Threat of Micro/Nanoplastics to Human Beings
It is well documented that plastic particles present in the ecological systems have the potential to affect human beings, directly or indirectly. The judgment of the micro/ nanoplastics hazard to human health requires an in-depth understanding of ecological plastics levels and pathways of exposure (Figure 1.4). Plastic particles present in the environment may reach individuals through inhalation of airborne particles, the digestive tract via food products (fish, drink products, beverages and canned food) and via dermal exposure. Micro/nanoplastic particles can also be consumed indirectly via personal care products such as toothpaste and scrubs or even cosmetics. Individuals may also be exposed to plastics through non-ecological resources such as prosthetics and biomedical treatments.
Approximately 50,000 to 15 million plastic particles are discharged into drinking water via various sources, and thus, it is the most common route of plastic exposure to humans . Food products and their packaging materials are another important source of plastic exposure to humans. Aquatic organisms are the major victims of micro/nanoplastic contaminants, either through water or the nourishing material; these organisms may serve as a cause of human plastic exposure. Translocation of microscopic plastic fragments across the gastrointestinal tract of crabs, fish and mussels is well reported [46,47]. Regarding bivalves, individuals eat the complete soft tissues which may include microscopic plastic fragments. Additionally, aquatic creatures may be polluted after collection during their storage and shipping. Human beings may also be directly exposed to micro/nanoplastic particulates from stored (typically weeks to months) food stuffs, which mainly includes harvested and processed animal and plant food items such as packed milk, beverages, vegetables and fruits. The physical existence of plastic particulates is toxic owing to their intrinsic ability to stimulate intestinal blockage or tissue abrasion. Additionally,
FIGURE 1.4 Pathways of micro/nanoplastics exposure causing hazards to human health.
tissue accumulation, kinetics and the dynamics pattern are mainly governed by micro/ nanoplastic particle size and morphology. Apart from the oral route, plastic exposure via dermal and inhalation routes is summarized in the sections below .