Dermal Route

Dermal contact may take place when an individual interacts with water polluted with micro/nanoplastic particulates during bathing, washing or via facial/body scrubs containing micro/nanoplastic particulates. However, owing to size of micro/nanoplastic particles, their uptake across skin needs penetration through stratum corneum, which is limited to particles below 100 nm, so absorption via the skin is unlikely to arise. Yet, nanoplastic could easily penetrate into the human skin. Additionally, the excess use of cosmeceuticals or personal care products may also causes harm to human skin [48,49].

Inhalation

Lungs are constantly exposed to surroundings and thus prone to injury caused by pollutants and oxidative stress [48,50]. Human exposure to plastic particulates via the inhalation route could happen after micro/nanoplastics become airborne, typically from wave action in marine environments or during wastewater treatment. Additionally, fragmented fibers microplastics are readily present in polluted air. These fibrous microplastics have the ability to carry harmful pollutants, carcinogens, chemicals and gases. Most of these inhaled fibrous microplastics act as bioperspirants, and their deposition and clearance vary according to their respective concentration, dimensions and morphology. Most of them are subjected to mucociliary clearance; however, a few may persist in the pulmonary airways causing inflammation and other localized biological responses. Overall biological response may worsen, especially for individuals suffering from lung disease. Additionally, these contaminants lead to health effects such as genotoxicity, carcinogenicity and mutagenicity [48,51].

Harmful biological effects from micro/nanoplastic particles may result from a combination of the plastics’ inherent properties such as chemical composition, synthetic additives, leaching of components, ability to initiate chemical reactions and, mainly, the non-biodegradable nature. So far, various in vitro studies are carried out to highlight toxicity of micro/nanoplastic particles toward human health. Yet, only a few studies are reported using in vivo dynamics on plastic [52,53]. Owing to its non-biodegradable nature and chemical composition, it is known to initiate several cellular damages such as alterations of the lysosomal compartment, downregulation of immunological responses, initiation of peroxisomal proliferation and disruption of the antioxidant system. All these consequences may cause an altered gene expression profile and subsequently instigate genotoxicity, mutagenicity and neurotoxicity. Recently, few researchers reported that micro/nanoplastic particles could also act as a vector for pathogens, causing potential distribution in species and disturbing the ecology [54]. It also causes bioaccumulation and dispersion of contaminants across the ecosystem, ultimately threatening human health [48]. Overall, the estimation and isolation of micro/nanoplastic elements from the ecological matrices is a very essential task. Therefore, upcoming investigations should assess and understand the fate of plastic elements with their allied chemicals through the food chain.

 
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