To date, brodifacoum residues have not been detected in water bodies following any aerial baiting operations—not surprising, given that brodifacoum has very low solubility in water.
The baiting operation will be conducted to avoid bait going into the lagoon and minimise the entry of baits into the ocean.
What we already know, fresh water
From other aerial baiting operations, we know that there is a very low chance of any streams and other water bodies on Lord Howe Island containing detectable levels of brodifacoum, much less biologically harmful concentrations, as a result of the eradication.
Because brodifacoum has very low solubility in water and binds strongly to soils it is unlikely to get washed into the marine environment. Any baits entering streams or other water bodies sink, and disintegrate, usually within a few hours, depending on turbulence and rate of flow. The minute amount of brodifacoum in the bait (20 parts per million) settles in the sediment where it binds to organic material and breaks down.
Brodifacoum binds strongly to soil particles, where it is broken down by soil micro-organisms to its base components, carbon dioxide and water. While the cereal bait pellets disintegrate and disappear within 100 days or so, the toxin itself takes longer to break down but by this stage the concentration is so low that it poses no risk to humans or wildlife. Laboratory studies have shown that brodifacoum is effectively immobile (i.e. not leached) in the soil.
Nonetheless, water samples will be collected at various intervals after the baiting and analysed by an independent laboratory to reassure residents and tourists that the water (along with locally produced milk and locally caught fish) is not contaminated.
In the marine environment, outside the lagoon
Outside the lagoon, any baits that might enter the ocean will be exposed to wave action and strong currents resulting in rapid breakdown and dispersal. This, together with the high dilution factor, and the fact that brodifacoum has very low solubility in salt water, means that the potential risk to marine organisms is very low.
In the marine environment, within the lagoon
Within the lagoon, the physical breakdown of baits would not be as rapid, so entry of baits into the lagoon will be prevented by hand distribution of bait, rather than aerial distribution, along the accessible shoreline of the lagoon. As there is very low risk of brodifacoum being at detectable levels in the streams, any water entering the ocean or lagoon is unlikely to carry detectable levels of brodifacoum.
Fact Sheet Brodifacoum – is it the best choice? PDF 774 KB