A study published in the journal Environment International finds traces of microplastic polymers in human blood. The sizes and shapes of polymers raise a serious concern over the possible risk of developing cardiovascular complications.
Study: Microplastics in human blood: Polymer types, concentrations and characterisation using μFTIR. Image credit: Shutterstock AI Generator
Background
Microplastics are synthetic plastic particles that can be found ubiquitously across multiple environments, including air, water, soil, and the food chain. Primary microplastics are produced intentionally for commercial use, which subsequently undergo a natural breakdown process (weathering) to generate secondary microplastics.
Recent evidence indicates the presence of microplastics in a variety of human tissues and organs, including lungs, colon, liver, placenta, breast milk, vein, and testis. Microplastics could enter the bloodstream primarily through inhalation and ingestion.
The size and shape of microplastics are the major determinants of their potential health hazards, including inflammation, oxidative stress, barrier disruption, genetic instability, reproductive complications, developmental and endocrine disorders, blood clot formation, and cardiovascular complications.
In this study, scientists have explored the types of microplastic polymers present in human blood and determined their size and shape using the micro-Fourier Transform Interferometer (μFTIR) microscopy technique.
Important observations
A total of 20 healthy individuals participated in this study. Blood samples collected from them were analyzed, which identified 24 polymer types in 90% of participants. Implementing the Limit of Quantitation (LOQ) threshold (lowest detectable concentration) approach resulted in the detection of microplastics in 40% of participants.
Among 24 identified polymers, five were above the LOQ threshold, including polyethylene (PE), ethylene propylene diene monomer (EPDM), ethylene–vinyl acetate/ethylene vinyl alcohol (EVA/EVOH), polyamide (PA), and ethylene–vinyl acetate (EVA).
Samples varied in the number of polymer types and concentrations. However, up to three polymer types were identified in a single sample. The most widely detected polymer type was PE, followed by EVA/EVOH, EPDM, PA, and EVA.
The highest concentrations of PE, EVA/EVOH, EPDM, PA, and EVA in a single sample were estimated to be 4.65 μg/mL, 1.84 μg/mL, 2.22 μg/mL, 1.84 μg/mL, and 0.61 μg/mL, respectively.
Characterization of microplastic polymers
The most abundant polymer types in blood samples were PE, EVA/EVOH, and EPDM, which accounted for more than 50% of all identified polymer types. The average length and width of identified microplastic particles were 127.99 ± 293.26 µm and 57.88 ± 88.89 µm, respectively.
About 88% of microplastics were categorized as fragments, and 79% were white or clear in appearance. However, a considerable number of fragments with different colors were identified in blood samples.
Several additive chemicals or plastic alternatives were identified in microplastic polymers obtained from blood samples.
Among identified additive chemicals, phthalates and tri (n-octyl, n-decyl) trimellitate were detected in 20% and 25% of blood samples, respectively. Other additive chemicals, including reacted alpha-olefin, trilauryl trithiophosphite, phosphate ester polyolefin, and 1,4-difluorobenzene-D4 were detected only in a single sample.
Another additive, 1-decanol, was detected in 60% of blood samples. Poly(3-hydroxybutyrate), a bacterial thermoplastic, biodegradable polyester-type plastic alternative, was detected in 20% of blood samples.
Study significance
The study identifies 24 different polymer types of microplastics in human blood samples. Polyethylene, ethylene propylene diene, and ethylene–vinyl-acetate/alcohol are the most abundant polymer types in blood samples.
Polyethylene is commonly used in packaging film, bags, bottles, toys, wire and cable insulation, and many household items. It is also used in medical implants. This polymer has previously been detected in human lung tissues and breast milk. Studies have linked polyethylene exposure with increased genetic instability.
Ethylene propylene diene is used in the automotive industry and artificial turfs. Fragments of this polymer have recently been identified in air samples collected from the rubber industry. To date, its presence has not been detected in any human tissues.
Ethylene–vinyl-acetate/alcohol is commonly used in food packaging, agricultural film, and the automotive industry. This polymer has previously been detected in human urine samples.
Microplastic particles identified in this study are significantly different in shape and larger in size than previously identified particles. Because of high flexibility, these large particles may enter in small-diameter blood capillaries. However, these particles may have a slow transit through capillaries, which in turn can facilitate their interactions with blood proteins for a longer duration.
The interaction between microplastics and blood proteins leads to the formation of a corona, which prevents the immune system's recognition of microplastics and subsequently increases the duration of microplastic exposure within the body.
Furthermore, microplastics with a non-linear structure could get stuck in capillaries, impairing blood flow and altering local oxygen concentration. These factors can collectively affect cell metabolism and functions.
Overall, the findings highlight the need for future studies to investigate the potential toxic effects of microplastics on human health.
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