No, you don't eat a credit card worth of plastic every week. But you still swallow a lot of it

Imagine enjoying a fresh salad, a juicy steak or a fluffy pastry. As your taste buds savor the various flavors, the enjoyable experience is suddenly and unpleasantly interrupted by a loud crunch sound. When you spit out your food and look at the contents, you discover to your horror that there is a credit card embedded within your meal.

The good news is that, if this experience has ever literally happened to a person, it is definitely not common. The bad news is that — while humans are not literally eating credit cards — the problem of plastic pollution is so pervasive that, in one sense, we might as well be eating them. That is why in 2019 the World Wildlife Fund famously declared — using research from the University of Newcastle, Australia — that people eat the equivalent of a credit card's worth of plastic every week. While it may not sound like a big deal to learn that you are ingesting 5 grams of plastic every week, the statistic hits more viscerally when compared to a literal credit card.

Yet to what extent are humans actually consuming all of this plastic? And more importantly, what kind of risks are involved with eating these materials? To get to the bottom of these questions, Salon spoke by email with Dr. Douglas Walker, an Associate Professor of Environmental Health at Emory University Rollins School of Public Health.

"This comparison arose from findings suggesting humans ingest approximately 0.1 [to] 5g of plastic particles per week from a variety of exposure sources," Walker explained. "The original findings were for all plastics. We do not actually eat a credit card each week and this phrase was meant as a comparison to provide context on how much plastic this could equate to."

In terms of how humans consume this plastic — most folks wouldn't ingest this stuff on purpose — Walker noted that it enters our bodies from every available source: food, water, even the air we breathe. That doesn't equate to exactly five grams of polyvinyl chloride (the plastic credit cards are made of), but could be a whole assortment of different types and compositions of plastic and its byproducts. Some people may ingest less than five grams, others may find themselves consuming more.

Yet beyond that, the problem of plastic consumption and its health consequences remains frustratingly enigmatic.

"While these findings (and others) are an important first step in understanding microplastic exposure burden, it is important to recognize these are predictions and do contain uncertainty, especially since so little is still known about the extent of microplastic exposure," Walker told Salon. "Further, these findings are only providing insight on consumption, and does not tell us about whether these particles are absorbed or have any health effects. We will need further development and application of methods that measure individual plastic exposure levels to evaluate these findings, which is one of the areas my laboratory is focused on."

Dr. Shanna Swan, a professor of environmental medicine and public health at Mount Sinai School of Medicine in New York City, has at least a few clues about the ultimate health consequences of all this plastic consumption. In her 2017 book "Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race," Swan documented plummeting human sperm counts and established a potential link to plastic pollution. At the same time, Swan pointed out that it is extremely difficult to definitively prove that this global problem is caused by endocrine disruptors in plastics like phthalates and bisphenols. This task is not impossible, but it has taken a lot of time.

Want more health and science stories in your inbox? Subscribe to Salon's weekly newsletter The Vulgar Scientist.

"This research is underway, but measurement of actual plastic particles (micro and nano plastics) in human tissue is very new (and expensive)," Swan told Salon by email. "How these concentrations relate to exposure via these sources is not yet known." Nevertheless, Swan insisted that "there are 20 years of science (including mine), in animals and humans, documenting adverse health effects of metabolites of chemicals in plastic. The number of these chemicals is staggering. I've seen over 2,000 cited. We have only begun to identify the adverse health effects."

Walker elaborated on this, writing to Salon that although there is copious data on specific plastic-related chemicals like phthalates and BPA, "we are still in the early stages of evaluating whether these particles may be toxic and have toxic effects."

As an example of one of the challenges faced by researchers, Walker pointed to a recent study published in the journal Environmental Health Perspectives which found — when trying to experiment on the effects of microplastics in placenta cells — that the "pristine particles we used differed chemically from environmentally weathered particles, which raises concerns about what are the most realistic particles to use in our laboratory experiments for studying plastic toxicity."

He later added, "Current estimates suggest that over 10,000 unique chemicals are linked to chemical manufacturing, many with unknown health effects and others identified as chemicals of concern. With such a large number of chemicals, it is very challenging to identify the key exposures we should be measuring to study health impacts of microplastics, as well as understanding their levels in humans."

Then again, even if scientists have yet to document all of the adverse health effects associated with plastic consumption, there are some things they can figure out through common sense.

"I think it is important to note that micro and nanoplastics (MNPs) can increase the body burden of the previously recognized — and often studied — chemicals in plastic (most notably phthalates, bisphenols, parabens etc.)," Swan pointed out. Just like any air pollution particles, "these harms from the chemicals brought into the body these small particles can pose a threat because of their physical presence."