Banning the common weed-killing ingredient glyphosate is premature and would change farm practices worldwide, a weed scientist says.
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A World Health Organisation (WHO) committee announced last year glyphosate was probably a carcinogenic.
Last week, the Green Party said the Environmental Protection Agency (EPA) should urgently review the safety of the ingredient and called for its use in public spaces to be banned.
A former director of the American National Center for Environmental Health, Dr Chris Portier, told Nine to Noon governments and international bodies need to accelerate research on glyphosate.
The environmental scientist said although scientists knew the chemical posed a hazard, they still needed to figure out how dangerous it really was.
"Looking at the trace amounts of glyphosate in people's blood and trace amounts in their urine, I would put it as a very high priority and a high concern because so many people were exposed I think it needs to be looked at very very carefully and with a very rigorous scientific review," said Dr Portier.
Listen to Dr Portier on Nine to Noon
But Massey University weed scientist Dr Kerry Harrington said it was the main herbicide used in New Zealand because of its effectiveness; it killed crops quickly and then deactivated.
"It's deactivated almost immediately when it hits soil colloids and that's why it's used for preparing land for planting crops. You can plant the next day or even the same day," Dr Harrington said.
The current hazard rating was roughly equivalent to burning wood in a fireplace or being a shiftworker, he said.
In the European Union, a bitter row has erupted since last year's WHO hazard report.
The EU bans all carcinogenic pesticides, but its food regulator dismissed the WHO report saying the science is not strong enough.
The Environmental Protection Authority said it was actively monitoring the status of glyphosate, but believed it was still safe to use as a herbicide.