A weight-of-evidence approach to assess chemicals: case study on the assessment of persistence of 4,6-substituted phenolic benzotriazoles in the environment

Brandt et al. Environ Sci Eur (2016) 28:4 DOI 10.1186/s12302-016-0072-y Open Access RESEARCH A weight‑of‑evidence approach to assess chemicals: case study on the assessment of persistence of 4,6‑substituted phenolic benzotriazoles in the environment Marc Brandt*, Eva Becker, Ulrich Jöhncke, Daniel Sättler and Christoph Schulte Abstract Background: One important purpose of the European REACH Regulation (EC No. 1907/2006) is to promote the use of alternative methods for assessment of hazards of substances in order to avoid animal testing. Experience with environmental hazard assessment under REACH shows that efficient alternative methods are needed in order to assess chemicals when standard test data are missing. One such assessment method is the weight-of-evidence (WoE) approach. In this study, the WoE approach was used to assess the persistence of certain phenolic benzotriazoles, a group of substances including also such of very high concern (SVHC). Results: For phenolic benzotriazoles, assessment of the environmental persistence is challenging as standard information, i.e. simulation tests on biodegradation are not available. Thus, the WoE approach was used: overall information resulting from many sources was considered, and individual uncertainties of each source analysed separately. In a second step, all information was aggregated giving an overall picture of persistence to assess the degradability of the phenolic benzotriazoles under consideration although the reliability of individual sources was incomplete. Conclusions: Overall, the evidence suggesting that phenolic benzotriazoles are very persistent in the environment is unambiguous. This was demonstrated by a WoE approach considering the prerequisites of REACH by combining several limited information sources. The combination enabled a clear overall assessment which can be reliably used for SVHC identification. Finally, it is recommended to include WoE approaches as an important tool in future environmental risk assessments. Keywords: Risk assessment, Weight-of-evidence approach, Persistence, Phenolic benzotriazoles, REACH, SVHC, Readacross, Monitoring studies, QSAR Background In the European Union, chemicals are subject to the chemicals legislation REACH (EC 1907/2006) [1]. Manufacturers and importers have to register substances to the European Chemicals Agency (ECHA) and provide the risk assessment as required by REACH. The authorities are responsible to evaluate certain selected substances and—if necessary—to propose and enforce additional *Correspondence: German Environment Agency, Section IV 2.3 “Chemicals”, Umweltbundesamt (UBA), Wörlitzer Platz 1, 06844 Dessau‑Roßlau, Germany regulatory actions like authorisation or restriction of chemicals and their uses. Of special interest are substances of very high concern (SVHC). With regard to the environment, SVHC mostly are substances that are identified as persistent, bioaccumulative and toxic (PBT substances) and substances that are very persistent and very bioaccumulative (vPvB substances). SVHC are identified under REACH in a formal process. A Member State or the ECHA needs to demonstrate that the criteria laid out in REACH Annex XIII are fulfilled (see Table 1). A main policy goal of REACH is “to ensure a high level of protection of human health and the environment, including the © 2016 Brandt et al. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Brandt et al. Environ Sci Eur (2016) 28:4 Page 2 of 14 Table 1 Criteria for assessment of PBT and vPvB properties according to REACH Annex XIII, number 1 PBT vPvB Persistence Screening criterion Not readily biodegradable Degradation half-lives (days) Water, marine >60 >60 Fresh water >40 >60 Marine sediment >180 >180 Fresh water sediment >120 >180 Soil >120 >180 Bioaccumulation Screening criterion Log Kow >4.5 BCF >2000 >5000 Toxicity NOEC <0.01 mg/l – CMR Endocrine active promotion of alternative methods for assessment of hazards of substances” (REACH Article 1). This article focuses on one specific alternative method for the assessment of hazards of substances, the weightof-evidence approach (WoE approach). In addition, some other alternative methods for prediction of chemical properties like read-across assessment or use of in silico methods are briefly described. Two reasons support the use of alternative assessment methods: alternative methods for hazard assessment are necessary, as animal testing should be avoided if possible. On the other hand, there is the problem that for specific situations reliable information needed for assessing the hazard potential of a substance is missed when only the established standard assessment schemes, which consist mostly of laboratory tests, are used. The latter leads to misjudgment of substances, which need to be identified as SVHC. To illustrate this point, a small number exercise can be employed: there is an obvious mismatch between the number of substances registered under REACH and the number of substances identified as PBT/ vPvB. Currently, 9032 substances (as of the 31.12.2015) are registered under REACH. However, there are only 22 substances (as of 3.12.2015) identified as PBT and/ or vPvB substances so far and not all of them have been registered. If all of these would have been registered, that would amount to 0.2 % of the registered substances. In a study by Strempel et al. [2], 94,483 substances of the European Inventory of Existing Commercial chemical Substances (EINECS register) were screened for PBT and vPvB properties. Based on their results, the authors estimate that approximately 3 % of all the substances in the register, i.e. 2930 substances, might be PBT/vPvB substances. In comparison to the 22 PBT/vPvB substances currently identified, this is a mismatch that can only partially be explained by the fact that the REACH registration has been in force for merely 9 years. In 2010, the review of the setup of procedures to identify SVHC concluded that these cannot ensure the policy goal of a sufficiently high level of protection. Therefore, in 2011 Annex XIII was amended in order to enable identification of SVHC according to the state of environmental science [3]. The amended Annex XIII strengthens the assessment by allowing additional endpoints indicating PBT properties (e.g. biomagnification) and different assessment strategies like the WoE approach. Up to now, there is not much experience in employing the WoE approach under REACH although this approach has been used in the past 60 years, especially in medicine, but also in toxicology (see for example [4]) and at least since the 19 (...truncated)