Microplastics Exposure Routes and Toxicity Studies to Ecosystems: An Overview

Abstract

Plastic products with tremendous consumption are ubiquitous in our daily lives and the annual production of plastics is drastically increasing [1]. It is now expected to reach 33 billion tonnes by 2050 [2] with plastic waste in the environment projected to reach 67.8 million metric tons by the same year [3]. The pollution of plastic cum microplastics (MPs) from degradation in the environment is currently a hot issue attracting the global attention of many scientists, governmental and non-governmental organization and the public media [3-7]. Although few studies have investigated the chemical behavior and toxicity of MPs in the natural environment, studies focusing on its toxicity in tandem with toxic chemicals to ecosystems are scarce [1,4,8]. There are many toxicology reports that MPs are harmful to ecosystems. Terrestrial organisms such as earthworms, soil collembolans, and other animals, as well as plants have been affected by MPs [1,4,9-13]. Also, aquatic organisms such fish, sandhoppers, sea turtle, crustacean and mussel have also been affected by MPs [14-15]. In addition, humans are exposed to MPs via trophic transfer or by direct ingestion, contact and inhalation and plausible effects include lung inflammation and genotoxicity may occur [1,3,16,17]. Aside from the innate toxicity of MPs, they can carry different toxic chemicals such as heavy metals and organic pollutant by adsorption process, and double the effect of such pollutants [1,8,18]. Succinctly, plastic products are made up of mixtures of polymers, fillers, and multiple additives to improve its usability. Also, there are other chemicals including unreacted monomers, starting substances and non-intentionally added substances (NIAS; impurities, side or breakdown products) that are also present in plastic. However, most of these chemicals are not covalently bound to the polymer, so they can be released at all stages of the plastics' life cycle via migration to liquids or solids or via volatilization [1]. Therefore, plastic materials are an important source of human exposure to chemicals.

In silico binding affinity analysis of microplastic compounds on PET hydrolase enzyme target of Ideonella sakaiensis

“…These properties also present the key problem with plastic waste being persistent in the environment and so many countries have tried to reverse the situation by banning single-use and encouraged recycling of waste plastics (Verla et al 2019a, b). Current data suggests that 10% of plastic produced annually ended up as waste in the environment (Enyoh et al 2020). Some plastic materials found in the environment include polypropylene (PP), polycarbonate (PC), expanded polystyrene (PSE), polyarylsulfone (PSU), polystyrene (PS), thermoplastic elastomers (TPE), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polypropylene (PP), polyamides (PA), fluoropolymer, etc.…”

“…Plastic pollution can lead to the death of big sea animals such as whales, turtles, etc. from Open Access Duru et al Bull Natl Res Cent (2021) 45:104 ingestion or entanglement (Enyoh et al 2020). Plastics often distribute organisms to areas that are less biologically diverse and not their original habitat as they are transported by wind and ocean current.…”

“…Plastics could be broken down by the action of light or mechanically into smaller size particles called micro (MPs: 0.1 µm to < 5 mm) and nano (NP: < 100 nm) plastics and pose further threat to the ecosystems. The primary risks of MPs and NPs to the ecosystems are their ubiquity and bioavailability for ingestion, entanglement or inhalation (Enyoh et al 2020). There are multiple reports of their ingestion by marine, soil organisms and plants from polluted soils (Li et al 2019).…”

Microplastics from degradation of tires in sewer networks of the city of Riobamba, Ecuador

“…considered as secondary MPs, since they come from the decomposition and fragmentation of a macroplastic that is the tyre [22]. Any type of microplastic or macroplastic structure presents a great risk to the health in animals and people [5]. Even more when a city like Riobamba does`n have a water treatment plant.…”

“…The problem is that these materials are toxic, abrasive and difficult to treat due to their small size. [5]. But the question that science must still answer is from what amount ingested plastic can be a problem for human health.…”