A widely circulated claim suggests individuals consume the equivalent of a credit card’s worth of microplastics weekly. However, this assertion, while alarming, is not supported by the reality of a typical human diet. This claim gained traction alongside numerous studies identifying microplastics in diverse environments, from remote mountaintops to the ocean’s depths, and within human tissues like the heart, liver, kidneys, breast milk, and bloodstream. The ubiquitous presence of microplastics, coupled with scientific findings suggesting potential harm, understandably sparks significant concern.
The pervasiveness of microplastics is a testament to the remarkable properties of plastic itself. The invention of Bakelite in the early 20th century marked a paradigm shift, enabling the mass production of materials not reliant on natural resources. As plastics evolved to become thinner and more economical, their application expanded dramatically, transforming food packaging, electronics, and medical devices. Yet, this very durability presents a challenge. Tiny plastic particles have been released into the environment for over a century, persisting due to their long lifespan. This persistence explains their detection in the tissues and blood of various organisms throughout the food chain, including humans, as well as in common consumables like salt, beer, and drinking water.
The Unsubstantiated Credit Card Claim
Many sensational headlines in recent years have overstated the microplastic consumption issue, often by being imprecise about particle size or by referencing studies employing unrealistically high doses. The viral assertion that the average person ingests five grams of microplastics weekly, equivalent to a credit card, originated from a 2019 study. This work, unfortunately, employed flawed calculations and is inaccurate under normal dietary circumstances.
This particular study, funded by the World Wildlife Fund in collaboration with the University of Newcastle, was a literature review consolidating findings from 59 prior investigations into microplastics in food and water. A fundamental issue arose from the disparate methodologies of the included studies: some quantified microplastic particles by count, while others measured their mass. This discrepancy necessitated estimations by the researchers for comparative analysis. For instance, the study estimated microplastic mass in drinking water by extrapolating from ocean water measurements and drinking water particle counts per liter. However, microplastics found in the ocean and in our tap water are not necessarily identical. If the average particle size in oceanic samples is significantly larger than in filtered drinking water, the resulting mass calculation can be inflated. Subsequent analyses of the same data confirmed this potential for exaggeration.
Consequently, the notion that we consume five grams of microplastics weekly is incorrect; the actual intake is likely considerably lower. One study indicated that a significant portion of the global population ingests a mere 0.0041 milligrams of microplastics per week, a quantity less than a grain of salt. At this rate, consuming the equivalent of a credit card’s worth of plastic would take over 1.2 million weeks, or more than 23,000 years.
The same research team conducted simulations predicting a lifetime accumulation of approximately 12.2 milligrams of microplastics per person. Crucially, their models suggested that only about 41 nanograms would actually be absorbed by the body.
Concerns Regarding Detection Methods
More recent concerns have surfaced regarding the scientific rigor of studies examining microplastic levels within the human body. Some methodologies involve vaporizing tissue samples and analyzing the resulting fumes for microplastic presence. However, the vaporization of fatty tissue can yield molecules that mimic those produced by microplastics, potentially leading to false positive results.
Understanding the Effects of Microplastics in the Body
While addressing the quantity of ingested microplastics is one aspect, understanding their biological effects presents another, less clear-cut question. Some research indicates behavioral changes and inflammation in mice exposed to microplastics. However, the doses administered to these animals were exceptionally high, making direct extrapolation to human exposure levels difficult. A study involving pigs exposed to one gram of microplastics per week observed alterations in gene expression and induced oxidative stress in the pancreas. Yet, these dosages also remain unrealistic for typical human exposure.
In 2022, the World Health Organization issued a report highlighting that many animal studies utilize microplastic concentrations far exceeding typical human exposure levels or employ particle sizes unlikely to be absorbed by the human body. The report further noted that microplastic circulation within mammalian organs differs from that in rodents, complicating the translation of findings to humans.
Preliminary human studies do exist. One recent investigation identified microplastic accumulation within arterial plaques, alongside fats, cholesterol, and blood cells. While individuals with these plastic-infused plaques exhibited a higher incidence of heart attack and stroke, it is crucial to note that these findings indicate correlation, not causation.
The complexity of microplastic effects on human health is substantial. While microplastics may contain chemicals capable of disrupting bodily functions, risk assessment requires considering the actual rate of chemical leaching into the body. Research suggests that typical leaching rates in the gut result in negligible increases in localized tissue chemical concentrations. Furthermore, these accumulated chemicals can eventually leach out of tissues and be expelled from the body.
Concerns persist regarding the potential for microplastics to transport other attached toxins into the body, interfere with immune responses, or induce cell damage and inflammation. However, it remains unknown whether microplastics pose a greater risk in these regards compared to other environmental factors like air pollution, sun exposure, excessive sugar consumption, or common infections.
While the possibility of microplastic harm to human health is understandable and warrants further investigation, particularly given growing societal anxieties about pollution, it is essential to base conclusions on robust scientific data. The field of microplastic research is still nascent, and comprehensive, rigorous data on their effects within the human body is largely absent. Therefore, focusing attention on more established health concerns may be advisable until more definitive research emerges.