A Canterbury toxicology professor is supporting a call for the Environmental Protection Authority to immediately reassess the use of the pesticide chlorpyrifos.
The Pesticide Action Network says chlorpyrifos, which new research from Otago University found in 87% of South Island streams sampled, can interfere with brain development in an unborn foetus and newborn babies.
Professor Ian Shaw says although levels of chlorpyrifos weren't alarming, he is worried about what they could do when combined with traces of previously banned pesticides still found in streams.
The pesticide was given approval for use in June this year with restrictions.
Professor Shaw says the authority should reassess allowing the use of chlorpyrifos as there are plenty of safer pesticides available.
The authority says it is reviewing the Otago University research and will consider reassessing it if it feels any new information has come to light.