River plumes
1.15.2 Human Health Effects
Microplastics are ubiquitous environmental contaminants that lead to inevitable human exposure (69). The evidence for potential negative effects of microplastics in the human body has been reviewed. The study focuses on the pathways of exposure and toxicity.
Exposure may occur by ingestion, inhalation and dermal contact due to the presence of microplastics in products, foodstuff and air. In all biological systems, microplastic exposure may cause particle toxicity, with oxidative stress, inflammatory lesions and increased uptake or translocation. The inability of the immune system to remove synthetic particles may lead to chronic inflammation and increase risk of neoplasia. Furthermore, microplastics may release their constituents, adsorbed contaminants and pathogenic organisms. Nonetheless, knowledge of microplastic toxicity is still limited and largely influenced by exposure concentration, particle properties, adsorbed contaminants, tissues involved and individual susceptibility (69).
1.15.3 Recycling
Recycling has been recognized as the preferred plastic waste management solution. However, little is known about the detailed characteristics of plastic waste and how these may affect its recycling (85).
In a study, hard plastic, plastic film and poly(vinyl chloride) (PVC) waste collected at three Danish recycling centers were sampled and characterized according to product applications, legislative requirements (quality), expected product lifetime, polymer types and presence of potential impurities such as colored plastics, non-plastic materials and multi-polymer products (85).
The so obtained information was used for the estimation of overall recycling potentials for selected archetype recycling process chains based on material flow analysis. In addition to providing detailed data for the composition of the plastic waste products, the results showed that impurities represented 28% (wet weight) of the plastic waste, and that about 75% of the plastic waste was characterized as low-quality applications, indicating some legislative recovery restrictions. By accounting for the level/type of impurities, the overall recycling potential was found to be 52% for hard plastics, 59% for plastic films and 79% for PVC waste.
The results of the study showed that while varying according to polymer type, the recyclability of high-quality plastic waste was 12% – 35% higher than low-quality applications. While actual results are representative of Danish conditions, the study demonstrated that detailed characteristics of plastic waste are needed to identify potential challenges to recycling, thereby potentially improving the design and the efficiency of recovery of recycling facilities (85).
In Europe’s Nordic region, there is low utilization of plastic waste and only a fraction of plastic materials goes back into production processes through reuse and recycling practices (86). In the main hotspots identified, these processes are in low demand due to price considerations, insufficient traceability and transparency in value chain transactions, and general design deficiencies in the recyclability of products.
1.15.3.1 Pollution Control
Plastics have been reported as one of the major pollutants among various pollutants that are disposed of in the environment (87). They play a pivotal part in human life as they are cost-effective and versatile.
Plastics are known to contain a mixture of many chemical components and are used for various domestic applications. Despite various useful applications, plastics take a long time to degrade.
The burning of plastics releases chemicals, such as phosgene and dioxides, that are considered a hazard to the ecosystem. The toxic debris that is released from the plastics can enter the food chain and water bodies in the form of microplastics.
Microplastic-polluted foods and the presence of meager amounts of phthalates in toys lead to serious health consequences such as congenital diseases and malignant cancers. The dioxins released from the plastic polymers are lethally persistent organic pollutants which cause tumor and neurological damage in humans.
Inadequate waste management practices have led to significant plastic pollution of water bodies (87). Plastics tend to settle on beaches, which decreases esthetic and recreation values. This article discusses methods for resource recovery from plastic wastes and the possible effects of plastics on the environment and available safety regulations for the use of plastics.
The scientific literature about the remediation of plastics using various methods has been discussed, which can help to promote further improvement of the existing system by competent authorities and researchers (87).
1.15.3.2 Bioplastics
Growing environmental concerns associated with the accumulation of plastic waste in the natural environment have incentivized considerable research into renewable alternatives, and more recently, alternative waste management strategies (88).
To mitigate growing environmental concerns, while simultaneously facilitating an increase in plastic demand, it is imperative that the polymer industry evolves, shifting its focus from single-use and disposable plastics to a model focused on recapturing product value and reducing waste, namely the circular economy (89–91).
The issues of PLA, a bioplastic, and recent research within the field of recycling have been reviewed (88). Attention has focused on the research surrounding plastic waste management. Various end-of-life options available to plastics were discussed more broadly, before presenting the existing technologies, challenges and future opportunities for PLA. Herein, all waste management strategies presented for PLA are discussed within the context of industrial feasibility (88).
1.15.3.3 Steam Cracker
A number of processes have been described for converting plastic waste into products for further processing such as catalytic or thermal processes, hydrocracking processes, extrusion processes, etc. For example, a process has been described where plastic waste is converted into lower hydrocarbons (92). This entails the plastic waste being reacted in a fluidized bed apparatus at about 300°C to 630°C. The resulting lower hydrocarbons, such as paraffins or waxes, can be converted by means of steam cracking into olefins. Plastic waste can be converted by the combination of fluidized bed apparatus and a known steam cracking process into these olefins.
An evident disadvantage of this process is that for the steam cracking process it is necessary to add naphtha to the feed materials obtained, i.e., it is not possible to convert the plastic waste into cracked products such as ethylene, propylene, etc., without adding traditional feed materials. Furthermore, the handling of the solids in the fluidized bed always proves to be a disadvantage. It is also problematic to scale up a process of this type to a large-scale industrial operation.
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