Perhaps you run an apple under water for a moment before chomping down. Perhaps you give it a good rub on your shirt, or maybe you don’t even remove the sticker before taking a bite.
But chances are, that apple was treated with pesticides to protect it from threats like insects and fungi. Pesticides can boost harvests, but some can be toxic to humans in high concentrations, according to the World Health Organization.
Fruits and vegetables do get washed before they hit the shelves — for example, with bleach solutions. But some researchers have wondered whether that wash was enough.
“We want to see whether or not the factory level (of washing) is already effective” at removing pesticides, said Lili He, a food scientist at the University of Massachusetts, Amherst. On Wednesday, He published a study comparing bleach, tap water and baking soda in removing two pesticide residues: phosmet and thiabendazole.
In the new study, baking soda came out on top. The authors say this is because the pesticides degrade faster in baking soda, making them easier to physically remove by washing.
She said this could be accomplished by mixing roughly a teaspoon of baking soda into two cups of water, though the measurement “doesn’t have to be that strict.”
Bleach, on other hand, is primarily meant to kill bacteria and other germs that might build up, He said.
In He’s study, no method was 100% effective in removing pesticides from the apples, which were not taken directly from orchards but rather coated with pesticides in the lab. This is partly because thiabendazole is a “systemic” pesticide, meaning it penetrates below the surface. He’s team estimated that 80% of thiabendazole residues were removed by the baking soda solution, versus over 95% of phosmet.
“The further the pesticides got penetrated in, the harder it was to wash away,” He said.
Her study did not test any other home cleaning methods, like vinegar, nor did she include the full panoply of pesticide residues that might be found on apples.
For this reason, “I wouldn’t be too concerned about which is the best way,” said Dr. Motoko Mukai, a toxicologist in the Department of Food Science at Cornell University’s College of Agriculture and Life Sciences who was not involved in the study.
Mukai said different pesticides may degrade — or not degrade — in the presence of baking soda or other compounds.
“It all depends on the chemical properties of the pesticide, so it’s not one fit for all,” said Mukai, who generally uses tap water alone to wash her fruits and vegetables. She added that research has shown that washing produce is effective at reducing pesticide residues, but there is “not a clear winner.”
Other types of cooking or food processing, like blanching or juicing, can also lower residue levels. You can also buy organic, Mukai said, but “it’s not entirely pesticide-free. I would still wash before consuming it.”
Another option is peeling fruit, “although that reduces the nutritional content, so that’s a tradeoff,” Mukai said.
Some experts say that pesticide levels are too low to be harmful to humans, while others warn that long-term low-level exposure could still have damaging effects — particularly on agricultural workers and their kids.
“Produce has been tested … to make sure that pesticides are below threshold of what we consider to be toxic to humans,” Mukai said.
Of the two pesticides that He tested, the USDA’s Pesticide Data Program shows only three presumed violations for thiabendazole and none for phosmet. For the USDA database, over 7,000 samples of apples were tested for each pesticide between 1994 and 2015.
Phosmet is an insecticide, and thiabendazole is an antifungal that can prevent different types of molds and rots. Thiabendazole can also be used in humans to treat parasites such as roundworms, but in much greater doses than might be found on a storebought apple, according to the EPA.
Environmental officials have “determined the extremely low levels of those residues are not a food safety risk, and the presence of such residues does not pose a safety concern,” according to the USDA.
“We have pretty good control of pesticide amount,” He said. “That doesn’t ensure that there’s no risk at all.”
“What we really can do is reduce the risk” by washing, she added.
Experts say the health benefits of eating fruits and vegetables far outweigh any potential pesticide risk.
The FDA recommends washing all produce under running water, even if you don’t plan to eat the skin. Firm fruits and veggies, like apples and cucumbers, should be scrubbed with a produce brush before drying with a clean towel, the agency says.
When it comes to buying organic, the jury is still out as to whether there are solid health benefits. According to one study, “our findings do not indicate that substituting organic … commodities for conventional forms will lead to any measurable consumer health benefit.”
As for He, she prefers to play it safe for her two children, ages 3 and 7.
“For my kids, I’m going to wash longer. Maybe I’ll add a little bit of baking soda in there,” He said. “If it’s just me, I’ll probably just wash it a few seconds.”
She did not eat the apples after her experiment.