What is the risk of pesticides in Australian food?
Dr Ian Musgrave, a toxicologist at the University of Adelaide, said that despite the high use of pesticides in Australian agriculture, the risk from residues in Australian produce was “extraordinarily low”.
“People tend to overestimate the concentrations of pesticides on fruit and vegetables,” he said.
There are mandatory withholding periods – time between when a pesticide is applied to a crop and when it is allowed to be harvested – which in theory allow for chemicals to break down and residue levels to decrease.
Many of the pesticides that are used on food crops today, such as certain organophosphate insecticides (carbamate, dimethoate), break down rapidly in sunlight or water and do not accumulate in the food chain.
The widely used herbicide glyphosate, for example, only lasts a couple of days in surface waters, said Dr Sarit Kaserzon, a senior research fellow at the Queensland Alliance for Environmental Health Sciences at the University of Queensland, who has conducted degradation tests of the chemical. In soils, it degrades in several days to several weeks. (Kaserzon’s research has found glyphosate exposure in an estimated 8% of the general Australian population.)
These are in contrast to older pesticides, such as polychlorinated biphenyls, which degrade very slowly and accumulate in the human body. Most of these have been banned since the Stockholm convention on persistent organic pollutants was signed in 2001.
The most recent available information for pesticide levels in Australian food was compiled by Food Standards Australia New Zealand. Their 25th Total Diet survey, published in 2019, found that 2%, or 11 of 508 samples, had chemicals present in greater amounts than the maximum residue limits – the maximum concentrations that are set by the regulator as allowable in foods. These included chlorpyrifos in green beans and cucumbers, and dithiocarbamates in broccoli.
As the Guardian has reported, the samples were collected during one week in May 2013 and one week in February 2014.
Estimated dietary exposures for the organophosphate insecticide prothiofos exceeded the acceptable daily intake for some population age groups, FSANZ noted, which led to regulatory changes in the way the chemical is used.
Does washing fruit and vegetables remove the pesticide or should they be peeled?
Kaserzon suggests “washing everything you bring home. We know that dilution is a good way of getting rid of any residues on your products”.
Musgrave agrees: “The majority all wash off quite nicely.”
Washing food has other benefits. “Probably the biggest reason for washing fruit and vegetables is not to get rid of pesticides, but to get rid of any contaminating bacteria that might be on the fruit and vegetables,” said Musgrave. Research has also shown that washing rice before cooking, for example, reduced plastic contamination by 20 to 40%.
FSANZ recommends “scrubbing and washing whole fruits and vegetables in running water or removing the skin, where possible, prior to consumption or cooking”.
But, Musgrave points out, this may result in the loss of the nutritional value found in the skin of fruits and vegetables. “Apple peel and potato peel actually contain nutrients which are quite useful,” he said.
Kaserzon said peeling and washing fruit and vegetables would only be effective at removing pesticides that have been sprayed with chemicals on their surface. “If something was sprayed in germination, [the pesticide] would make its way into the root system and it would be in the whole fruit,” she said. She added that workers who handle fruit and vegetables are at higher risk of exposure to pesticides than consumers.
Should I buy organic?
Some people may choose to opt for organic produce – food made without the use of synthetic chemicals or genetically modified components. Unfortunately it’s usually more expensive.
Depending on the product, pesticide residues can be lower in organic food. But some naturally occurring pesticides are permitted for use in organic farming and include pyrethrins, light oils, copper, sulphur and biological substances. Organic produce should also be washed prior to consumption.
I’m worried about the environmental impact of my diet – is there anything I can do?
“No food is grown without an environmental impact,” said Dr Brad Ridoutt at the CSIRO. He co-authored a study looking into the environmental pesticide impacts of Australian dietary choices.
“Energy-dense and nutrient-poor discretionary foods, fruits, and protein-rich foods were the sources of most of the dietary pesticide impacts,” the research found.
“Different foods have different types of impacts – some use a lot of water, others use a lot of pesticides, others emit more greenhouse gases etc,” Ridoutt said. “Often people are advised to avoid these foods or those foods for the sake of the environment, but then they often end up reducing one environmental burden and increasing another.
“There’s some things that consumers can achieve for the environment, but if we really want to improve the sustainability of our food system, the heavy lifting has to be done in the agricultural sector – the food producers.”
“There’s a limit to what you can achieve for the environment by changing your diet. A major burden of the Australian diet in terms of pesticide toxicity in the Australian environment comes from fruit and vegetables. Vegetables are the most under-consumed food group according to dietary recommendations … you don’t want to be going down the pathway of saying that to reduce environmental impacts you want to avoid vegetables,” said Ridoutt.
• This story was amended on 29 September 2022 to clarify when Food Standards Australia New Zealand’s pesticide data was collected, and to make a distinction between the degradation of glyphosate in surface water versus its degradation in soil.
