Washing Produce Such as Apples and Cucumbers May Not Be Enough to Remove Pesticides, Study Finds

Many consumers are familiar with the routine of buying fruits and vegetables, bringing them home and washing them in the sink to remove pesticides and other contaminants from the outer layer before preparing and eating it. But according to new research, washing produce is likely not effective enough at removing the residue from pesticides.

The study, published in the journal Nano Letters, explained how researchers developed a form of surface-enhanced Raman spectroscopy (SERS), resulting in a high-tech method of imaging that they then used to examine levels of pesticide residues on produce. Although the research paper focused on the technology created by the authors, it also raised concerns over pesticides and food safety based on what the technology found in experiments.

The researchers created a flexible and nearly transparent membrane made from a cellulose hydrogel film that was stretched and wrinkled, then coated in silver nitrate solution, as explained by the American Chemical Society. This created a membrane that could use SERS, which can detect trace amounts of certain compounds, specifically for inspecting for pesticides.

After developing this pesticide-detecting membrane, the researchers put their development to the test. To do so, they started by spraying two pesticides, thiram and carbendazim, on apples, then left the apples to dry.

Once the apples had dried, researchers followed the same procedure consumers would after purchasing produce at the store: washing the apples. After washing, they used the membrane over the whole, unpeeled apples and applied the SERS method. This revealed trace amounts of the pesticides that had been applied both on the apple’s skin and even on the outer layer of apple pulp.

“This indicates that the pesticides penetrated the pulp layer and that traditional fruit-cleaning operations cannot wholly remove pesticides,” the authors wrote in the study.

However, when the researchers peeled the apple, it removed enough of the fruit that had detectable pesticide levels. As such, the authors wrote, “… we believe that the peeling operation can effectively avoid the hazards of pesticides in the fruit’s epidermis and near-epidermal pulp, thereby reducing the probability of ingesting pesticides.”

The team’s new imaging method using SERS could also be used on other food products. In their research, the study authors found that their development could be useful in analyzing contaminants on foods such as chili powder, rice, cucumbers and even shrimp.

“This is actually useful for understanding how these pesticides move in,” Michael Hansen, a senior scientist at Consumer Reports, told The Guardian. “This is more science showing that, yes, there are concerns. Don’t just think that washing is going to help you.”