By Steven Mew, the Australian Science Media Centre

This week US scientists released research which found that 22 pesticides are statistically linked with an increased risk of prostate cancer in the USA, including the widely used herbicide glyphosate. Of these 22 pesticides, four were also linked with an increased risk of death from prostate cancer, including the herbicide trifluralin and the insecticide thiamethoxam, which are both approved for use in Australia.

To get these results, the researchers analysed the use of 295 pesticides from farm surveys in over 3,000 US counties. They then compared the data with prostate cancer rates in the same counties 10-18 years later, to account for the slow-growing nature of prostate cancer. Using statistical analysis, the team found associations between the use of 22 pesticides and the risk of prostate cancer.

Bur Professor Oliver Jones from RMIT University told the AusSMC that he finds the evidence in the paper quite weak.

“The authors don’t actually say that pesticides cause prostate cancer, just that they found 22 pesticides that were statistically associated with prostate cancer and that more research is needed,” he said.

“An association between two things does not mean one caused the other; it is just an observation. The work is based on statistics, not direct experiments and the data on pesticide usage and exposure were estimated, not actually measured,” Prof Jones said.

According to Prof Jones, if instead of looking at pesticide usage, we changed the study to look at age, sleep, or lack of exercise, and ran the same tests using the same health records in the study we would likely find more associations, but it would not mean these things caused cancer, just that there was an association.

Professor Adrian Esterman from the University of South Australia agreed that the study has limitations.

"It uses county-level data, which may not directly apply to individual exposures, and can only demonstrate associations rather than causation," he said, adding that despite these limitations, the study could have implications for public health and agriculture. He also said the study underscores the need for further research into the potential long-term health effects of pesticide exposure.

While we wait for more research to be conducted, Prof Jones says the current evidence for harm is not strong if herbicides are used as directed.

“The other thing to remember is the adage that the dose makes the poison, everything is a poison if you have enough of it, including water,” he said, pointing out that plenty of people use herbicides and don’t get prostate cancer.

“The biggest risk factors for prostate cancer are age and genetics, neither of which we can control,” he said.

You can read the full AusSMC Expert Reaction here.

This article originally appeared in Science Deadline, a weekly newsletter from the AusSMC. You are free to republish this story, in full, with appropriate credit.

Contact: Steven Mew

Phone: +61 8 7120 8666

Email: info@smc.org.au