The REACH regulation requires EU manufacturers and importers of substances to register information on the hazard and risk of their substances with the European Chemicals Agency (ECHA). Risk management of the substances is based on the provided information. It is known that conclusions on hazard and risk are influenced by expert judgements as well as potential conflict of interests. Thus, it is important that hazard and risk assessments are transparent and can be evaluated by a third party. The aim of this study is to scrutinize the transparency, i.e. the accessibility and comprehensibility, of information on substances registered under REACH. Data on repeated dose toxicity and hazard assessment conclusions were extracted for 60 substances from the REACH registration database available on the ECHA website. The data were compiled in a database for systematically evaluating the transparency of information related to the conclusions on hazard or risk. In addition, chemical safety reports (CSR) were requested from ECHA for five substances. The transparency of information on the hazard and risk of substances was found to be limited for several reasons. First, certain information was removed due to confidentiality and certain fields were not published because they could contain confidential information although the information had not been claimed confidential. Also, the extent to which registrants reported information varied, and the presentation of some data and certain terminology required further clarification. In addition, the data source for the majority of the key and supporting studies could not be identified due to confidentiality. Since registrants are only required to summarise studies, it cannot be verified whether all relevant information from non-public industry reports have been reported. Lastly, certain information related to the hazard and risk assessment were only reported in the CSR which is only available upon request; a time-consuming and work-intensive process. As information on registered chemicals is currently provided to the public, it is difficult to follow steps that are undertaken in the hazard and risk assessment. This limits the possibility for a third party to evaluate the assessment.

The goal of identifying hazardous chemicals registered under the Registration, Evaluation, Authorization and restriction of CHemicals (REACH) Regulation and taking appropriate risk management measures relies on robust data registrations. However, the current procedures for European chemical manufacturers and importers to evaluate data under REACH neither support systematic evaluations of data nor transparently communicate these assessments. The aim of this study was to explore how using a data evaluation method with predefined criteria for reliability and establishing principles for assigning reliability categories could contribute to more structured and transparent evaluations under REACH. In total, 20 peer-reviewed studies for 15 substances registered under REACH were selected for an in-depth evaluation of reliability with the SciRAP tool. The results show that using a method for study evaluation, with clear criteria for assessing reliability and assigning studies to reliability categories, contributes to more structured and transparent reliability evaluations. Consequently, it is recommended to implement a method for evaluating data under REACH with predefined criteria and fields for documenting and justifying the assessments to increase consistency of data evaluations and transparency.

This study highlights that the procedures for evaluating data under REACH and reporting these evaluations are neither systematic nor transparent.

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This is a call for action to scientific journals to introduce reporting requirements for toxicity and ecotoxicity studies. Such reporting requirements will support the use of peer‐reviewed research studies in regulatory decision‐making. Moreover, this could improve the reliability and reproducibility of published studies in general and make better use of the resources spent in research.