Occurrence, Degradation, and Effect of Polymer-Based Materials in the Environment

Abstract

There is now a plethora of polymer-based materials (PBMs) on the market, because of the increasing demand for cheaper consumable goods, and light-weight industrial materials. Each PBM constitutes a mixture of their representative polymer/sand their various chemical additives. The major polymer types are polyethylene, polypropylene,and polyvinyl chloride, with natural rubber and biodegradable polymers becoming increasingly more important. The most important additives are those that are biologically active, because to be effective such chemicals often have properties that make them resistant to photo-degradation and biodegradation. During their lifecycle,PBMs can be released into the environment form a variety of sources. The principal introduction routes being general littering, dumping of unwanted waste materials,migration from landfills and emission during refuse collection. Once in the environment,PBMs are primarily broken down by photo-degradation processes, but due to the complex chemical makeup of PBMs, receiving environments are potentially exposed to a mixture of macro-, meso-, and micro-size polymer fragments, leached additives, and subsequent degradation products. In environments where sunlight is absent (i.e., soils and the deep sea) degradation for most PBMs is minimal .The majority of literature to date that has addressed the environmental contamination or disposition of PBMs has focused on the marine environment. This is because the oceans are identified as the major sink for macro PBMs, where they are known to present a hazard to wildlife via entanglement and ingestion. The published literature has established the occurrence of microplastics in marine environment and beach sediments, but is inadequate as regards contamination of soils and freshwater sediments. The uptake of microplastics for a limited range of aquatic organisms has also been established, but there is a lack of information regarding soil organisms, and the long-term effects of microplastic uptake are also less well understood.There is currently a need to establish appropriate degradation test strategies consistent with realistic environmental conditions, because the complexity of environmental systems is lost when only one process (e.g., hydrolysis) is assessed in isolation. Enhanced methodologies are also needed to evaluate the impact of PBMs to soil and freshwater environments.

Microplastics Are Contaminants of Emerging Concern in Freshwater Environments: An Overview

“…It has been suggested that the term microplastics be redefined as items <1 mm to include only particles in the [40,41], and the term 'mesoplastic' introduced to account for items between 1 and 2,500 mm [42]. Lambert et al [8] described macroplastics as >5 mm, mesoplastics as 5 to >1 mm, microplastics as 1 mm to >0.1 μm, and nanoplastics as 0.1 μm. However, the upper limit of 5 mm is generally accepted because this size is able to include a range of small particles that can be readily ingested by organisms [42].…”

“…For instance, Carpenter et al [43], Colton et al [44], and Gregory [45] reported on marine plastics in the 1970s, but they have not been extensively studied particularly in the context of freshwater systems. As research focused on the issue more intensively since the early 2000s, MPs are considered contaminants of emerging concern [8,10,46].…”

“…On land littering is an important environmental and public issue [47,48] and is a matter of increasing concern in protected areas where volumes are influenced by visitor density; consequently, measures are now needed to reduce and mitigate for damage to the environment [49]. In addition, waste management practices in different regions of the world also vary, and this may be a more important source in one geographical region compared to another [8]. As with bulk plastic items, MPs can enter the environment by a number of pathways, and an important route in one geographical region may be less important in another.…”

“…To highlight this, a literature search on Thomson Reuters' ISI Web of Science returns 1,228 papers containing the term 'microplastic*', of which only a subset of 45 publications (3.7%) contains the term 'freshwater'. This has started to change in recent years, and attention is now also been directed towards both the terrestrial [8,9] and freshwater environments [8,10,11]. These publications point out the lack of knowledge for freshwater and terrestrial environments in terms of the occurrence and impacts of plastics debris.…”

Micro-and macro-plastics in marine species from Nordic waters

“…Additives are incorporated into plastics during plastic production although the quantities used vary greatly. It is estimated that additives account for around 4% of the total weight of plastics produced (Andrady & Neal, 2009;Lambert et al, 2014).…”