Plastic nanoparticles can be released from plastic containers into food when they are heated in a microwave oven, a new study shows.
A team from the University of Nebraska-Lincoln in the US conducted experiments using children’s food containers made of polypropylene and polyethylene, which are both approved by US Food and Drug Agency (FDA) regulators for safe use.
After heating for three minutes in a 1,000-watt microwave oven, various liquids placed in the containers were analyzed for the presence of microplastics (at least 1/1000th of a millimeter in size) and nanoplastics (even smaller).
The number of particles varied, but the researchers estimated that three minutes of microwave heating could release 4.22 million microplastic particles and 2.11 billion nanoplastic particles from one square centimeter of plastic.
“When we consume certain foods, we are usually informed or have an idea of their calorie, sugar and other nutrient content,” said civil and environmental engineer Qazi Albab Hussain of the University of Nebraska-Lincoln.
“I think it’s also important to know the amount of plastic particles present in our food.”
The researchers found that heating water or dairy products in polypropylene or polyethylene containers in a microwave oven was likely to result in the highest relative concentration of plastic. Particles were also released when food and beverages were stored in the refrigerator and at room temperature, but in much smaller amounts.
It is still unclear what effect these microscopic plastic particles have on us. Studies have shown that they could potentially be harmful to the gut and key biological processes, but scientists are not yet certain.
However, it’s probably safe to say that the less plastic we consume, the better. Embryonic kidney cells cultured by the researchers, which were exposed to plastic particles in concentrations released by containers over several days, showed potential hazards.
The team found that 77 percent of kidney cells exposed to the highest concentrations of plastic were destroyed. While this does not mean that our kidneys will necessarily be directly exposed to such concentrations, it does provide insight into the potential toxicity of these microplastics and nanoplastics, especially in developing organisms.
While more detailed research and testing will be needed to determine how harmful these plastic particles are when they enter the body, it is clear that this is an issue that needs to be studied. Our addiction to plastic can cause significant harm to what we consume.
“We need to find polymers that release fewer particles,” says Hussein.
“I hope that the day will come when these products will be labeled ‘microplastic-free’ or ‘nanoplastic-free’.”
The study was published in the journal Environmental Science & Technology.