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Disentangling the influence of microplastics and their chemical additives on a model detritivore system
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Researchers disentangled the physical and chemical effects of microplastics on freshwater detritivores, finding that chemical additives leaching from plastics contributed more to negative impacts on organisms than the polymer particles themselves.
Microplastics (MPs) can negatively impact freshwater organisms via physical effects of the polymer itself and/or exposure to chemicals added to plastic during production to achieve desired characteristics. Effects on organisms may result from direct exposure to plastic particles and/or chemical additives or effects may manifest as indirect effects through ecological interactions between organisms (e.g., reduced food availability that impairs a consumer). To disentangle these issues, we used a simplified freshwater food web interaction comprising microbes and macroinvertebrate detritivores to evaluate the toxicity of 1) polyvinyl chloride (PVC) MPs without added chemicals (virgin), 2) the common chemical additive dibutyl phthalate (DBP), and 3) PVC MPs with incorporated DBP. Exposure to virgin PVC MPs (0.33 and 3.3 mg/L) caused negligible ecological effect with the exception of reduced macroinvertebrate feeding rates at 3.3 mg/L. Exposure to DBP (1 mg/L) both individually and when incorporated into the PVC MPs negatively impacted all tested endpoints, including microbial and macroinvertebrate respiration, feeding rate and assimilation efficiency. DBP leached rapidly from the MPs into the water, and also accumulated in macroinvertebrates and their food, providing multiple routes of exposure. Our findings suggest that additives which are intentionally incorporated into MPs could play a key role in MP toxicity and contribute to the disruption of key ecological interactions underpinning ecosystem processes, such as leaf litter decomposition.
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Aquatic toxicity of chemically defined microplastics can be explained by functional additives
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Researchers manufactured microplastics from four polymer types with precisely defined chemical compositions, including different additive formulations, and tested their toxicity to aquatic organisms. They found that the toxic effects of microplastics could largely be explained by the functional additives they contained rather than the base polymer itself. The study suggests that the chemical additives in plastics, not just the plastic material, are a primary driver of microplastic toxicity in aquatic environments.
Effects of Different Microplastics on Nematodes in the Soil Environment: Tracking the Extractable Additives Using an Ecotoxicological Approach
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Researchers examined how different types of microplastics affect soil nematode populations by tracking extractable chemical additives released from the plastic particles. They found that microplastic composition, size, and shape influenced the types and amounts of chemicals leached into the soil, which in turn affected nematode survival and behavior. The study highlights that the indirect chemical effects of microplastics may be just as important as their physical presence in determining soil ecosystem impacts.
Extractable additives in microplastics: A hidden threat to soil fauna
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Researchers compared the toxic effects of five types of microplastics and their extractable chemical additives on a common soil worm species. They found that the additives leaching from the plastics were the primary driver of toxicity, reducing worm growth and survival and disrupting gut microbiota. The study indicates that the chemical additives embedded in microplastics may pose a greater threat to soil organisms than the plastic particles themselves.
The contribution of additives to microplastic aquatic toxicity – A testing approach with model additives on selected aquatic organisms
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Researchers developed a systematic testing approach to distinguish between the physical effects of microplastic particles and the chemical effects of their additives on aquatic organisms. The study found that polyethylene microplastics alone showed no significant toxicity to water fleas or protozoa, but the inorganic additive zinc oxide was toxic on its own. The findings suggest that the additives embedded in plastics, rather than the plastic particles themselves, may be the primary drivers of toxicity in some cases.
Evaluating microplastic particles as vectors of exposure for plastic additive chemicals using a food web model
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Researchers used a bioaccumulation model to estimate how much chemical exposure humans and wildlife receive specifically from ingesting microplastic particles — versus other environmental routes — and found that microplastics only become a meaningful source of chemical additives when ingestion rates are high and the plastic contains substantial concentrations of hydrophobic chemicals. The work helps clarify when microplastics are a significant chemical vector, finding that health risks from this pathway are likely negligible at currently estimated ingestion rates.
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