Scientists define microplastics as plastic fragments less than 5 mm, about 0.2 inches (D). Much previous research on microplastics and nanoplastics have focused on its accumulation and effects in marine life, with particular focus on seafood that human's consume. Microplastics have been associated with neurotoxic effects in wild fish and increase oxidative damage which can theoretically lead to a greater risk of cancer.

Humans do ingest microplastics and they do at least pass through the digestive system as evidenced by the finding that they were widely found in fecal samples from people all over the world. Very little is known about whether they go elsewhere in the body after ingestion or what health effects they have.

Human tissue samples from a large repository which was set up to study neurodegenerative conditions such as Alzheimer’s disease and developed a new method to test the samples for plastics. They artificially spiked the samples with microplastics to test their new method and were able to detect the plastics.