Researchers at Vrije Universiteit Amsterdam developed a method to detect and measure plastic particles as small as 700 nanometres in whole blood, then applied it to samples from 22 healthy adult volunteers.
Plastic was quantified in 17 of the 22 people (77%), with an average concentration of 1.6 micrograms per millilitre. PET (used in drink bottles), polyethylene (bags and packaging) and polystyrene were the most common polymers.
This was the first proof that plastic particles circulate in the human bloodstream and can therefore reach organs. It opened the door to the wave of studies that followed on placenta, brain, heart and other tissues.
It was a small pilot study, described by its own authors as pioneering. It says nothing about health effects, and the concentration figure should not be extrapolated to the population.