Review on COVID-19 biomedical waste-derived microplastic toxicity

By Pooja Toshniwal PahariaReviewed by Aimee MolineuxOct 11 2022

In a recent review published in Environmental Research, researchers reviewed existing literature on the biomedical waste (BW) source, elements, and the recent upsurge of microplastics (MPs) during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, as well as MP accumulation effects on aquatic and terrestrial organisms and human health.

During the coronavirus disease 2019 (COVID-19) pandemic, precautionary measures were implemented to curtail SARS-CoV-2 transmission, including the use of plastic-based PPE (personal protective equipment) The use of plastic bags, food containers, water bottles, and single-use plastic products significantly increased during the pandemic. COVID-19-associated BW explosion has threatened the global environment, terrestrial and aquatic organism health, and human health.

About the review

In the present review, researchers reviewed data emphasizing the recent increase in plastic-made BW, the transformation of BW to MPs, the detrimental impacts of MPs on human health and other environmental organisms, and biomarkers for MP-associated health hazards.

BW sources, elements, and transformation

BW during COVID-19 comprises PPE equipment (protective suits, hand gloves, eye shields, face shields, face masks, goggles, and gum boots), pharmaceutical waste (syringes, intravenous bags, medical and plastic bottles) and general waste (single-used plastic, toothbrushes, plastic bags, kitchen waste, and wrappers).

Masks, face shields, and eye shields comprise polypropylene (PP), polycarbonate (PC), and polystyrene (PS), whereas gowns are made up of low-density polyethylene (LDPE). Hand sanitizer bottles, aprons, gloves, and goggles are made up of polyvinyl chloride (PVC). Packaging materials comprise PP, PS, LDPE, high-density PE (HDPE), and polyethylene terephthalate (PET), and plastic bottles are mainly made up of PET and PP.

Biomedical wastes disposed into the soil, water, or air form plastic polymers reacting with hazardous elements in the three environment matrices. Water contains cadmium, zinc, lead, and copper, whereas soil comprises mercury, chromium, silver, lead, cadmium, and chromium. In addition, soil contains salts of aluminum, calcium, iron, potassium, and sodium.

Air may contain pathogenic bacteria, dioxin and furan (after incineration), particulate matter, metals, acid gases, oxides of nitrogen, and sulfur. The polymers eventually convert into MP monomers by biological (biodegradation), or non-biological (oxidative degradation, wave and turbulence, and ultraviolet rays) processes.

Effects of MP accumulation in organisms

MP accumulation in daphnia (Daphnia magna) causes immobilization, and in microalgae (Tetraselmis chuii) it causes lower growth rates and chlorophyll content. In algae (Chlorella pyrenoidosa), diatom (Skeletonema costatum), and beans (Vicia faba), MPs reduce photosynthesis, reduce growth, and increase genotoxicity and oxidative damage, respectively.  In blue mussels (Mytilus edulis), MPs cause deformities, and in oysters (Crassostrea gigas), MPs can reduce oocyte counts and sperm velocity. MPs reduce Oryzias melastigma fecundity, larvae, and fish lengths and weights, and enhance mortality.

In zebrafish (Danio rerio), MPs cause inflammation, lipid accumulation, altered liver metabolomics, metabolism-associated genetic derangements, and significant larvae transcriptome altercations. In red tilapia (Oreochromis niloticus), MCs inhibit cranial acetylcholinesterase activity. In other wild fish species, MPs enhance lipid peroxidation in the brain, gills, and dorsal muscles and stimulate cranial acetylcholinesterase activity. In mice, MPs cause lipid and gut microbiome alterations, elevate hepatic oxidative stress, and reduce adenosine triphosphate (ATP) and acetylcholinesterase levels.

Health implications and biomarkers of MP accumulation in humans

MPs pose a severe threat to human health. MPs could enter the human body indirectly from terrestrial and aquatic organisms and accumulate in human tissues, leading to reactive oxygen species (ROS) generation and increased oxidative stress. As a consequence, cell membrane damage, deoxyribonucleic acid (DNA) strand breaks, disruption, mitochondrial damage, and elevated levels of pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-a) occur.

Concerning the digestive system, MPs can reduce nutrient consumption and metabolism and inhibit cell viability, pro-inflammatory responses, and morphological changes. They can alter gut microbiota and increase bowel permeability. MP accumulation may lead to colorectal cancer. MP accumulation in respiratory tissues could cause genotoxic and cytotoxic effects on pulmonary epithelial cells and macrophages, with increased inflammation, oxidative stress, cell damage, and size-associated toxicity.

Increased particle translocation, immune modulator release, and immune cell activation resulting in self-antigenation and autoantibody formation could also occur. As a result, chronic disorders such as asthma, chronic pneumonia, allergic alveolitis, chronic bronchitis, pneumothorax, and lung cancer could develop. MP accumulation in cardiovascular tissues could lead to cytotoxicity, autoimmune reactions, rapid hemolysis, hypertension, vascular occlusion, and increased coagulability.

Increased MP-associated toxicity, mutagenicity, and cancer could develop in reproductive tissues. In endocrinal tissues, MPs could alter testosterone and other hormonal levels, affect adipose tissue receptors and increase mammalian prostate and breast cancer risks. MP accumulation in the immune system could result in autoimmune rheumatism, systemic lupus erythematosus (SLE) and reduced protective immune responses. Further, MPs could elevate Alzheimer’s disease and dementia risks.

Overall, the review findings highlighted BW sources, elements, and transformation into MPs, and the impacts and biomarkers of increased MP generation during the COVID-19 pandemic on terrestrial and aquatic organisms and human health.