Microplastics and PFAS – Combined risk and greater environmental harm
The combined impact of so-called ‘forever chemicals’ is more harmful to the environment than single chemicals in isolation, a new study shows.
Researchers at the University of Birmingham investigated the environmental effects of microplastics and PFAS and showed that, combined, they can be very harmful to aquatic life.
Microplastics are tiny plastic particles that come from plastic bottles, packaging, and clothing fibres. PFAS (Per- and Polyfluoroalkyl Substances) are a group of chemicals used in everyday items like non-stick cookware, water-resistant clothing, firefighting foams, and numerous industrial products. PFAS and microplastic are known as "forever chemicals" because they don't break down easily and can build up in the environment, leading to potential risks for both wildlife and humans.
Both PFAS and microplastics can be transported through water systems on long distances, all the way to the Arctic. They are often released together from consumer products. Yet, their combined effects, and also the ways in which they interact with other polluting compounds in the environment, remain poorly understood.
To better understand the combined impact of these pollutants, researchers used Daphnia, commonly known as water fleas. These tiny creatures are often used to monitor pollution levels because they are highly sensitive to chemicals, making them ideal for determining safe chemical limits in the environment.
In this study, published in Environmental Pollution, the team compared two groups of water fleas: one that had never been exposed to chemicals and another that had experienced chemical pollution in the past. This unique approach was possible thanks to Daphnia's ability to remain dormant for long periods, allowing researchers to "resurrect" older populations with different pollution histories.
Both groups of Daphnia were exposed for their entire life cycle to a mixture of microplastics of irregular shapes - reflecting natural conditions- together with two PFAS chemicals at levels typically found in lakes.
The team showed that PFAS and microplastics together caused more severe toxic effects than each chemical alone. The most worrying result was developmental failures, observed together with delayed sexual maturity and stunted growth. When combined, the chemicals caused Daphnia to abort their eggs and to produce fewer offspring. These effects were more severe in Daphnia historically exposed to pollutants, making them less tolerant to the tested forever chemicals.
Importantly, the study found that the two chemicals lead to greater harm when combined – 59% additive and 41% synergistic interactions were observed across critical fitness traits, such as survival, reproduction and growth.
Lead researcher Professor Luisa Orsini emphasized the importance of the findings: “Understanding the chronic, long-term effects of chemical mixtures is crucial, especially when considering that previous exposures to other chemicals and environmental threats may weaken organisms' ability to tolerate novel chemical pollution.
“Our research paves the way for future studies on how PFAS chemicals affect gene function, providing crucial insights into their long-term biological impacts. These findings will be relevant not only to aquatic species but also to humans, highlighting the urgent need for regulatory frameworks that address the unintended combinations of pollutants in the environment. Regulating chemical mixtures is a critical challenge for protecting our water systems."
Dr Mohamed Abdallah, co-leading the research, said: “Current regulatory frameworks focus on testing the toxicity of individual chemicals, mostly using acute (short) exposure approaches. It is imperative that we investigate the combined impacts of pollutants on wildlife throughout their lifecycle to get better understanding of the risk posed by these pollutants under real-life conditions. This is crucial to drive conservation efforts and inform policy on facing the growing threat of emerging contaminants such as forever chemicals.”
Novel tools in chemical and biological screening with advances in artificial intelligence mean that we can understand the complex interactions among chemicals in the environment. Revising current methods for assessing environmental toxicity is therefore not only possible but imperative.”
Journal
Environmental Pollution
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Combined toxicity of perfluoroalkyl substances and microplastics on the sentinel species Daphnia magna: Implications for freshwater ecosystems
Article Publication Date
19-Oct-2024
Plastic mulch is contaminating agricultural fields
PNAS Nexus
image:
Plastic removal.
