolbox takes into account the different innovation stages for developing a chemical or material into a final product. Thus, it integrates the five steps of the EC framework into the five innovation stages, as described by the Cooper’s stage-gate model. In the context of this case study, we explored the applicability of different computational tools included in the PARC SSbD toolbox for the types of FR mentioned earlier. We investigated the use of predictive data by Quantitative Structure Activity Relationship (QSAR) and Quantitative Structure Property Relationship (QSPR) models, as well as available data for performing the different SSbD steps.
Step 1 – Hazard assessment: in the hazard assessment of the FR chemicals both in-silico and experimental data were applied. For the in-silico approach several QSAR tools, including VEGA, OECD QSAR toolbox, Danish QSAR Database models and StopTox, were employed to predict their respective hazard properties. In cases of multiple predictions from one endpoint, the majority of the predictions were considered as the final result. Predictions that were outside the applicability domain of the models were excluded from the assessment. The QSAR models were not applicable to all the types of FR, such as DEPAL or its phosphinate-based synergist, due to their chemical structure and type (e.g., inorganic compounds). However, experimental data were available for most of the chemicals. Step 2 – Human health and safety aspects in the production and processing phase: in this step the occupational health and environmental risks of the chemicals were assessed. The tool employed for the occupational exposure and risk assessment was ECETOC TRA worker tool, whereas the multimedia model of the INTEGRA tool was applied to estimate the environmental risk in the production and processing phase.
Step 3 – Human health and environmental aspects in the final application phase: the INTEGRA multimedia model was also utilized for assessing the environmental risks in the final application phase. For the consumer exposure, the relevant exposure scenario identified for the assessment was the exposure to household dust due to the release of the FR from the product’s surface to atmosphere. For the assessment, the dust model of INTEGRA was used to estimate the respective consumer exposure concentration. Step 4 – Environmental sustainability assessment: a life cycle assessment (LCA) was performed in Step 4 to examine the environmental impacts of both FR systems. A cradle-to-grave assessment was carried out as the one described in Maga et al. (2024). Regarding the modeling part, the SimaPro LCA software was used, along with the Ecoinvent LCA database.
Overall, most of the chemicals under study were outside of the applicability domain of the QSAR/QSPR models available in the PARC SSbD toolbox. As a result, the hazard assessment step could not be performed with the application of in silico tools. Moreover, the exposure assessment steps could not be carried out using only predictive data. In the assessment with experimental data, modelling assumptions were applied to address data gaps that could not be filled in. In conclusion, the phosphinate-based FR system demonstrated a better SSbD profile than the brominated-based FR, resulting in higher SSbD scores. The outcomes of this case study have provided valuable insights into the development and the enhancement of the PARC SSbD toolbox, indicating both benefits and limitations of its current functionalities.