The more we destabilize the processes and systems that maintain the stability and resilience of our planet, the more our civilization is at risk. For millions of years temperatures on Earth have changed, significantly, there have been extinction events, but the planet it still here. During those millions of years, it’s our civilization that wasn’t there. Our world as we know it, including all of its history, goes back only about 12000 years. And this period has been characterized by a miraculously stable climate, that has allowed for the development of the agriculture, cities, economies and human societies that we know. . Despite some natural environmental fluctuations over these past 12000 years (e.g., rainfall patterns, vegetation distribution, nitrogen cycling), Earth has remained within the Holocene stability domain. The resilience of the planet has kept it within the range of variation associated with the Holocene state, with key biogeochemical and atmospheric parameters fluctuating within a relatively narrow range.
These rapid changes to the Earth system undermine critical life-support systems, with significant societal impacts already felt and they could lead to triggering tipping points that irreversibly destabilize the Earth system. Our civilization on the planet, our viability as a society. But it’s not just about human civilization. The human-only perspective ignores the rest of the life forms we are driving to endangerment or extinction alongside our own species. We do not understand the complete scope and scale of the Sixth Extinction, but it is human-caused, and it is significant. It is about accelerated rates of decline and extinction of other species, the collapse of natural ecosystems and disruption of ecosystem processes.
There are the non-negotiable planetary preconditions that humanity needs to respect in order to avoid the risk of deleterious or even catastrophic environmental change at continental to global scales. Understanding how biosphere, anthroposphere, and geosphere processes interact with one another is a prerequisite for developing reliable projections of possible future Earth system trajectories. A fully process-based understanding of the interactions between these domains is, however, still only partially available. The planetary boundaries framework calls for more deeply integrated modeling of Earth system by bringing together currently available evidence for the relevant processes and their interactions from different disciplines and sources.
Transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental- to planetary-scale systems. The relevant to Earth’s overall state identified nine planetary boundaries represent components of Earth system that are critically affected by anthropogenic activities. They cover the global biogeochemical cycles of nitrogen, phosphorus, carbon, and water; the major physical circulation systems of the planet (the climate, stratosphere, ocean systems); biophysical features of Earth that contribute to the underlying resilience of its self-regulatory capacity (marine and terrestrial biodiversity, land systems); and two critical features associated with anthropogenic global change (aerosol loading and chemical pollution). The boundaries for climate change, biosphere integrity, biogeochemical cycles, land system change, fresh water and novel entities, which includes plastic and other human-made chemicals.
Let’s focus on a new entry; novel entities. The definition of this boundary is now restricted to truly novel anthropogenic introductions to Earth system. These include synthetic chemicals and substances (e.g., microplastics, endocrine disruptors, and organic pollutants); anthropogenically mobilized radioactive materials, including nuclear waste and nuclear weapons; and human modification of evolution, genetically modified organisms and other direct human interventions in evolutionary processes. Hundreds of thousands of synthetic chemicals are now produced and released to the environment. For many substances, the potentially large and persistent effects on Earth system processes of their introduction, particularly on functional biosphere integrity, are not well known, and their use is not well regulated.
Let’s go a bit deeper! Plastics are a major environmental and global hazard, responsible for the majority of pollution accumulation and have spread across marine, freshwater, and terrestrial ecosystems. The impact and scale of plastic pollution on ocean species and ecosystems cannot be underestimated. Negative impacts from plastic pollution are already detectable in most species groups while the productivity of several of the world’s most important marine ecosystems, like coral reefs and mangroves, are under significant risk.
Microplastics are ubiquitous and originated from various anthropogenic sources. Microplastics (size range 1 μm–5 mm) and nanoplastics (NPs; size range 1 nm–1 μm) are emerging plastics-related environmental pollutants, having a major ecotoxicological concern to humans and many other biotas, especially aquatic animals. Based upon their sources, microplastics can be categorized into primary micro-nanoplastics, manufactured for indirect or direct use as raw materials for consumer polymer goods, and secondary micro-nanaoplastics produced from the breakdown, cracking, and progressive deterioration of larger plastic fragments, so the concentration of micro- and nanoplastics will continue to increase for decades.
Microplastics are the result of the glut of plastic pollution that is choking our lands and oceans. Plastic waste breaks down into smaller and smaller pieces over time and is finding its way into the atmosphere, in the furthest reaches of the planet and infiltrated most ecosystems on Earth and the most intimate parts of the human body. Dumping plastics, large volumes of which end up in the ocean, is not just ecologically disastrous, but it has also become publicly unacceptable.
