C8- and C9-Alkylphenols and Ethoxylates: II. Assessment of Environmental Persistence and Bioaccumulation Potential

ABSTRACT

C8- and C9-alkylphenols and their ethoxylates (APE) are widely used commercial products mainly used in industrial applications, in the formulation of crop protection chemicals, and in industrial and household cleaners. Recent regulatory focus on these compounds has included an assessment of their potential to meet criteria for persistent, bioaccumulative, and toxic compounds (PBT). To fully evaluate either the relative persistence or bioaccumulation potential of any APE, degradation intermediates and metabolic by-products of these compounds should also be considered. To facilitate the evaluation of the ultimate fate of APE in the environment, a review of the degradation pathways and identification of degradation intermediates was performed (part I of a two-part series). In part II of this series, the relative persistence of APE as indicated by degradation half-lives was examined based on a review of abiotic and biological degradation data. To assess the bioaccumulation potential of APE, the relevant literature was also reviewed. The available data for C8- and C9-APE show that the commercial products and their degradation intermediates do not meet any national or international criteria for identifying these compounds as PBT substances.

Key Words:

• alkylphenols
• ether carboxylates
• biodegradation
• bioconcentration
• surfactants
• fate

ACKNOWLEDGMENT

This work was sponsored by the Alkylphenols and Ethoxylates Research Council, Washington, DC, USA.

Notes

¹Note that consideration of the 10-day window for assessing ready biodegradability is based on guidance provided by the OECD (1996). Recent guidance according to the EU Detergent Directive indicates that the 10-day window may be inappropriate for assessing the biodegradability of surfactant mixtures (CSTEE 1999; Richterich and Steber 2001).

²In order to be considered “readily” biodegradable, ready test results for a compound must achieve > 60% degradation within 28 days and reach the 60% level within 10-days of achieving the initial 10% (the 10-day window). A test result for a compound achieving > 20% but < 60% degradation, or reaching 60%, but not meeting the 10-day window are designated “inherently” biodegradable.

^a According to the USEPA (2002b), ready test results achieving > 60% degradation (10-day window not considered) can be extrapolated to half-lives in the aquatic compartment of 5 days. Based on guidance provided in the Technical Guidance Document (EC 2003), ready test results achieving > 60% degradation indicate half-lives of 15 days if the 10-day window is met and 50 days if not met.

^b Half-lives recalculated by Staples et al. (2001).