Do humans ingest 50 plastic bags worth of microplastics a year?

Microplastics, tiny plastic particles less than 5 millimeters in size, have become a ubiquitous environmental pollutant. Recent claims have suggested that humans might ingest the equivalent of 50 plastic bags worth of microplastics annually. This article evaluates the validity of such claims by examining current scientific evidence, considering the methodologies of relevant studies, and comparing the data to common everyday objects. 

Microplastics enter the human body through various exposure pathways, including ingestion (via food and water) and inhalation. According to a study published in ‘Scientific Reports’, the total number of microplastics inhaled by a manikin over 24 hours reached up to 272 particles (L3S3) with an average concentration of 9.3 ± 5.8 microplastics per cubic meter of air. 

A pivotal study in the National Institutes of Health estimated that globally, humans might ingest between 0.1 to 5 grams of microplastics weekly through various exposure pathways. Translating this to an annual intake, the estimate ranges from 5.2 grams to 260 grams per year. However, comparing these figures to the weight of plastic bags requires a deeper understanding. 

To contextualize these numbers, let's compare them to the weights of common household items. A standard TV remote weighs between 100 to 200 grams, and a chess piece set weighs about 150-160 grams. If humans ingest up to 260 grams of microplastics annually, this equates to roughly 1.3 to 2.6 TV remotes or approximately 1.6 sets of chess pieces. This comparison provides a tangible sense of the amount of plastic ingested. 

The claim that humans ingest 50 plastic bags worth of microplastics annually is likely exaggerated. To illustrate this, consider that the weight of a typical plastic bag is around 5.5 grams. Ingesting 50 plastic bags would therefore amount to 275 grams of microplastics per year, which is within the higher range of the estimate but still extreme. 

The inhalation route has also been misrepresented in popular media. According to Full Fact, the claim that people inhale a credit card's worth of microplastics weekly is incorrect. A detailed analysis shows that the inhaled microplastic particles are significantly smaller than the dimensions of a credit card. For instance, fibres measured 177-237 nanometers in length and 26-30 nanometers in width, while fragments were 37-44 nanometers in diameter. Calculations indicate it would take over three and a half years to inhale a credit card's worth of microplastics, assuming continuous exposure in an indoor environment. 

It's important to note that these studies often simulate worst-case scenarios or competitive conditions. Not everyone is exposed to high concentrations of microplastics continuously, and factors like ventilation and outdoor time significantly affect actual inhalation rates. The author of the cited study noted that inhaling a credit card's worth would take thousands of years under typical conditions. 

The claim that humans ingest 50 plastic bags worth of microplastics annually appears to be a significant overestimation. Continuous research and more accurate assessments are essential to understand the true extent of microplastic exposure and its health implications. 

1. Simulating human exposure to indoor airborne microplastics using a Breathing Thermal Manikin. Scientific Reports. 

2. Full Fact. You do not inhale a credit card’s worth of microplastic every week. 

3. Estimation of the mass of microplastics ingested - A pivotal first step towards human health risk assessment. PubMed.