Environmental Safety

Environmental Fate of Bisphenol A

Environmental OECD Biodegradability Guidelines

Excerpted from OECD's Harmonized Integrated Hazard Classification System For Human Health and Environmental Effects of Chemical Substances

HARMONIZED SYSTEM FOR THE CLASSIFICATION OF CHEMICALS WHICH ARE HAZARDOUS FOR THE AQUATIC ENVIRONMENT

Rapid degradability

8. Environmental degradation may be biotic or abiotic (e.g. hydrolysis) and the criteria used reflect this fact (Annex I). Ready biodegradation can most easily be defined using the OECD biodegradability tests OECD Test Guideline 301 (A - F). A pass level in these tests can be considered as indicative of rapid degradation in most environments. These are freshwater tests and thus the use of the results from OECD Test Guideline 306 which is more suitable for marine environments has also been included. Where such data are not available, a BOD(5 days)/COD ratio >0.5 is considered as indicative of rapid degradation.

9. Abiotic degradation such as hydrolysis, primary degradation, both abiotic and biotic, degradation in non-aquatic media and proven rapid degradation in the environment may all be considered in defining rapid degradability. Special guidance on data interpretation will be provided in the Guidance Document.

20. Substances that rapidly degrade can be quickly removed from the environment. While effects can occur, particularly in the event of a spillage or accident, they will be localised and of short duration. The absence of rapid degradation in the environment can mean that a substance in the water has the potential to exert toxicity over a wide temporal and spatial scale. One way of demonstrating rapid degradation utilises the biodegradation screening tests designed to determine whether a substance is `readily biodegradable'. Thus a substance which passes this screening test is one that is likely to biodegrade `rapidly' in the aquatic environment, and is thus unlikely to be persistent. However, a fail in the screening test does not necessarily mean that the substance will not degrade rapidly in the environment. Thus a further criterion was added which would allow the use of data to show that the substance did actually degrade biotically or abiotically in the aquatic environment by >70% in 28 days. Thus, if degradation could be demonstrated under environmentally realistic conditions, then the definition of `rapid degradability' would have been met. Many degradation data are available in the form of degradation half-lives and these can also be used in defining rapid degradation. Details regarding the interpretation of these data will be further elaborated in the Guidance Document. Some tests measure the ultimate biodegradation of the substance, i.e. full mineralisation is achieved. Primary biodegradation would not normally qualify in the assessment of rapid degradability unless it can be demonstrated that the degradation products do not fulfil the criteria for classification as hazardous to the aquatic environment.