Consolidating exposure scenario information for mixtures--experiences and challenges.

Abstract

The requirements of the European Union Regulation on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), including the preparation of exposure scenarios for the communication of safe use, are focused on single substances. Since the chemical products used at workplaces are typically mixtures, it is important to ensure that accurate information is available regarding their safe use. The focus of the present study was on the methods for consolidating (combining) the information presented in the exposure scenarios of the individual components of a mixture. We tested the applicability and comparability of three methods for consolidating the exposure scenario information on six real products, focusing on occupational exposure. Two of the reviewed methods were based on the identification of the critical components that determine the health effects and risk management of the product, and one was based on the selection of the most stringent risk management measures presented in the exposure scenarios of the components. The differences in the critical components recognised by the two critical component-based methods revealed limitations in both of the methods. The quality and comprehensiveness of the consolidated scenarios produced by the two methods were generally of the same level, depended directly on the content of the exposure scenarios of the critical components. Choosing the most stringent risk management measures improved the comprehensiveness of the scenarios. All of the examined methods run the risk of communicating over-precautionary measures if the concentration of the components determining the level of protection is not taken into consideration. Of the three methods considered, we recommend the selection of the most stringent operational conditions and risk management measures as a conservative default approach for consolidating exposure scenario information. If a critical component-based approach is used, checking the adequacy of the consolidated scenario for the other components of the mixture is recommended. With all of the methods, further modification of the consolidated scenario may be necessary to achieve the intended level of protection.