Microplastics and Co-Contaminants in Rural Iowa Streams

Plastics have revolutionized consumer goods, making things cheaper, quicker, and easier to obtain. From packaging to toys to kitchenware, plastics are now ubiquitous in modern society. However, this convenience comes with a cost.

Scientists have documented increasing evidence of the severity of plastics pollution. These range from ingestion of microplastic particles (<5mm in size) by aquatic and terrestrial organisms (including humans) to being a transport mechanism for pathogens and other environmental contaminants. To date, most of the research has been on microplastics in marine environments. Little research has been conducted on microplastics transport and co-contaminant issues in terrestrial environments such as rural American farmland streams. This study was the first microplastics study of rural streams specifically to be conducted in Iowa and the nation.

To better understand these issues, a team of researchers from the United States Geological Survey (USGS) and the University of Iowa conducted the first statewide assessment of microplastics in rural Iowa streams. They also investigated potential relations between microplastics to other contaminants that are known to be present in Iowa streams. Assessment of these small-first-order streams revealed potential relationships between microplastics and representative land uses, laying a foundation for more informed management practices and helping us to understand microplastic dynamics on agricultural lands that support the diets—and thus indirect exposure potential—for millions of people.

ISTC research chemists John Scott and Lee Green analyzed for microplastics in the samples collected for this study. They investigated wastewater treatment plant outputs such as effluent and residual solids (biosolids), amended/unamended soil samples, and surface waters near the test sites to identify the major sources of environmental microplastics, how these materials move in the environment, and their final fate.

Measurements for other contaminants by project partners is currently underway. While the evaluation of microplastic results is still in progress, preliminary findings show that agricultural sites have very high concentrations of microplastics, and stream bed sediments appear to be a major sink for this class of contaminants.

Funding from this research came from the Center for Health Effects of Environmental Contamination (CHEEC) at the University of Iowa and in-kind contribution from the USGS. Final results are expected in summer 2023.