Use of biodegradation data in chemical assessment

Abstract

Biodegradation is an important removal mechanism for consumer product chemicals released in large volumes to aquatic and terrestrial environments. It results in a decrease in the mass or load of chemicals present in the environment and is key in preventing accumulation and persistence of chemicals. Although biodegradation is an important process in minimizing potentially adverse impacts on environmental systems, it has not been traditionally considered quantitatively in environmental assessments. Efforts to use such data have principally focused on either wholly qualitative evaluations of a material's biodegradation properties (e.g., “fast” or “slow”), or rigorous quantitative models to predict exposure concentrations in particular settings. This paper outlines an alternative approach which provides a semi-quantitative analysis combining biodegradation rate data with an assessment of environmental exposure. The approach is a generic one that relates biodegradation half-lives to rates of transport and residence times in specific environmental compartments (e.g., agricultural soil, rivers). It establishes the kinetic criteria needed to make biodegradation a “practically significant” removal mechanism in a given environmental compartment. It is broadly applicable to chemicals which exhibit pseudo first order biodegradation kinetics at realistic environmental concentrations.