Characterising the hazard of highly persistent substances that exhibit low levels of bioaccumulation

The UK (Anglo Welsh) Environment Agency’s Chief Scientist’s Group published a key report that shed light on the environmental assessment of highly persistent chemicals. This research is pivotal as it explores the intricacies of estimating the environmental concentrations of compounds that persist in ecosystems for extended periods.

Persistent chemicals, such as per- and polyfluorinated alkyl substances (PFAS), pose substantial potential risks due to their prolonged presence in the environment. Despite limited accumulation in organisms, they can travel over vast distances, raising concerns about their impact on distant ecosystems.

The report examines PFAS substances such as PFHxA and GEN-X, which are well-known for their long-lasting nature. The researchers sought to examine the environmental fate and distribution and investigate alternate assessment approaches, using a conventional exposure model and application of a ‘time to steady-state’ approach.

Key findings suggest that the current quantitative approach to risk assessment at a local and regional scale appears to be equally appropriate for highly persistent substances as for non-persistent substances. In addition, time to steady-state can also be calculated at the global scale from standard regulatory model outputs, and this could be a useful metric for decision-making.  Uncertainties remain with the use of a quantitative risk assessment approach due to the length of time these highly persistent chemicals remain in the environment. The research recommends adopting a more cautious assessment approach or a hazard-based approach. It is considered essential to differentiate between chemicals that reach a steady-state within a few years and those that have much longer times to steady-state.

This report was conducted by Vitis Regulatory (as PFA before our name change to Vitis) for the Environment Agency’s Chief Scientist’s Group.