25
Feb
Interactions Between Microplastics and Pesticides Exacerbate Their Environmental Health Threat, Studies Find
(Beyond Pesticides, February 25, 2025) A literature review of over 90 scientific articles in Agriculture documents microplastics’ (MPs) increase in the bioavailability, persistence, and toxicity of pesticides used in agriculture. The interactions between MPs and pesticides enhance the threat of pesticide exposure to nontarget organisms, perpetuates the cycle of toxic chemical use, and decreases soil health that is vital for productivity.
“The increasing presence of MPs in agricultural ecosystems has raised concerns about their impact on pesticide bioavailability, efficacy, and environmental behavior,†says study author Kuok Ho Daniel Tang, PhD., a global professor in the Department of Environmental Science at the University of Arizona. He continues, “These synthetic particles interact with pesticides through adsorption and desorption processes, altering their distribution, persistence, toxicity, and uptake by plants and other organisms.â€
Microplastics in the Environment
As Beyond Pesticides has previously reported, microplastics are ubiquitous and threaten not only human health but all wildlife in both aquatic and terrestrial ecosystems. The universal distribution of plastics means that they cannot be avoided. Humans and other organisms take up plastics in the form of microparticles and nanoparticles by inhalation, ingestion, and skin contact every day. Microplastics are about the width of a human hair; nanoplastics are much smaller, about twice the width of a DNA strand. Larger pieces of plastic are ground down to these tiny sizes by weathering, temperature, biological processes, and chemical conditions. (See additional Daily News coverage on microplastics here, here, here, and here.)
In agriculture, the primary sources of microplastics are plastic mulching, coatings on pesticides, and fertilizers such as biosolids, in addition to the particles carried to the fields by wind and water. As Dr. Tang says: “MPs are defined as plastic fragments measuring less than 5 mm in size and can either result from the breakdown of larger plastic waste (secondary MPs) or be produced intentionally for specific uses (primary MPs), like in cosmetics, pharmaceuticals, and industrial applications. Owing to their diminutive size, durability, and widespread presence, MPs have been recognized as a global pollutant that can interact with various environmental contaminants, including pesticides.â€
Recent research on interactions with antibiotics shows that MPs can act as a vehicle, “extending their presence in the environment and aiding in the development and spread of antibiotic-resistance genes,†Dr. Tang states. (See studies here and here.) He continues, saying that these results have led to “growing concern that the co-occurrence of MPs and pesticides may exacerbate the environmental risks associated with these contaminants through complex physicochemical interactions.â€
The interaction between MPs and pesticides depends on various factors, such as the physical and chemical properties of both the MPs and pesticides involved, as well as the environmental conditions they are subjected to, including pH, temperature, salinity, and organic matter content. The pervasiveness of a pesticide in the environment after contact with MPs can be altered based on their modes of action, including systemic pesticides that are absorbed by plants and transported throughout their tissues and contact pesticides that kill pests with direct contact.
Adsorption and Bioavailability
Bioavailability of pesticides represents “the extent to which a pesticide is accessible to organisms or biological systems, such as plants, microbes, or animals, for absorption, uptake, or interaction,†Dr. Tang shares. “It determines how effectively a pesticide can exert its intended effects, such as killing pests or controlling weeds, and it also influences the pesticide’s potential for environmental contamination and toxicity,†he continues. Through the interaction with MPs, the bioavailability of pesticides can be altered by the mechanism of adsorption, where particles from the pesticides can adhere to the plastic’s surface.
Relevant studies find:
- “Aged microplastics have higher surface areas for adsorption, thus reducing pesticide bioavailability. This decreases the effectiveness of systematic and contact pesticides.â€
- MPs cause atrazine to dissipate in soil, preventing it from reaching targeted plants.
- “Higher pesticide adsorption also increases the persistence of pesticides, as indicated by their extended degradation half-lives.â€
- “MPs exhibited strong adsorption for all three compounds (azoxystrobin, picoxystrobin, and pyraclostrobin)†and modified residual behaviors.
- [T]he extent of pyraclostrobin’s adsorption to MPs greatly affected its presence in black bean seedlings.†(See studies here and here.)
- Interactions with MPs show a “marked increase in the adsorption of the highly hydrophobic fungicides azoxystrobin and tebuconazole in the soil.â€
- “MPs, particularly tire fragments, may reduce the bioavailability of chlorpyrifos.†(See study here.)
- “Germination rates of crops such as lettuce significantly declined in the presence of MPs combined with neonicotinoid insecticides. This trend was more pronounced with aged MPs, likely due to their enhanced ability to adsorb pesticides.â€
When microplastics influence the uptake of pesticides, they can cause a decline in pesticide effectiveness that results in lower agricultural yields and higher costs of having to apply more pesticides. This creates a reliance on toxic chemical usage that threatens health and the environment and increases costs for farmers, given reduced pesticide product efficacy. This review helps to highlight the significant negative effect of microplastics on pesticide bioavailability that “prompt the application of more pesticides to achieve the desired level of crop protection, which bears cost and environmental consequences,†Dr. Tang comments.
