Comparison of Small Molecule Biotransformation Half-Lives between Activated Sludge and Soil: Opportunities for Read-Across?

Compartment-specific
degradation half-lives are essential pieces
of information in the regulatory risk assessment of synthetic chemicals.
However, their measurement according to regulatory testing guidelines
is laborious and costly. Despite the obvious ecological and economic
benefits of knowing environmental degradability as early as possible,
its consideration in the early phases of rational chemical design
is therefore challenging. Here, we explore the possibility to use
half-lives determined in highly time- and work-efficient biotransformation
experiments with activated sludge and mixtures of chemicals to predict
soil half-lives from regulatory simulation studies. We experimentally
determined half-lives for 52 structurally diverse agrochemical active
ingredients in batch reactors with three concentrations of the same
activated sludge. We then developed bi- and multivariate models for
predicting half-lives in soil by regressing the experimentally determined
half-lives in activated sludge against average soil half-lives of
the same chemicals extracted from regulatory data. The models differed
in how we accounted for sorption-related bioavailability differences
in soil and activated sludge. The best-performing models exhibited
good coefficients of determination (R2 of around 0.8) and low average errors (