Enhanced ready biodegradability screening tests for the evaluation of potential PBT substances.

In persistence assessment enhanced ready biodegradation tests (eRBT) are aimed to close the gap between screening tests and complex simulation tests. However, only few data from these tests are available and neither guidance on the design and interpretation of eRBTs, nor suitable validity criteria have been established so far. In a practical testing programme 5 compounds with controversial degradation data have been tested in 4 test series including prolongation to 60 days and use of different inocula (activated sludge, final effluent from a STP), flask sizes, and endpoints (CO2, O2, DOC). The drug ibuprofen and the intermediate 4-fluorophenol were biodegraded by >60% within 28 days within a 10-day-window and therefore are considered as readily biodegradable and in conclusion fulfilling the criteria for "not persistent". The mean mineralization of the pesticide synergist piperonylbutoxide and the antioxidant octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate achieved 20%-50% (="potentially P"). The mineralization of the cosmetic ingredient cis-13-docosenonamide (Erucamide) was between 36%-64% after 60 days with activated sludge and 21% with the effluent from the STP. Diethylene glycol reached the pass level of 60% mineralization within 28 days in all test series without always meeting the 10-day window, and thus proved to be a suitable reference substance for eRBTs. Based on the results of the study several recommendations for the test design, the evaluation and the interpretation of eRBTs are made. However, a broader data set is required and further enhancements such as the quality and amount of the inoculum should also be considered in future 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.

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.

The Dessau workshop on bioaccumulation: state of the art, challenges and regulatory implications.

Bioaccumulation plays a vital role in understanding the fate of a substance in the environment and is key to the regulation of chemicals in several jurisdictions. The current assessment approaches commonly use the octanol-water partition coefficient (log KOW) as an indicator for bioaccumulation and the bioconcentration factor (BCF) as a standard criterion to identify bioaccumulative substances show limitations. The log KOW does not take into account active transport phenomena or special structural properties (e.g., amphiphilic substances or dissociating substances) and therefore additional screening criteria are required. Regulatory BCF studies are so far restricted to fish and uptake through the gills. Studies on (terrestrial) air-breathing organisms are missing. Though there are alternative tests such as the dietary exposure bioaccumulation fish test described in the recently revised OECD test guideline 305, it still remains unclear how to deal with results of alternative tests in regulatory decision-making processes. A substantial number of bioaccumulation fish tests are required in regulation. The development of improved test systems following the 3R principles, namely to replace, reduce and refine animal testing, is thus required. All these aspects stress the importance to further develop the assessment of bioaccumulation. The Dessau Workshop on Bioaccumulation which was held from June 26th to 27th 2014, in Dessau, Germany, provided a comprehensive overview of the state of the art of bioaccumulation assessment, provided insights into the problems and challenges addressed by the regulatory authorities and described new research concepts and their regulatory implications. The event was organised by UBA (Dessau, Germany) and Fraunhofer IME (Schmallenberg, Germany). About 50 participants from industry, regulatory bodies and academia listened to 14 lectures on selected topics and joined the plenary discussions.

Problems faced when evaluating the bioaccumulation potential of substances under REACH.

The identification and regulation of substances that combine persistence, bioaccumulation potential, and toxicity ("PBT" substances) is one central aspect of the European chemical legislation REACH (Registration, Evaluation, Authorisation, and Restriction of Chemicals), because these substances may elicit adverse long-term effects after release to the environment. The determination of a substance that has persistence, bioaccumulation potential, and toxicity is based on a set of distinct cutoff criteria identified in Annex XIII of the REACH regulation. Regarding the bioaccumulation potential, the evaluation is focused on the substance's bioconcentration factor as single decisive criterion. In addition, the REACH guidelines provide a selection of standardized test procedures for measuring bioconcentration factor and guidance in appraising test results. However, alternative test results like bioaccumulation factors and biomagnification as well as additional indications for a bioaccumulation potential such as trophic magnification are only allowed for supporting evidence. The currently used test systems with aquatic exposure have been demonstrated to generate reliable results for the majority of neutral, lipophilic organic substances, which facilitate clear decision-making by means of the crucial bioconcentration factor cutoff criteria of Annex XIII. However, certain substance groups such as highly hydrophobic organic substances and amphiphilic and nonlipophilic compounds are difficult to evaluate with common test strategies due to inappropriate test systems or accumulation mechanisms not based on lipophilicity. Recent scientific progress has already been made to establish alternative test systems and to refine the bioaccumulation assessment by consideration of additive accumulation mechanisms and indications. This article gives an overview on actual shortcomings in the current bioaccumulation assessment under REACH and also provides suggestions for a refinement of evaluation.