A new study has found the worms excrete plastic and its toxic additives with no residue in their bodies.
The humble mealworm might be able to help with our plastic problem. These tiny insects are commonly raised for animal feed and are slowly entering the human diet as a more ethical, low-carbon form of protein. They are known to eat almost anything, including plastic, but researchers from Stanford University wanted to see what would happen when mealworms were given polystyrene foam containing toxic fire retardant chemicals. Building on earlier research, they were curious about whether the chemicals would remain in their bodies or get excreted.
Polystyrene foam is notoriously difficult and expensive to recycle, due to its low density and bulkiness. It also uses large quantities of fire retardants; an estimated 25 million metric tons of hexabromocyclododecane (HBCD) were added to polystyrene foam in 2015 alone. These chemicals are persistent in the environment and "can have significant health and environmental impacts, ranging from endocrine disruption to neurotoxicity. Because of this, the European Union plans to ban HBCD, and U.S. Environmental Protection Agency is evaluating its risk."Enter the industrious mealworm, which was able to excrete the polystyrene it ate as partially degraded fragments and carbon dioxide. The fire retardant chemicals came out, too: "With it, they excreted the HBCD – about 90 percent within 24 hours of consumption and essentially all of it after 48 hours." The researchers said the mealworms ingesting HBCD-laced polystyrene were just as healthy as the ones eating a normal diet, as were the farmed shrimp that were fed those plastic- or non-plastic-eating mealworms.
Lead study author Anja Malawi Brandon said, "This is definitely not what we expected to see. It's amazing that mealworms can eat a chemical additive without it building up in their body over time."
This does not mean we should become complacent and keep adding fire retardants to polystyrene foam, or even continue using polystyrene foam. Both need to be phased out and replaced with easier-to-recycle or -biodegrade alternatives, preferably reusables. Brandon says it's a wake-up call, despite the mealworms' surprising ability. "It reminds us that we need to think about what we're adding to our plastics and how we deal with it."
Study published in Environmental Science and Technology
This article has been updated to remove an incorrect reference to Styrofoam (TM) extruded polystyrene foam, which was not tested in the study.