Workshop Report 24

Executive Summary

Many chemical regulatory schemes exist around the world that contain hazard-based criteria to identify and prioritise persistent, bioaccumulative and toxic (PBT), or very persistent very bioaccumulative (vPvB) chemicals. These are chemicals that have the potential to persist in the environment, accumulate within the tissue of living organisms and, in the case of chemicals categorised as PBTs, show adverse effects following long-term exposure (ECETOC, 2005).

This two-day workshop, co-sponsored by the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) and the CEFIC ECO 11 LRI project, and co-organised by representatives from ECETOC, Industry, the Federal Environment Agency of Germany (UBA) and the Environment Agency (EA) of England and Wales, took place at Les Salons France-Amérique, Paris, France on the 6th and 7th November 2012. This was a follow up to the 2007 “Biodegradation and Persistence” Holmes Chapel workshop co-hosted by ECETOC and the Environment Agency of England and Wales to assess areas of research required to help develop the scientific understanding of factors that affect the persistence of chemicals in the environment. The 45 attendees, from academia, regulatory agencies and industry, discussed the challenges and uncertainty faced with persistency assessments at the screening and confirmatory testing levels.

The primary aims of the 2012 workshop were to:


a)Identify whether / how the programmes initiated as a consequence of the Holmes Chapel Workshop have helped further the understanding of biodegradation / persistence related issues, b)Identify and prioritise key areas for further future research.

The presentations and discussions clearly indicated that the knowledge and science-base were moving forward within the field of persistence assessment. Significant developments include: the ECETOC and UBA activities to define and characterise extractable and non-extractable residues (NERs) formed in soil and sediment, the CEFIC funded work to understand the importance of biomass concentration and diversity within screening assessments for biodegradability, and the inclusion of more ecological realism and relevance within persistency assessments through the inclusion of light, natural waters and assessing adaptation potential and biodegradation outcome over time.

These scientific advancements at the screening and confirmatory level of persistence assessment were helping to (i) increase the body of data and experience for stakeholders (ii) address some uncertainties in persistence assessment and (iii) identify the key research needs that still need to be addressed to achieve a consensus position. The syndicate sessions identified themes for future research and development including:

  • Convening an OECD Expert Working Group to consolidate and update the ready biodegradability tests (RBTs) to reflect (i) the availability of new instrumentation with increased analytical sensitivity (ii) the use of tests with combined analytes (e.g. biochemical oxygen demand (BOD) and carbon dioxide evolution), and (iii) the need to screen for biodegradability in water-sediment systems.
  • Assessing the influence that temperature has on rates of biodegradability in aquatic and aquatic-sediment habitats and, consequently, the need for temperature extrapolation.
  • Assessing the ecological significance of adaptation and developing appropriate test methods and guidance accordingly.
  • Developing and validating models to predict non-extractable residue formation and guidance on how to assess the risks posed by NERs over time.
  • Benchmarking the microbiological and kinetic performance of the OECD 314, 308, 309 and enhanced biomass tests using appropriate reference chemicals.
  • Developing and validating tools and guidance to predict and assess the formation of transformation products in biodegradation studies.
  • Clarifying and resolving the test-based and model-based issues associated with the persistence assessment of complex substances.
  • Investigating the value of genetic sequencing procedures in determining differences / similarities in inocula to compare the relevance of laboratory inocula with the field situation.