Microplastic sources, formation, toxicity and remediation: a review

Abstract

Microplastic pollution is becoming a major issue for human health due to the recent discovery of microplastics in most ecosystems. Here, we review the sources, formation, occurrence, toxicity and remediation methods of microplastics. We distinguish ocean-based and land-based sources of microplastics. Microplastics have been found in biological samples such as faeces, sputum, saliva, blood and placenta. Cancer, intestinal, pulmonary, cardiovascular, infectious and inflammatory diseases are induced or mediated by microplastics. Microplastic exposure during pregnancy and maternal period is also discussed. Remediation methods include coagulation, membrane bioreactors, sand filtration, adsorption, photocatalytic degradation, electrocoagulation and magnetic separation. Control strategies comprise reducing plastic usage, behavioural change, and using biodegradable plastics. Global plastic production has risen dramatically over the past 70 years to reach 359 million tonnes. China is the world's top producer, contributing 17.5% to global production, while Turkey generates the most plastic waste in the Mediterranean region, at 144 tonnes per day. Microplastics comprise 75% of marine waste, with land-based sources responsible for 80-90% of pollution, while ocean-based sources account for only 10-20%. Microplastics induce toxic effects on humans and animals, such as cytotoxicity, immune response, oxidative stress, barrier attributes, and genotoxicity, even at minimal dosages of 10 μg/mL. Ingestion of microplastics by marine animals results in alterations in gastrointestinal tract physiology, immune system depression, oxidative stress, cytotoxicity, differential gene expression, and growth inhibition. Furthermore, bioaccumulation of microplastics in the tissues of aquatic organisms can have adverse effects on the aquatic ecosystem, with potential transmission of microplastics to humans and birds. Changing individual behaviours and governmental actions, such as implementing bans, taxes, or pricing on plastic carrier bags, has significantly reduced plastic consumption to 8-85% in various countries worldwide. The microplastic minimisation approach follows an upside-down pyramid, starting with prevention, followed by reducing, reusing, recycling, recovering, and ending with disposal as the least preferable option.

Keywords: Biodegradable plastics; Microplastic control; Microplastic detection; Microplastic pollution; Microplastic toxicity; Water treatment.

Fig. 1

Microplastic effects and pathways on the environment and human health. Microplastics' formation is detectable in several biological samples. Microplastic has toxicological effects, necessitating the implementation of treatment technologies. The cycle of microplastic ingestion ends primarily in seafood and its associated health problems. UVA, UVB, and UVC are different ultraviolet (UV) radiation types. UVA has the longest wavelength, is the least energetic, and is the most common type of UV radiation. UVB has a medium-range wavelength and is more energetic than UVA. UVC has the shortest wavelength and is the most active type of UV radiation

Fig. 2

Different classifications of microplastics. Microplastics can be classified into two categories: primary microplastics and secondary microplastics. Primary microplastics are intentionally manufactured and added to consumer and commercial products like cosmetics, personal care products, pharmaceuticals, detergents, and insecticides. Secondary microplastics, on the other hand, are unintentionally formed by the breakdown of larger plastic materials through physical, chemical, or biological processes, such as fishing gear, plastic bottles, plastic bags, and plastic food containers. Microplastics can also be classified based on their chemical composition, which includes polyethylene, polypropylene, polystyrene, and other materials

Fig. 3

Life cycle of microplastics in the environment. The discharge resulting from diverse activities flows into aquatic systems, introducing microplastics into the food chain and their subsequent bioaccumulation in the tissues of aquatic organisms. This accumulation can result in significant adverse effects on the aquatic ecosystem, and these effects can be directly transmitted to humans and birds

Fig. 4

Land-based and ocean-based microplastics' sources. Land-based sources contribute 80–90% of microplastics to water bodies, which include plastic bags, plastic bottles, personal care products, plastic incinerators, construction materials, and textiles. Ocean-based sources contribute 10–20% of microplastic discharge into water bodies, mainly marine vessels, plastic litter on beaches, and fishing gear

Fig. 5

Detrimental effects of microplastic ingestion on human health and toxic mechanisms. Microplastics found in everyday items, including bottle packaging, can have harmful effects on human health when ingested. Once absorbed through the intestines, they can travel through the circulatory system to other organs. Different mechanisms can take microplastics, such as membrane damage, clathrin/caveolin-dependent, caveolin-dependent, clathrin-dependent, and micropinocytosis. High levels of microplastics can increase oxidative stress, producing inflammatory cytokines, apoptosis, cytotoxicity, and gene expression disturbances

Fig. 6

Plastic minimisation strategies. Strategies begin with prevention as the most favoured option a. Reuse, recycling, and recovery are other waste minimisation strategies. Disposal is the least favoured waste minimisation strategy. The 7 R’s waste minimisation approach includes recovering, repairing, reusing, reducing, re-gift, refusing, and rethinking b