Rachel Carson’s Silent Spring  (1962) goal of a toxics-free future seems a very distant prospect.

By juli 19, 2023 Algemeen

Novel entities are defined as new substances, new forms of existing substances and modified life forms, including chemicals and other new types of engineered materials or organisms not previously known to the Earth system as well as naturally occurring elements (for example, heavy metals) mobilized by anthropogenic activities. Novel means new in the geological sense, that is, created, introduced, or recirculated by humans. The entities are intentionally and unintentionally manufactured chemicals, engineered materials, and their transformation products, that have the potential to cause effects on vital Earth System processes as well as naturally occurring elements and materials mobilized in new ways, new forms, or at substantially higher rates by anthropogenic activities. The production of intended chemicals entails the unintended production of byproducts, transformation products, and impurities which may not be considered under chemicals assessments and management measures.

Earth System processes are the biophysical processes that together determine the self-regulating capacity of the planet, that is, the interacting physical, chemical, and biological processes on land, in the oceans, and in the atmosphere. Earth has a finite assimilative capacity for chemicals introduced into the environment by humans, especially the toxic, persistent, bioaccumulative, and easily mobilized chemicals.

This innocuous-sounding boundary encompasses all of the toxic and long-lived substances that humanity releases into the environment, which individually or in aggregate threaten the stability of the whole Earth system. The most terrible dilemma connected with this little-known but vast seething toxic legacy: humanity has almost no idea of how close it presently is to catastrophically crossing this unseen border, as it continues to regularly dump synthetic chemicals, pesticides, heavy metals, radioactive waste, genetically modified organisms, and nanoparticles randomly into the environment. A big unknown is how the cocktail of novel entities may interact with each other and the environment to inflict additive, or even multiplicative, unpredictable damage on Earth systems.

Plastics are a novel entity in their own right: Ubiquitous, mobile, and exceptionally slow to degrade, plastics may be the fastest-growing threat to Earth systems. Plastic debris in the environment can pick up other pollutants and distribute them far and wide, making microplastics the nexus for a lot of other environmental issues. They absorb all sorts of really toxic, human-health-impacting chemicals like polyaromatic hydrocarbons and polychlorinated biphenyls, and they incorporate flame retardants and PFAS. An emerging area of novel entities research concerns nanoparticles. At the nanoscale, the properties of familiar elements and molecules can change in unpredictable ways. These tiny particles, each less than a thousandth the width of a human hair, are generated by a wide variety of processes, both natural and fabricated, including forest fires and wood-burning stoves, road traffic pollution, and many high-temperature industrial processes. Once inhaled, nanoparticles can access our vital organs. For example, because they’re so small they can go straight up your olfactory nerves and into the brain. In addition to the countless nanoparticles we are unwittingly releasing into the environment as a byproduct of human activities, nanotechnology is also creating entirely new types of nanoparticle.

Microplastics exist in different forms in the environment and generally occur in the size of less than 5 milli meters. Microplastics have been found on the slopes of Everest, at the bottom of the Mariana Trench in the Pacific Ocean, in tap water and bottled water, soft drinks and beer, and they are inside living creatures, including us. They are classified as primary and secondary whether they are manufactured in microscopic size, or acquired from the breakdown of larger plastics, respectively. Primary microplastics are plastic pellets that are manufactured in microscopic size to be used in the plastic industry, personal healthcare products, such as facial cleansers and cosmetics. Secondary microplastics are obtained, due to deterioration of larger plastic debris by photooxidative, thermal, chemical degradation and/or mechanical abrasion. The degradation rates of plastic wastes present in environment is much slower, and even a single plastic bag will take thousands of years to get completely removed. Per- and polyfluoroalkyl substances (PFAS) are a large class of thousands of synthetic chemicals that are used throughout society. However, they are increasingly detected as environmental pollutants and some are linked to negative effects on human health. They all contain carbon-fluorine bonds, which are one of the strongest chemical bonds in organic chemistry. This means that they resist degradation when used and also in the environment. Most PFAS are also easily transported in the environment covering long distances away from the source of their release. PFAS compounds are used in food packaging (even some marketed as compostable), cookware, textiles, cosmetics, electronics, and industrial firefighting foams. These highly toxic chemicals easily migrate into the air, dust, food, soil and water. Polymeric substances are one of the major building blocks that decides the chemical structure or properties of a particular microplastic particle. The polymers, such as polypropylene (PP), polyethylene (PE), polypropylene ether (PPE), polyethylene terephthalate (PET), polyester (PS) are some of the predominant ones that are extensively found, when studying the chemical composition of microplastics. Not only the polymers that are being used in microplastics, but also the chemical additives, which are used to improve their structural properties, also contribute to toxic effects in living organisms during their leaching by weathering. The fate and transport of microplastics are greatly determined by their physico-chemical properties. Size, one of the important physical properties of microplastics is found to have direct association with the biological responses of, by example, the aquatic organisms.

Persistent, manufactured or processed solid material discarded, disposed of, or abandoned on the coastline or in the sea, marine litter is currently considered a major threat to the marine environment. Around 80% of the marine debris originates from numerous land-based sources such as poorly managed burials in landfills, untreated sewage, inadequate industrial control, recreational use of coastal areas, and tourist activities. These materials can be transported to water bodies via storm drains, rivers, and weather events.

Microplastics introduced into marine environment through anthropogenic activities have become a global concern, posing serious impacts. Detection of high concentrations of microplastics even in restricted areas of sensitive ecosystems, such as mangroves and coral reefs shows an alarming signal that more focus is needed towards this emerging threat. The transfer of microplastics through different trophic levels of the marine food chain shows their increased bio accumulative potential. The presence of plastic particles, is one of the most urgent issues to be addressed by society. Several factors such as polymer, size, shape, presence of additives, and age and type of organisms may yield a considerable variation of effects, making the risk assessment of plastics a difficult task. Nonetheless, it is clear that the presence of small plastic particles affects biota directly or by modulating the effects of other environmental contaminants.

