Water-Accommodated Fractions, or WAFS, are recommended by OECD GD 23 “Guidance Document on Aqueous-Phase Aquatic Toxicity Testing of Difficult Test Chemicals” for use with ecotoxicology studies for chemical substances of Unknown or Variable Composition, Complex Reaction Products and Biological Materials (UVCBs).
Biologist Melissa Staggs and colleagues from the Smithers Wareham aquatic ecotoxicology laboratory
found that as UVCBs are highly variable, biological responses to exposure are not always proportional to the exposure concentration.
Using exposures to Daphnia
, the team was able to show that despite WAFs being diluted over four orders of magnitude, the measured concentration of three UVCB components varied by only a factor of three. This was supported by the shallow response curves from the % inhibition seen in the experimental systems. Preparation of individual WAFs are also challenging due to the difficulty in measuring small amounts of UVCB for the lower concentrations.
To learn more on this topic, watch an overview of Melissa's SETAC Europe poster
presentation or download the full poster.