The toxic effects of micro- and nanoplastics are determined by their characteristics, and the source of production i.e., synthetic or natural sources. The physical and chemical compositions of microplastics majorly determine their ecotoxicological risks. The consequence of the environmental accumulation of micro and nanoplastics exposed to biota pose risk for bioaccumulation and biomagnification at the trophic level and causes multiple ecological repercussions. Microplastics have already contaminated our entire planet. Eventually they become so fine that wind can carry them. Consequently, microplastics have been found in freshly fallen Antarctic snow, sea ice and surface water. They have found their way in the high-altitudes of Mount Everest and Himalayas. They have even been discovered at the deepest point of ocean.
There is a growing concern that the increasing presence of micro- and nanoplastics in aquatic habitats poses a threat to marine life. The insidious interactions between plants, soil, and micro- and nanoplastics in the agricultural environment could affect soil health, crop productivity, and threaten food safety and human health. Importantly, finer nanoplastics can be taken up by plants, induce oxidative stress and negatively affect plant growth. Nanoplastics will be just as ubiquitous as macro- and micro-plastics, but far more destructive to living organisms due to their ability to infiltrate cells.
RAINING DOWN ON US
The discovery of atmospheric micro(nano)plastic transport and ocean–atmosphere exchange points to a highly complex marine plastic cycle, with negative implications for human and ecosystem health. Discovering microplastics in the lowest layer of the atmosphere — where clouds form — is further evidence of the ubiquitousness of microplastics. Airborne microplastics are detected in cloud water in both the free troposphere and atmospheric boundary layer. The free troposphere is an important pathway for the long-range transport of air pollutants owing to strong wind speeds; it has been observed that airborne microplastics are also transported in the free troposphere and contribute to global pollution. The accumulation of microplastics in the atmosphere, especially at the poles, could also significantly alter the ecological balance of the planet and lead to severe loss of biodiversity. Airborne microplastics are degraded much faster in the upper atmosphere than on the ground due to strong ultraviolet radiation, and this degradation releases greenhouse gases and contributes to global warming. Plastics are hydrophobic but due to the prolonged exposure to ultraviolet light become hydrophilic.
Their presence in clouds is especially concerning, because some of the microplastics had molecular structures that could help to seed clouds, spurring them to produce ice or water. The particles could also contribute to cloud formation, which would affect their cooling impact on the Earth. This implies that microplastics account for the effects in future global warming projections and may have become an essential component of clouds, contaminating nearly everything we eat and drink via ‘plastic rainfall’. If this plastic air pollution is not addressed proactively, climate change and ecological risks may become a reality, causing irreversible and serious environmental damage in the future.
SO… WHAT ABOUT…?
Micro- and nanoplastics are emerging pollutants from many primary and secondary sources, pervasive and exist in every environmental compartment, already present across air, soil and sediment, freshwaters, seas and oceans, plants and thousands of species including humans, and in several components of the human diet. But like climate change and hazardous chemicals, most plastics are invisible to the naked human eye, meaning their impact goes relatively unseen. But these tiny plastic particles can travel worldwide, ending up in urban, rural, and remote areas. They take an even faster transport pathway than oceanic currents: the atmosphere. Moving through the air, micro- and nanoplastics can cover thousands of kilometers in a matter of days to weeks, creating what could be a never-ending loop of plastic transport. The serious potential for long-range transport means that micro- and nanoplastics can affect locations and populations vast distances from the sources of plastic pollution, making microplastics one of the most ubiquitous pollutants released by anthropogenic activities and a grave public health issue. The very characteristics of microplastics reveal their potential to be a dangerously potent vector for toxics and pathogens. Micro- and nanoplastics have major toxic effects on animal’s cell viability, oxidative stress, decreased immune response, inflammation, cytotoxicity, DNA damage, disruption of metabolism, neurotoxicity, impaired reproductive activity, and tumors in animals and human cells.
Based on existing evidence, it is apparent that humans can be exposed to micro- and nanoplastics via ingestion, inhalation and dermal routes. Following exposure, micro- and nanoplastics can cross biological barriers, potentially inducing toxicity that triggers the aforementioned oxidative stress, inflammatory reactions, and metabolism disorders, particularly gastrointestinal and pulmonary infections with potential effects on the digestive, respiratory, circulatory, and immunological systems, as well as the nervous, embryonic, and placental systems. Maybe the omnipresence and threat of micro- and nanoplastics will trigger the need of major attention as we have just begun to face the repercussions.