Microfibers as Carcinogenic and Neurodegenerative Agents

The microfibers are mainly released from the laundering of synthetic textiles, friction from the synthetic rubber tyres of running cars, and a variety of plastics such as polypropylene, polyethylene, polyester, polystyrene, polyvinylchloride, polyamide, polyethylene terephthalate, polyurethane, acrylonitrile butadiene styrene, etc. The factors that influence the harmful effects of the microfibers are routes of exposure, temperature, exposure concentration, and duration. Along with these are physico-chemical factors like type of fiber particles, shape and size, external charge, length-to-width ratio, porosity, and hydrophilicity. Inhalation or oral ingestion of these microfibers causes pulmonary ground glass nodules or lung cancer, angiosarcoma of the liver, acute myeloid leukemia, breast, prostate, stomach, and esophageal cancers. Microplastics act as carriers for toxic endocrine disruptor chemicals (EDCs) like bisphenol A (BPA), phthalates (PT) and phthalate esters (PTE), styrene (ST), acrylamide (AA), triclosan (TC), and brominated flame retardants (Br-FRs) and result in genetic changes and cancer. Microfibers also cause neurotoxicity by increasing dopamine levels and inducing oxidative stress. Oxidative stress shoots up the intracellular levels of reactive oxygen species (ROS), which can affect cellular metabolism by oxidative damage to proteins (of cell organelles, particularly the mitochondria and ER) and DNA, lipid peroxidation, cell membrane destabilisation, and subsequent cellular damage followed by cell death and neuro-inflammation. One of the major reasons for the occurrence of a number of neurodegenerative diseases like Alzheimer’s (AD), Parkinson’s (PD), Huntington’s (HD), and Amyotrophic Lateral Sclerosis (ALS) is the oxidative stress coupled with neuroinflammation in the central nervous system. Furthermore, microfibers inhibit acetylcholine esterase activity and alter neurotransmitter levels, resulting in behavioural changes. The surface of the microfiber is the best inhabitable place for most of the pathogenic bacteria and an adhesive surface for organic pollutants like polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCBs), and pesticides like dichlorodiphenyltrichloroethane (DDT), and hence, along with the microfiber, the pathogenic bacteria, organic pollutants, and pesticides may also contribute to the development of these disease conditions. This chapter covers essential aspects like the sources of microfibers, their physico-chemical nature, the entry of microfibers into human beings, and their role in the incidence of these diseases.