‘Cocktail of pesticides’ – including chemical banned for decades – detected in wild oysters

Tests have revealed the presence of a “cocktail of pesticides” – including traces of a chemical that was banned almost 20 years ago – in a major New South Wales waterway and the wild oysters that inhabit it.

The data was collected in 2020-21 and the results of the Richmond River study were published in the Journal of Environmental Pollution this week.

Southern Cross University marine science professor Kirsten Benkendorff said 21 different pesticides were detected in the river near Ballina.

The researchers found more pesticides in the wild oysters than in the water.

There was an average of nine different pesticides detected in individual oyster samples.

Dr Benkendorff said the concentration of several pesticides exceeded safe environmental guidelines.

“There was a whole cocktail of pesticides in oysters and the water,” she said.

“It’s a serious concern of the health of the environment and potential consumer safety.”

The fungicide benomyl, which has been illegal to use since 2006, was also detected.

“It is a really big concern to have found a banned pesticide in our water here — we don’t know who is using it or why,” she said.

“It’s a pesticide with a pretty short half-life, so it’s not something that has been hanging around in the environment for a long time.”

Some of the pesticides identified in the report are used for roadside weed spraying and for maintenance of playing fields.

Most of the chemicals detected in the study are registered for use in the production of sugarcane.

“It demonstrates there is a range of different sources of pesticides, even when we consider agriculture as the main focus,” Dr Benkendorff said.

Cane industry blindsided

The testing revealed high levels of the herbicides atrazine and diuron were detected in March 2020 at a testing site near a cane drain at Empire Vale, south of Ballina.

NSW Canegrowers chairman Ross Farlow said it was difficult to work out the exact source so long after the event.

“It’s almost four years now since that data was collected and you would have to wonder why the data has been sat on and held and not flagged at the time,” he said.

“If there was an issue of alarm, why wasn’t it raised with the agricultural industries across the floodplain and something could have been investigated immediately?”

Australian Macadamia Society chief executive officer Clare Hamilton-Bate said two of the 21 chemicals were registered for macadamias.

One is the fungicide tebuconazole, the other is iprodione; which she says isn’t used due to residue limits in key export markets.

“We have flagged our disappointment that there was no consultation and, it would appear, little agronomic knowledge of what is used in the macadamia industry,” she said.

Water quality in the Richmond River has been a matter of concern for many years.

A 2015 University of New England study gave the river a D-plus health rating.

Aquatic veterinarian Matt Landos said he was not surprised by the results.

“We haven’t reformed our regulation of pesticides to make them safe,” he said.

“The detection of benomyl shows the product is still in use and someone is using that product illegally.”

Oysters ‘should be safe’

The Australian Pesticides and Veterinary Medicines Authority (APVMA) is responsible for reviewing and approving pesticides up to the point of sale.

The NSW Environment Protection Authority (EPA) regulates the use of pesticides.

An EPA spokesperson was not available for an interview, but said in a statement that the agency welcomed the work done by Southern Cross University and took the misuse of pesticides and their potential impacts seriously.

The EPA has commenced a compliance campaign targeting horticultural farms near Emigrant Creek.

The report authors are calling for further pesticide contamination research higher in the Richmond catchment, as well as in other estuaries.

Co-author Amanda Reichelt-Brushett said she did not want to put people off eating their oysters.

“They should be safe if you have bought them from a good farm,” she said.

Richmond River oyster grower Geoff Lawler said he was concerned but not surprised that pesticides were found in the estuaries.

He said his commercial oysters were tested in 2020, the same year as when this research was carried out, and found to be pesticide-free.

“We’re controlled by the NSW Food Authority, they apply the Food Standards Act,” he said.

“If there was any problem they would have simply prevented us from harvesting.”