The controversial possum control poison 1080 has no negative effects on surface or ground water, a study by Niwa researchers has found.
The research looked at what happens to 1080, used throughout New Zealand to control pests that spread bovine tuberculosis, when it leaches from uneaten cereal baits.
It found more than 99 percent of the toxin-laden rainwater went straight into the soil, where it was quickly broken down into harmless metabolites, rather than flowing overland into streams.
In addition, it found the level of 1080 in soil water from scattered, individual baits during normal possum control operations never exceeded a third of the Ministry of Health drinking water standard and may not be detectable.
"From these results, we can conclude that the effects of 1080 leaching from baits into soil water and stream water are highly, highly unlikely to have any adverse effects on water quality," said freshwater ecologist Dr Alastair Suren, who led a series of field trials in rugged West Coast terrain.
The study was carried out by Niwa on behalf of the Animal Health Board, the body responsible for the tuberculosis eradication programme.
The use of 1080 has been opposed by some hunters and animal rights activists.
NZN