Large and increasing numbers of chemicals are produced and used by modern society. Materials and products we use contain many known and unknown chemicals, some of which can pose hazards to human health and to the environment. Methods capable of mapping all hazardous substances present in materials and products are needed to support proper regulation in order to minimize risks for human and environmental health. There is a need to get an overview describing to which extent these methods have been used, if substances have successfully been identified and whether these identified substances are relevant in a regulatory perspective. This work aims to provide an overview of studies that have been done to date using NTS and SS to identify substances in articles, chemical products, and recycled materials and screen and assess the identified chemicals identified with high confidence (Schymanski levels 1 and 2) for regulatory relevance. This provides a basis for an evaluation of the applicability and efficiency of current NTS and SS methods for identifying substances relevant for regulatory actions.
Overall, 76 documents were initially retrieved and reviewed. Of these, 38 were selected for further review based on relevance and data availability. Identified chemicals and associated information was extracted from each of these studies. Of the final selected studies, 26 directly screened the product, 8 screened for chemical migrants from products, and 4 studies did both. Only 34 out of the 38 studies contained chemicals identified at high confidence level (Schymanski level 1 or 2). Of these, 19 used NTS, 11 SS, and 4 employed both methods. In total, more than 1,500 products were screened covering different product categories such as plastics, elastomers, chemical products/material related, paper/paperboard, textiles and wood. By far most studies looked at plastic products (>900 products), while the second biggest product category was textiles (>200 products). In total, nearly 3000 unique chemical entries were registered at varying confidence levels from which 1,700 were identified at Schymanski level 1 and 2. Of the latter, 28 substances are restricted under REACH, 4 are regulated as POPs with an additional 6 being proposed as POPs. Approximately 200 of the high confidence substances have a harmonized classification (CLH) under the CLP while 50 are included in the SVHC Candidate List. Finally, 62 of the identified chemicals have been prioritized as PMT/vPvM substances. In general, the compounds most frequently detected in each of the high level categories are compounds belonging to relevant types of compounds: antioxidants, plasticizers, pigments, long chain alkanes, etc. The elastomer, paper/paperboard and plastic + wood categories showed large similarities concerning the frequently detected compounds which may be a result of similar surface treatments, additives or modifications in itself or due to a combination of prevalence and bias.
The review highlighted the presence of restricted/hazardous chemicals even among the most frequently detected substances. Key obstacles encountered in this study included time-intensive data curation and lack of standardized workflows for NTS/SS studies making data interpretation/evaluation challenging. Differences in analytical techniques, sample preparation, and database limitations are well known sources of variability in results that can add additional uncertainty to these types of studies. Additionally, both false positives and negatives remain significant concerns, particularly in regulatory applications. Inconsistent usage of chemical identifiers also emerged as a significant challenge.
In summary, NTS and SS have shown potential as tools for identifying regulatory-relevant substances. However, they are currently more suited for early-warning screening due to methodological limitations. The report emphasizes the need for standardized workflows, enhanced QA/QC measures, and collaborative trials to improve comparability and reliability of findings. Future research should focus on integrating computational tools to prioritize chemical hazards and address gaps in regulatory databases. This report serves as a foundational resource for understanding the current capabilities and limitations of NTS and SS methods in regulatory applications, advocating for advancements to realize their full potential in chemical safety and environmental health.