Microplastics, are a global threat of the marine ecosystem. Microplastics exist in different forms in the environment, and generally occur in the size of less than 5 milli meters. They are classified as primary and secondary whether they are manufactured in microscopic size, or acquired from the breakdown of larger plastics, respectively. Primary microplastics are plastic pellets that are manufactured in microscopic size to be used in the plastic industry, personal healthcare products, such as facial cleansers and cosmetics. Secondary microplastics are obtained, due to deterioration of larger plastic debris by photooxidative, thermal, chemical degradation and/or mechanical abrasion. The degradation rates of plastic wastes present in environment is much slower, and even a single plastic bag will take thousands of years to get completely removed. Polymeric substances are one of the major building blocks that decides the chemical structure or properties of a particular microplastic particle. The polymers, such as polypropylene (PP), polyethylene (PE), polypropylene ether (PPE), polyethylene terephthalate (PET), polyester (PS) are some of the predominant ones that are extensively found, when studying the chemical composition of microplastics. Not only the polymers that are being used in microplastics, but also the chemical additives, which are used to improve their structural properties, also contribute to toxic effects in living organisms during their leaching by weathering. Implication of additives of biological origin, instead of commercially applied additives may decrease the aquatic toxicity. The fate and transport of microplastics are greatly determined by their physico-chemical properties. Size, one of the important physical properties of microplastics is found to have direct association with the biological responses of the aquatic organisms. Microplastics were readily ingested by the daphnids (small planktonic crustaceans), since their food preferences are usually in this size. After ingestion by such planktonic crustaceans, due to their micro sized levels and higher retention properties, microplastics easily translocate within their body, and affect their dynamic way of food ingestion and their regular physiological activities. As these planktons are vital in maintaining the food chain of marine and coastal mangrove ecosystems, accumulation of microplastics within them can get transferred to higher trophic levels. A study determined the factors affecting microplastics ingestion in fishes stated that clupeids had the highest concentrations of microplastics within their body. One of the major reasons could be that these fishes were planktivorous in nature, and consuming planktons that have ingested microplastics or microplastics that were in the similar size to that of planktons, as their major feed could have led to higher toxic effects. Depending upon the sources of contaminations, the size of microplastics in aquatic samples obtained from different regions varied. In general, the dominant form of microplastics that were observed in marine organisms, were majorly in the form of microfibers or fragments that might have resulted from fishing nets being used. The shape of the microplastics present in the aqueous systems may be regular or irregular, and can indirectly affect various other properties, such as density of microplastics. For example, when present in their fibrous form or as films, the buoyancy would be higher, and they hardly settle in water, and are more available or exposed to the aquatic community in all subsurface of the marine system. Rather when present in the form of spherical particles, their chances of settleability or sedimentation would be comparatively higher. When studying the ecotoxicological effects of microplastics in different coastal systems, found that non spherical particles showed a higher risk of toxicity effects than spherical ones, and were found in abundance in the coastal waters than open seawater. Color of the microplastics is another physical property that affects the rate of ingestion by different trophic levels. Dark colored microplastics, such as blue, black, and green were ingested in more amounts by the fish community than light colored microplastics, and this may be because of their attractive nature or the similarity in color with that of their original preys. Despite these reasons, the chemicals that have been used to provide bright colors to the polymeric substances are found to pose secondary toxic effects in aquatic systems. Dark colored microplastics especially black were present for about 16%, followed by red within the shrimp body, and it may be because of their visual similarity to that of their prey. Other than physical properties, the surface properties of microplastics when coated with industrial chemicals, make them act as carriers for transporting toxic metals, such as rare earth metals and other pathogenic organisms to enter food chain through adsorption-diffusion mechanisms. Hence, physico-chemical properties of microplastics, such as size, shape, color, polymeric composition, and chemical additives have a vital role in deciding their fate, transport, and extent of toxicity in various organisms.

The deepest part of the ocean, 11,000 metres deep, is 50 times more toxic than the most toxic rivers in China. We know almost nothing about the Abyss and the importance of marine life and ocean currents that circulate water around the world at depth and at the surface. Humanity has caused so much pollution that the Abyss is now more toxic than most rivers.
We are killing the ocean surface with floating toxic chemicals, plastic, and partially combusted carbon. The waste that sinks now covers most of the world’s oceans, including the deepest parts. When industry starts deep-sea mining, this toxic soup is going to be kicked up into the upper layers, with potentially catastrophic consequences.

Most evidence on the effects of plastics on the environment comes from aquatic ecosystems but there is increasing evidence that plastic pollution is affecting plants and soil as well. However it is not yet clear the extent to which plastics have actually entered terrestrial food webs – and this is where our new research comes in. Soil animals may be minute but there can be tens or hundreds of thousands of them per square meter of soil. These high numbers mean that soil animal may transport and thoroughly redistribute fragments of microplastics through the entire length and depth of the soil. As both microplastics and small but very numerous soil animals are found everywhere, this redistribution of plastics could be a global process.

Urbanization is one of the main reasons for introducing microplastic contamination into water sources. Countless number of sources, such as wastewater treatment effluents, industrial discharges, leachate from landfills, household decors, etc., can directly introduce high concentrations of microplastics into freshwater and marine ecosystems. Many hydrological and meteorological parameters, such as rainfall, food, runoff affects their spatial and temporal distribution within water systems and decides the mobilization of their concentrations. The increase in microplastic load in wastewater treatment effluents may be due to accumulation of consumer products.

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