The decision by the International Agency for Research on Cancer (IARC) to label glyphosate a probable human carcinogen has not been followed by risk assessment bodies ceasing or restricting its use, Cridge, of the university’s pharmacology and toxicology department, said.
Herbicides containing glyphosate are used in about 90 countries, most commonly as Roundup.
A more immediate risk to its future use is the $440 million in damages awarded by a California Superior Court jury against Monsanto to a school groundskeeper who claimed using Roundup contributed to his terminal cancer.
The case is under appeal and if unsuccessful other claims could follow, she said.
Regardless of the outcome social pressure rather than toxicity could influence Monsanto’s decision on Roundup’s future, which would be an issue for agriculture.
She has not seen any scientific evidence that products with glyphosate are dangerous when handled correctly.
“Based on what we know at the moment I can’t see any reason for the current state of play to change.”
She said IARC made its decision after reviewing published papers to assess if products can cause cancer, a process that had previously concluded red meat and alcohol are probable human carcinogens.
The glyphosate decision was based on an epidemiological study that found slightly higher cancer rates but others refuted that finding.
The assessment process took no account of risk factors or mitigation steps that could make such products safe to use.
“They don’t talk about how much glyphosate someone needs to come into contact with, they don’t consider protective gear, whether it is breathed in or comes into contact with the skin.
“All they talk about is that some people did some studies and determined there is a probable risk.”
Cridge is not aware of any environmental protection agencies (EPA) or their equivalents around the world ramping up controls or ending its use.
NZ’s EPA has not included glyphosate on a list of 40 chemicals it plans to reassess.
EPA chief executive Dr Allan Freeth has announced changes to the management of chemicals including reassessing 40 to ensure risks to people and the environment are being managed effectively.
The list includes many agricultural herbicides and pesticides such as paraquat, trifluralin and brodifacoum.
Freeth said the changes will give people confidence the EPA is properly managing their health and environmental concerns.
Cridge has studied the toxicology of chemicals used on farms and in a paper, Toxicology and the NZ Farmer, she said glyphosate inhibits the enzyme EPSPS, essential for protein production in plants.
“This means that it is highly specific for plants and exhibits relatively low toxicity in humans and animals.”
It has low toxicity in adults because it is poorly absorbed, is not easily metabolised by the body and does not accumulate in tissue.
Meanwhile, a Canterbury University study found bacteria develop antibiotic resistance up to 100,000 times faster when exposed to herbicides such as Roundup and Kamba and antibiotics compared to no exposure to herbicide.
One of the study’s authors Professor Jack Heinemann said it adds to growing evidence herbicides used on a mass industrial scale but not intended to be used as antibiotics can have profound effects on bacteria.
That can potentially lead to negative implications for medicine’s ability to treat infectious diseases caused by bacteria.
“The combination of chemicals to which bacteria are exposed in the modern environment should be addressed alongside antibiotic use if we are to preserve antibiotics in the long-term,” he said.