view moreCredit: Seeta Sistla
Using plastic sheets for weed control, even under current best management practices, pollutes soil with macro- and micro-plastics and negatively affect critical soil functions, according to a study. The United Nations considers soil plastic contamination an environmental health and food security threat. Around the world, over 25 million acres of farmland is seasonally covered with opaque plastic films used as “mulch” to prevent weeds, retain moisture, and warm soil—a practice known as “plasticulture.” Most studies have assessed plastic mulch soil contamination impacts using lab-based models or in experimental plots. Ekta Tiwari and Seeta Sistla sampled 12 farm fields on California’s Central Coast—a region of global agricultural importance. The authors surveyed fields after plastic mulch had been carefully removed for the season—a “best practice” to reduce plastic contamination in fields. However, all the fields surveyed had plastic contamination and the authors found up to 25 kg of macroplastic debris per hectare, covering up to 3.4% of field surface area. Microplastics were also found in all fields and microplastic concentrations positively correlated with macroplastic concentrations. Key soil heath traits were negatively correlated with macroplastic accumulation even at relatively low contamination levels, while no relationships with microplastic contamination were detected. Thus, current “best practices” are causing subtle but deleterious effects to soil. Because the use of plastic film mulches is rapidly expanding globally, the authors suggest exploring a non-plastic, biodegradable alternative to limit the threat to soil function and agricultural productivity caused by unabated plastic accumulation.
Strawberries planted into mulched beds 
Plastic contamination.
Plastic contamination from the field.
Credit
Seeta Sistla
PNAS Nexus
Article Title
Agricultural plastic pollution reduces soil function even under best management practices
Article Publication Date
22-Oct-2024
New study helps quantify climate change and ecotoxicity impacts of biodegradable microplastics
Over 20 million tons of plastic are estimated to end up in the environment every year, with much of it breaking down into microplastics that are harmful to the health of humans and wildlife. Biodegradable and bio-based plastics made from organic material are often touted as more sustainable alternatives, but until now, scientists haven’t had the tools to assess the impact of biodegradable plastics that are not disposed of properly.
A team of researchers from the Center for Industrial Ecology at the Yale School of Environment recently developed a valuable environmental impact assessment method to quantify the climate change and ecotoxicity impacts of biodegradable microplastics in the natural environment. The study, published in Nature Chemical Engineering, was led by postdoctoral associate Zhengyin Piao and co-authored by Yuan Yao, associate professor of industrial ecology and sustainable systems, and doctoral student Amma Asantewaa Agyei Boakye ’20 MEM.
Only 50% of bio-plastics are in fact biodegradable, and many biodegradable options are fossil-fuel based. Outside of the controlled conditions of a waste management facility, biodegradable plastics can have some of the same impacts as conventional plastics, including breaking down into small, problematic pieces. While they take less time to degrade, they also release greenhouse gases.
“There are a lot of people doing life cycle assessments for biodegradable plastics without being able to quantify impacts when those plastics enter nature,” said Yao. “There just hasn’t been any methodology available.”
For the study, the team modified existing tools to model the fate of biodegradable microplastics in aquatic environments, creating a more dynamic method that can account for fluctuations in emissions as plastics degrade. They tested it using the five types of biodegradable plastics that dominate the global market, two of which were made from petroleum and three from organic material.
Yao noted that it is a common assumption that growing biomass absorbs enough carbon dioxide to offset emissions from disposed bio-based biodegradable plastics. However, the research team found that the release of methane as these microplastics degraded in the natural environment had greater global warming potential than the carbon uptake from biomass growth.
The study also showed that the tradeoff depends on degradation rate and microplastic size. Shifting from conventional options to alternatives that degrade faster may reduce ecotoxicity, but itcould result in higher greenhouse gas emissions. The burden shifting did seem to disappear for smaller microplastics. For the smallest sizes tested — particles a million times smaller than an inch — the less biodegradable plastics had the highest emissions and toxicity.
“When plastic engineers try to design plastics, they often think higher biodegradability will definitely always be better,” Yao said. “Our results show that it’s not a linear relationship.”
The researchers said they hope the study will inform the design of sustainable plastics and waste management systems moving forward. The team is now refining the model to scale it up for a global analysis.
“Doing this kind of large-scale analysis is really important to have a better vision of what strategies the plastic industry can take if it wants to reduce all these environmental impacts,” Yao said.
Journal
Nature Chemical Engineering
Subject of Research
Not applicable
Article Title
Environmental impacts of biodegradable microplastics
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