Could tiny mealworms help tackle plastic pollution? Research by Stanford University shows they can eat styrofoam - containing a common toxic chemical additive - and still be safely eaten by other animals in the food chain.
A previous study had already shown that mealworms are able to consume various forms of plastic.
The latest Stanford study, published in Environmental Science & Technology, is the first to look at where chemicals in plastic end up after being broken down in a natural system – in this case a yellow mealworm’s gut.
“This is definitely not what we expected to see,” said study lead author Anja Malawi Brandon, a PhD candidate in civil and environmental engineering at Stanford.
“It’s amazing that mealworms can eat a chemical additive without it building up in their body over time.”
In earlier work Stanford researchers and collaborators at other institutions revealed that mealworms, which are easy to cultivate and widely used as a food for animals ranging from chickens and snakes to fish and shrimp, can subsist on a diet of various types of plastic.
They found that micro organisms in the worms’ guts biodegrade the plastic in the process.
Before the latest study there was concern about whether the mealworms were safe for other animals to eact.
“This work provides an answer to many people who asked us whether it is safe to feed animals with mealworms that ate styrofoam”, said Wei-Min Wu, a senior research engineer in Stanford’s Department of Civil and Environmental Engineering - who has led or co-authored most of the Stanford studies of plastic-eating mealworms.
While 'hopeful for mealworm-derived solutions to the world’s plastic waste crisis' the researchers caution that 'lasting answers will only come in the form of biodegradable plastic replacement materials and reduced reliance on single-use products'.
“This is a wake-up call,” said Brandon. “It reminds us that we need to think about what we’re adding to our plastics and how we deal with it.”
Brandon, Wu and their colleagues looked at styrofoam or polystyrene, a common plastic typically used for packaging and insulation, that is costly to recycle because of its low density and bulkiness.
It contained a flame retardant called hexabromocyclododecane, or HBCD, that is commonly added to polystyrene.
The additive is one of many used to improve plastics’ manufacturing properties or decrease flammability. In 2015 alone, nearly 25 million metric tons of these chemicals were added to plastics, according to various studies. Some, such as HBCD, 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.
Mealworms in the experiment excreted about half of the polystyrene they consumed as tiny, partially degraded fragments and the other half as carbon dioxide.
With it, they excreted the HBCD – about 90 percent within 24 hours of consumption and essentially all of it after 48 hours.
Mealworms fed a steady diet of HBCD-laden polystyrene were as healthy as those eating a normal diet.
The same was true of shrimp fed a steady diet of the HBCD-ingesting mealworms and their counterparts on a normal diet.
The plastic in the mealworms’ guts likely played an important role in concentrating and removing the HBCD.
The researchers acknowledge that mealworm-excreted HBCD still poses a hazard, and that other common plastic additives may have different fates within plastic-degrading mealworms.
The research was funded by the Stanford Woods Institute for Environment, the National Science Foundation and the Stanford Interdisciplinary Graduate Fellowship.