High-profile studies reporting the presence of microplastics throughout the human body have been thrown into doubt by scientists who say the discoveries are probably the result of contamination and false positives. One chemist called the concerns “a bombshell”.

Studies claiming to have revealed micro and nanoplastics in the brain, testes, placentas, arteries and elsewhere were reported by media across the world, including the Guardian. There is no doubt that plastic pollution of the natural world is ubiquitous, and present in the food and drink we consume and the air we breathe. But the health damage potentially caused by microplastics and the chemicals they contain is unclear, and an explosion of research has taken off in this area in recent years.

However, micro- and nanoplastic particles are tiny and at the limit of today’s analytical techniques, especially in human tissue. There is no suggestion of malpractice, but researchers told the Guardian of their concern that the race to publish results, in some cases by groups with limited analytical expertise, has led to rushed results and routine scientific checks sometimes being overlooked.

The Guardian has identified seven studies that have been challenged by researchers publishing criticism in the respective journals, while a recent analysis listed 18 studies that it said had not considered that some human tissue can produce measurements easily confused with the signal given by common plastics.