Pesticide Persistence
Persistence of chemicals, including pesticides, refers to the duration they stay active in the environment within the soil, in water and air, or on vegetation before decomposing. “Usually, persistence is measured through the half-life (T½), which signifies the time required for half of the pesticide to decompose,†the study explains. MPs can alter the half-life of chemicals, as is referenced in scientific literature.
Study results include:
- “MPs could greatly extend the degradation half-lives of atrazine, azoxystrobin, epoxiconazole, metolachlor, myclobutanil, simazine, tebuconazole, and terbuthylazine in aquatic environments… For instance, the half-life of terbuthylazine was notably increased from 31.8 days to 45.2 days when exposed to a concentration of 10 g/L of MPs.â€
- “In degradation experiments, MPs substantially prolonged the persistence of herbicides in aquatic environments, from 86.6–231 days in the control to 346.5–886.2 days in water.â€
- “The introduction of MPs led to a reduction in the residues of 3,5-dichloroaniline in the soil and its availability for biological uptake, consequently resulting in an increased persistence of 3,5-dichloroaniline within the soil environment.†(See studies here and here.)
- “Certain findings indicate that MPs can greatly impede the breakdown of pesticides in aquatic environments, resulting in increased persistence of these chemicals in water.†(See studies here and here.)
- “MPs inhibited chlorpyrifos degradation, extending its half-life and reducing its breakdown rate. This prolongs the pesticide’s active period and raises concerns about soil contamination and off-target effects.â€
- By MPs reducing the bioavailability of fungicides, “this extended their persistence in the soil and diminished the absorption of these chemicals by maize plants.â€
Soil Health
Crop production and food security rely on healthy soils, which can be adversely impacted by pesticides. (See previous coverage here.) The scientific literature contains research showing that the interactions between MPs and pesticides can exacerbate these environmental impacts.
This includes:
- Adverse impacts on soil structure and cohesion. (See here and here.)
- Effects on the ability of soil to retain water. (See here.)
- Affected presence of soil nutrients, such as organic matter, and microorganisms. (See here, here, here, here, here, and here.)
- Decreased microbial activity in the soil. (See here and here.)
Pesticide Toxicity
While the majority of current literature focuses on lower bioavailability of pesticides as the most prominent adverse impact of organism interaction with MPs, there are studies that find an increase in toxicity of pesticides that come into contact with organisms.
Studies report:
- “[T]oxicity observed in the MPs after herbicide adsorption being markedly greater than in those without herbicides.â€
- “[A]ged MPs demonstrated increased toxicity when paired with neonicotinoids… This enhancement in toxicity is attributed to the ability of aged MPs to absorb higher amounts of neonicotinoids, thus increasing their harmful effects.â€
- Nontarget organisms, many of which provide beneficial ecosystem services, are negatively impacted by MPs. Earthworms, which enhance soil health in ways that leads to better crop productivity, have reduced enzyme activity and oxidative harm as a result of combined exposure to MPs and imidacloprid. This exposure “reduced their weight gain and antioxidant enzyme activity, potentially impairing their ecological role in agriculture.†(See study here.)
- Also in earthworms, exposure to “MPs and carbendazim led to a significant drop in biomass, indicating a potential interaction effect. Furthermore, simultaneous exposure triggered synergistic reactions, ranging from oxidative stress to alterations in critical organs like the body wall, intestines, and reproductive systems. A comparison of various indicators showed that the seminal vesicles and ovarian follicles were the most affected during the combined exposure.†(See study here.)
- The presence of MPs “not only heightened chlorpyrifos accumulation in radishes but also diminished the fresh root biomass of the plants.â€
A Path Forward
Organic agriculture negates microplastic–pesticide interactions that influence pesticide performance, soil health, and environmental safety. In adopting organic methods for land management, it provides a holistic solution that focuses on soil health while also protecting the health of all organisms. Organic agriculture embodies an ecological approach to farming that does not rely on or permit toxic pesticides, chemical fertilizers, genetically modified organisms, antibiotics, sewage sludge, or irradiation. The National Organic Standards Board (NOSB) works to continuously improve upon these standards and acts as a lifeline from the government to the organic community as it considers input from the public regarding organic integrity. In this context, Beyond Pesticides has commented to the NOSB that it should phase out the use of plastic in its certification production systems and in the packaging of organic food.
Visit Keeping Organic Strong to learn more about the 2025 NOSB meeting, as well as our 2024 comments that include plastics in organics as a research priority. Reference our previous action regarding plastics in farming, water, and food, and stay informed on other opportunities to engage by signing up to receive our Action of the Week and Weekly News Update emails.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Tang, K. (2025) Effects of Microplastics on Bioavailability, Persistence and Toxicity of Plant Pesticides: An Agricultural Perspective, Agriculture. Available at: https://www.mdpi.com/2077-0472/15/4/356.
