NIWA says there is no basis to fears that aerial drops of 1080 are contaminating waterways on the West Coast.
The Crown Research Institute says it tested many samples from an unnamed stream near Reefton in August last year.
The National Institute of Water and Atmospheric Research says it sub-contracted Landcare Research to do the tests which were carried out before and after an aerial drop of 1080, and also before and after rainfall.
NIWA says 1080 was detected in one sample, with a concentration of 0.1 micrograms per litre.
The Ministry of Health's drinking water standards stipulate that the amount of 1080 must not exceed 3.5 micrograms per litre.
NIWA is confident the research reflects the situation throughout New across the country.
However, West Coast residents against the use of 1080 say they are not convinced the testing was extensive enough.