Researchers highlight growing global concern over microplastics, urging swift international cooperation to prevent irreversible harm to both ecosystems and human health.
Review: Twenty years of microplastics pollution research—what have we learned? Image Credit: Maksim Safaniuk / Shutterstock
In a recent review article published in the journal Science, researchers summarized the current understanding of microplastics' origins and sources, their effects on the environment and human health, and the urgent need for global solutions to microplastic pollution.
They concluded that while public concern and international efforts to address microplastic pollution are growing, significant scientific uncertainties remain, particularly in evaluating long-term impacts and the effectiveness of proposed interventions.
More data is required not only to assess these impacts but also to prevent unintended consequences that may arise from hasty measures.
Sources of microplastics
Experts define microplastics as particles of solid plastic less than 5mm in size. They are made of materials like nylon, polyester, and acrylic and have been present in the environment since at least the 1960s, with their abundance increasing rapidly over time.
They have accumulated along coastlines, in the water column, deep into the ocean, and in sea ice. Microplastics have been detected near the summit of Mount Everest, the highest mountain in the world.
They have been found in the invertebrates that form the foundations of food webs and in apex predators. Their capacity to spread across ecosystems globally, unhindered by political boundaries, underscores the scope of the problem.
Common contributors of microplastics to the environment include fibers from textiles, paints, tire abrasion, and personal care products. The role of plastic-coated fertilizers, nets, and rope from fisheries has been increasing.
Human activities are at the root of microplastic release into the environment, and the largest source appears to be the fragmentation of large plastic items in natural systems.
These items are often durable while in use, but their resistance to degrading causes them to accumulate and persist for long periods. Microplastics can also travel long distances from the point where they enter the environment through rivers and waste streams.
Environmental effects
Once in the environment, microplastics are consumed by detritivores, deposit feeders, and filter feeders. In addition to invertebrates, they can also be eaten by fish and birds and transfer rapidly along food chains.
Researchers have found evidence of microplastics in more than 1300 species, including insects, birds, mammals, and fish. Their effects begin at the subcellular level but may threaten the stability of entire ecosystems. However, much of this research has been conducted under controlled laboratory conditions, and translating these findings to real-world ecosystems remains challenging.
Plastics can disrupt endocrine systems and lead to gastrointestinal blockages and other internal damage. Depending on the quantity and kind of microplastics consumed, different organisms show different effects, including signs of reduced survival, stunted growth, and altered reproduction.
There is a growing consensus that more real-world data is needed to confirm these effects on a larger scale and across diverse species.
Microplastics and human health
Humans are exposed to microplastics through drinking water, air, and food; they have been found in tea, sugar, honey, table salt, and seafood. This can happen due to contamination in natural environments or during the packaging and processing of foods.
Perhaps as a consequence of these exposures, microplastics are increasingly found in human bodily fluids, organs, and tissues, including the placenta, blood, kidney, and liver. They may move from one part of the body to another but can also be removed through exhalation, urine, and feces.
People who smoke have higher microplastic concentrations in their lungs than non-smokers. While early research indicates potential health risks, especially concerning respiratory and endocrine functions, more comprehensive studies are needed to clarify the full extent of these risks.
Responses to microplastic pollution
While plastics have been very successful and are indisputably useful to humans, societal concerns regarding their dangers are increasing. Surveys suggest that people are more concerned about plastic pollution in oceans than they are about climate change.
People are also increasingly concerned that microplastics may cause cancer or other health conditions. Yet, despite rising public anxiety, policymakers and stakeholders face significant challenges due to gaps in data on the actual risks posed by microplastics.
With much still unknown about the risks that microplastics may pose, it is difficult for policymakers and other stakeholders to form a consensus and make decisions. Regulatory frameworks are being explored, including those that mandate testing, disclosure, and monitoring of plastic levels in water for drinking.
The focus is also shifting from ‘downstream’ approaches at the point where microplastics enter the environment to ‘upstream’ approaches that address manufacturing processes. Researchers stress the need for swift and coordinated global action, as microplastics transcend national borders and affect ecosystems worldwide. Delays in policy implementation could lead to further environmental damage that may be irreversible.
Researchers suggest following the ‘precautionary principle’ and focusing on preventing harm when there is reason to believe there is a danger, even if further data is needed.
Another aspect of this is involving the public in consultations and keeping them informed about recognizing and avoiding hazards.
International cooperation is essential to ensure that the measures taken to reduce microplastic pollution do not cause new problems or shift the burden of pollution from one region to another.
Conclusions
The risks associated with human exposure to microplastics have been challenging to measure, and environmental effects are still not fully known.
Researchers hope to gain greater clarity on these impacts within the next decade. However, it is increasingly clear that waiting for perfect evidence before taking action could result in irreparable harm.
Political boundaries do not constrain microplastics and are pervasive globally, pointing to the need for international cooperation.
Researchers recommend that policy action be swift and not delayed until further assessment and data are available. They recommend adopting the precautionary principle.
Journal reference:
- Twenty years of microplastics pollution research—what have we learned? Thompson, R.C., Courtene-Jones, W., Boucher, J., Pahl, S., Raubenheimer, K., Koelmans, A.A. Science (2024). DOI: 10.1126/science.adl2746, https://www.science.org/doi/10.1126/science.adl2746