Bits of plastic have been detected in the faeces of people in Europe, Russia and Japan, according to research claiming to show for the first time the widespread presence of plastics in the human food chain.
All eight volunteers in a small pilot study were found to have passed several types of plastic, with an average of 20 micro-particles per 10 grams of stool, researchers reported on Tuesday at a gastroenterology congress in Vienna.
The scientists speculated that the tiny specks — ranging in size from 50 to 500 micrometres — may have been ingested via seafood, food wrapping, dust or plastic bottles.
A human hair is roughly 50 to 100 micrometres in width.
"In our laboratory, we were able to detect nine different types of plastics," said Bettina Liebmann, a researcher at the Federal Environment Agency, which analysed the samples.
The two most common were polypropylene — found in bottle caps, rope and strapping — and polyethylene, present in drinking bottles and textile fibres. Together with polystyrene and polyethylene, they accounted
for more than 95% of the particles detected.
"We were unable to establish a reliable connection between nutritional behaviour and exposure to microplastics," said Philipp Schwabl, lead author and researcher at the Medical University of Vienna.
In earlier studies on animals, the highest concentrations of microplastics were found in the stomach and intestines, but smaller amounts have also been detected in blood, lymph and the liver. "There are initial indications that microplastics can damage the gastrointestinal tract by promoting inflammatory reactions or absorbing harmful substances," Schwabl said.
"Further studies are needed to assess the potential dangers of microplastics for humans."
Schwabl recruited five women and three men, aged 33 to 65, in Finland, the Netherlands, Britain, Italy, Poland, Russia, Japan and Austria. Each kept a log of what they ate, and then provided a stool sample. They consumed foods wrapped in plastic and beverages in plastic bottles. Six ate seafood. None were vegetarians.
Scientists not involved in the study said it was too limited in scope to draw any firm conclusions. "Microplastics have been found in tap water, bottled water, fish and mussel tissue, and even in beer," said Alistair Boxall, a professor in environmental science at the University of York in Britain.