Accidental discharge of brodifacoum baits in a tidal marine environment: A New Zealand case study

Brodifacoum is a second-generation anticoagulant used worldwide in bait formulations for commensal rodent control, and in some countries for field control of vertebrate pests. As the result of a New Zealand road transport accident in May 2001, a tidal marine environment was exposed to up to 18 tonnes of rodent bait (c. 360g of brodifacoum) as a point source, which was an unprecedented incident. Immediate monitoring of marine biota, water and sediment was undertaken. This was particularly important because the area was used for human food collection. No local mortalities of marine birds or mammals were attributed to the spill.

Contamination of the marine environment was localized in about a 110m2 area. The decline of brodifacoum residues in algal-grazing and filter-feeding marine invertebrates over a three-year period is described. A ban by New Zealand authorities on the collection of shellfish from the area was lifted in May 2004. The decline of brodifacoum residues in various sample media was probably due to a combination of physical dispersal (rather than chemical degradation) of brodifacoum in the highly dynamic tidal marine environment, and a previously undescribed and relatively long retention (half-life) of brodifacoum in marine mollusks.

Author Primus, T.
Date 2004-10-19
Year 2004
Secondary title 2nd National Invasive Rodent Summit
Place published Fort Collins
Publisher National Wildlife Research Centre
Pages 17
Control method Baiting
Region NZ