Modeling explicitly and mechanistically median lethal concentration as a function of time for risk assessment.

A mechanistic model that explains how toxic effects depend on the duration of exposure has been developed. Derived from the dynamic energy budget (DEB)tox model, it expresses the hazard rate as a function of the toxic concentration in the organism. Using linear approximations in accordance with the general simplifications made in DEBtox, the concentration that induces x% of lethality (LCx) and in particular the lethal concentration 50% (LC50) are expressed explicitly as functions of time. Only three parameters are required: an asymptotic effect concentration, a time constant, and an effect velocity. More sophisticated (but still analytic) models are possible, describing more complex toxicity patterns such as an increase of sensitivity with time or, conversely, an adaptation. These models can be fitted to the common and widespread LC50 endpoints available from the literature for various aquatic species and chemicals. The interpretation of the values assigned to the parameters will help explain the toxicity processes and standardize toxicity values from different sources for comparisons.

Analysis of the ecotoxicity data submitted within the framework of the REACH Regulation. Part 1. General overview and data availability for the first registration deadline.

REACH(1) entered into force in June 2007 and has hence been operational for six years. With the first registration deadline in November 2010, the European Chemicals Agency (ECHA(2)) has received a large amount of scientific and administrative information related to chemical substances. In order to understand what type of data on ecotoxicity endpoints was submitted under the REACH framework a detailed analysis of the availability and content of relevant information was performed. To avoid unnecessary testing, the REACH Regulation provides registrants with the possibility to build testing strategies and to adopt the standard information requirements based on the specific conditions listed in the regulation. The types of information submitted by registrants to fulfil data requirements for aquatic, sediment and terrestrial toxicity endpoints were analysed. The REACH database analysis confirms large differences in the availability of experimental aquatic versus sediment and soil ecotoxicity data. Information requirements on aquatic organisms are mainly covered by experimental data, while those for sediment and soil are mostly waived.

Analysis of the ecotoxicity data submitted within the framework of the REACH Regulation. Part 2. Experimental aquatic toxicity assays.

This paper summarises the aquatic ecotoxicity data submitted in the REACH(1) registration dossiers and disseminated by the European Chemicals Agency (ECHA(2)). The analysis describes both the guidelines and the species mostly used by registrants. Non-OECD guidelines have been extensively used, in particular in covering of fish and aquatic invertebrate studies, but the main concern is that in 22-36% of the cases, depending on the endpoint, no information on the methodological approach and potential equivalences to test guidelines has been provided. As expected, most studies were conducted with those species typically used in laboratory ecotoxicity testing; nevertheless, the database provides a broad range of available species, covering the most relevant taxonomic groups for both freshwater and marine systems, although most are just occasionally used. This species diversity is essential for higher tier testing strategies, including the use of Species Sensitivity Distribution approaches. The assessment suggests that collecting available information has been the main approach used by registrants to fulfil their REACH information requirements for this first REACH registration deadline. Many studies are disclosed for the first time, and all are available through searchable web tools.

Analysis of the ecotoxicity data submitted within the framework of the REACH Regulation: part 4. Experimental terrestrial toxicity assays.

This paper summarises the terrestrial ecotoxicity data submitted in the REACH registration dossiers and disseminated by ECHA. The analysis describes both the guidelines and the test species mostly used by registrants. REACH information requirements in relation to the effects on terrestrial organisms encompass three trophic levels; invertebrates, plants and micro-organisms, and the study of both long and short-term exposure. The results observed for soil invertebrates showed that on one hand there was a clear prevalence for testing on the species recommended by the standard test guidelines. On the other, the reporting included a large variety of species from very different families, demonstrating the feasibility for conducting toxicity tests on a number of relevant groups e.g. for species sensitivity distribution approaches. Standard toxicity testing with terrestrial plants under REACH follows a different approach and requires simultaneous testing on several species, using the same test conditions, adapted to each species, if needed. The test methods used to conduct the studies were only reported for 30% of cases. The most extensively reported test guidelines for terrestrial plants were OECD 208, ISO 11269-1 and ISO 11269-1. Information requirements for soil micro-organisms under REACH are related to the analysis of functional endpoints instead of on species or taxa. As recommended in REACH, OECD 216 and OECD 217 were the most often used test methods for soil micro-organisms. But overall, the test method was reported for only about 40% of the experimental studies. Moreover, it is noted that information on potential effects on soil micro-organisms is available for a limited number of REACH registered substances. The assessment suggests that providing waiving justifications and collecting available information, which in many cases might be well used for covering standard REACH data requirements, have been the main approaches used by registrants for the first REACH registration deadline.

Analysis of the ecotoxicity data submitted within the framework of the REACH Regulation. Part 3. Experimental sediment toxicity assays.

For the first REACH registration deadline, companies have submitted registrations with relevant hazard and exposure information for substances at the highest tonnage level (above 1000 tonnes per year). At this tonnage level, information on the long-term toxicity of a substance to sediment organisms is required. There are a number of available test guidelines developed and accepted by various national/international organisations, which can be used to investigate long-term toxicity to sediment organisms. However instead of testing, registrants may also use other options to address toxicity to sediment organisms, e.g. weight of evidence approach, grouping of substances and read-across approaches, as well as substance-tailored exposure-driven testing. The current analysis of the data provided in ECHA database focuses on the test methods applied and the test organisms used in the experimental studies to assess long-term toxicity to sediment organisms. The main guidelines used for the testing of substances registered under REACH are the OECD guidelines and OSPAR Protocols on Methods for the Testing of Chemicals used in the Offshore Oil Industry: "Part A: A Sediment Bioassay using an Amphipod Corophium sp." explaining why one of the mostly used test organisms is the marine amphipod Corophium sp. In total, testing results with at least 40 species from seven phyla are provided in the database. However, it can be concluded that the ECHA database does not contain a high enough number of available experimental data on toxicity to sediment organisms for it to be used extensively by the scientific community (e.g. for development of non-testing methods to predict hazards to sediment organisms).