The effects of river flooding on dioxin and PCBs in beef

•Concentrations of dioxins and PCBs were higher in soil and grass from flood-prone farms.•The beef samples from flood-prone farms had higher total TEQs.•The first such controlled investigation.•Flooding is a contaminant transfer mechanism to cattle raised on river catchments.•Contamination is likely to be a result of legacy sources.

In 2008–2010, samples of meat from 40 beef cattle, along with grass, soil and commercial feed, taken from ten matched pairs of flood-prone and control farms, were analysed for PCDD/Fs and PCBs. Concentrations were higher in soil and grass from flood-prone farms. The beef samples from flood-prone farms had total TEQ levels about 20% higher than on control farms. A majority of flood-prone farms (7/10) had higher median levels in beef than on the corresponding control farm. This first controlled investigation into PCDD/F and PCB contamination in beef produced on flood-prone land, presents robust evidence that flooding is a contaminant transfer mechanism to cattle raised on river catchments with a history of urbanisation and industrialisation. PCDD/F and PCB sources in these river systems are likely to be a result of the legacy of contamination from previous industrialisation, as well as more recent combustion activity or pollution events.

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