Weed killer worry

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A Massey University public health expert says Queenstown’s council should stop its contractors using the potentially cancer-causing chemical herbicide Roundup.

The chemical (Glyphosate 360) is used in Queenstown, the council has confirmed.

Senior research fellow at the Centre for Public Health Research, Dr David McLean, says the most sophisticated and exhaustive review of its carcinogenicity concluded glyphosate was a probable human carcinogen.

That was conducted by the International Agency for Research on Cancer (IARC) in 2015.

The IARC does not make these judgements lightly, he says.

“Unfortunately there is a huge vested interest in the continued sale of this product, and this has influenced what regulators have done about the IARC finding,” McLean says.

He says the New Zealand Environmental Protection Agency had also denied the IARC finding and “had done nothing to inform the public of the potential risk from using glyphosate”.

In McLean’s opinion, “it would be prudent of the council to avoid using a product that is likely to cause cancer – to protect both its workers (or contractors) and the public”.

Council spokesman Jack Barlow says alternatives have “so far proved ineffective and expensive”.

“In the future, should any of these turn out to be cost-efficient and effective they would be considered for use,” he says.

Christchurch City Council voted to stop using glyphosate in March 2016.

It switched to organic plant derived herbicides for controlling weeds in its community, sports, regional parks and amenity gardens.

Hand weeding in council parks occurred before the decision and has continued since.

However, other councils such as Auckland, Dunedin, Wellington, Hamilton, Invercargill, Porirua, Hutt and Tauranga councils all use glyphosate in their weed control programmes.

University of Otago toxicologist Dr Belinda Cridge says glyphosate isn’t perfect but there are no effective alternatives.

“We don’t want to go back to those days of spraying weedkillers like 2,4,5-T or 24D and arsenic, some of our farming land is really heavily contaminated because of the chemicals we used back then.”

She says using anything to excess is what causes problems “even the organic herbicide cider vinegar can cause harm if you use too much of it”.

Barlow says the chemicals used in Queenstown council’s weed management include Organosilicone, Blue Marker Dye, Meturon, Trichloram Brushkiller and Glyphosate 360.

Contractor Downer (via Delta) carries out vegetation maintenance throughout the area twice a year in Queenstown, he says.

If a property owner or resident does not want the council contractors to spray their road frontage, they could apply to be on the ‘no spray’ list.

ed@scene.co.nz