This claim originated from a 2019 report by the World Wildlife Fund (WWF), which was based on a study by researchers at the University of Newcastle in Australia. The study estimated that humans might ingest up to 5 grams of microplastics per week, which is roughly the weight of a credit card. However, this is an estimate, and the actual amount can vary based on different factors like diet, location, and lifestyle.

And note the word MIGHT.