Microplastics and nanoplastics have emerged as one of the most pervasive environmental contaminants of our time. Found in oceans, freshwater, Arctic ice, mountain air, human blood, and even brain tissue, these tiny polymer fragments present a growing but incompletely understood threat to ecosystems and human health. Landmark studies published in 2024, 2025, and 2026 have linked micro- and nanoplastics (MNPs) in human tissue to significantly elevated cardiovascular risk, immune modulation, reproductive harm, and the infiltration of brain tumors. Illinois waterways, including the La Moine River system that flows through Macomb and western Illinois, are documented conduits of microplastic contamination— connecting local pollution to a continental-scale problem.
The term microplastics refers to plastic particles smaller than 5 millimeters in their longest dimension, roughly the size of a sesame seed or smaller. Nanoplastics, a subset of even greater concern, are particles smaller than 1 micrometer (one-thousandth of a millimeter), small enough to enter the bloodstream and cross cellular membranes. Together, they are designated as micro- and nanoplastics, or MNPs. Scientific awareness of microplastics began to accelerate in the early 2000s, with Richard Thompson’s landmark 2004 publication in Science, coining the term and documenting plastic fragments in marine sediments dating back decades. Since then, researchers have detected MNPs in virtually every environmental compartment on Earth, including oceans, the atmosphere, and drinking water, as well as in human blood, lungs, liver, kidneys, placenta, and brain tissue.
The sheer ubiquity of MNPs, combined with a rapidly expanding body of evidence linking them to adverse health outcomes in humans and wildlife, position microplastic contamination as one of the most significant and least fully understood environmental and public health challenges of our era. Understanding the science, tracking the pathways, assessing the risks, and formulating effective responses are urgent imperatives.
Microplastics are not a single substance but instead, a heterogeneous family of synthetic polymers. The most commonly detected types in environmental and biological samples include Polyethylene (plastic bags, bottles); Polypropylene (food containers, caps, textiles); Polystyrene (packing, disposal cups); Polyethylene terephthalate (bottles, clothing); Nylon (fishing nets, carpet, clothing); and Polyvinyl chloride (pipes, medical tubing, flooring).
There are two major categories of microplastics. The first is primary microplastics which are intentionally manufactured in small sizes. They include microbeads used in personal care products (facial scrubs, toothpastes), industrial abrasive pellets, and pre-production resin pellets called “nurdles” that serve as raw material for plastic manufacturing. Despite the 2015 Microbead-Free Waters Act in the United States, primary microplastics continue to enter waterways from legacy products (small plastics used in cosmetics and bio medical products) and industrial spillage. The other category is secondary microplastics which form through the degradation of larger plastic items via ultraviolet (UV) photodegradation, mechanical weathering (wave action, abrasion), thermal breakdown, and biological activity. For example, A discarded plastic bottle on a riverbank will fragment over the years into progressively smaller pieces, eventually producing particles in the microand nano plastic range. Secondary sources are by far the dominant category of environmental MNP contamination.
Several intrinsic properties of plastic polymers make microplastics uniquely problematic. First, they have extreme durability. Most synthetic polymers resist natural biodegradation for hundreds to thousands of years, meaning MNPs persist and accumulate in the environment indefinitely on a human timescale. In addition, there is the water-repelling nature of most plastic surfaces, which causes them to preferentially adsorb hydrophobic persistent organic pollutants (POPs) from surrounding water-- including DDT, PCBs (polychlorinated biphenyl), PAHs (polycyclic aromatic hydrocarbon), and dioxins. Therefore, MNPs act as vectors for chemical contamination. Further complicating the problem, plastics contain a complex mixture of additives (plasticizers, flame retardants, UV stabilizers, pigments, and antimicrobials) that can leach into tissues and the environment upon ingestion or degradation.
Global plastic production exceeded 400 million metric tons in 2022 and continues to grow. Without significant intervention, cumulative plastic waste in the environment is projected to triple by 2060. Every ton of plastic produced is a future source of microplastic contamination.
Microplastics enter freshwater and terrestrial environments through multiple pathways. One way is through wastewater treatment plant (WWTP) effluent. Conventional treatment removes 90–99% of incoming MNPs, but even a 1% passthrough translates to billions of particles discharged daily from a single large facility. Fibers from synthetic clothing and microbeads from personal care products are dominant WWTP inputs. A single load of synthetic clothing can release over 700,000 microfibers, which travel through municipal sewer systems to WWTPs and beyond. Also, road tire abrasion generates an estimated 6 million tons of tire wear particles globally each year, making it one of the largest single sources of microplastic pollution. These particles are transported via stormwater runoff. Plastic mulch landscaping fabric, irrigation tubing, silage wraps, seed coatings, polymer- coated fertilizers all degrade in soil, releasing MNPs into agricultural landscapes. Rainfall washes accumulated plastic debris, tire fragments, and atmospheric deposition from impervious surfaces into storm drains and receiving waters. Though microbeads have been partially banned, legacy products and non-regulated formulations continue to contribute to primary MNPs. Airborne microplastics, primarily fibers and fragments, settle onto land and water surfaces far from their point of origin, demonstrating long-range atmospheric transport.
Rivers serve as the primary conduits transporting landbased microplastic pollution to lakes and oceans. Urban rivers concentrate MNPs from point sources (WWTP outfalls, industrial discharges) and diffuse sources (stormwater, atmospheric fallout). The concentration of microplastics typically increases downstream, especially below WWTP discharge points. A study by McCormick and colleagues at Loyola University Chicago, published in Ecosphere (2016), measured microplastic concentrations in the surface waters of nine rivers in Illinois. Their findings were striking. Across nine Illinois rivers, mean microplastic flux was 1,338,757 pieces per day. Concentrations were significantly higher downstream of WWTP effluent outfalls in seven of the nine rivers studied. The dominant microplastic types were pellets, fibers, and fragments, identified as polypropylene, polyethylene, and polystyrene. (McCormick, A. R. et al. (2016;. Ecosphere, 7(11), e01556).
Once in aquatic systems, MNPs follow several pathways. Denser particles and biologically encased MNPs sink and accumulate in river and lake sediment, creating long-term reservoirs of contamination. Aquatic organisms, from zooplankton to fish, ingest MNPs either directly or by consuming contaminated prey. Filter feeders such as mussels are particularly vulnerable. MNPs and their adsorbed chemicals can bio magnify through food chains, with higher concentrations observed at upper trophic levels, ultimately reaching human food sources. MNPs can become re-aerosolized from water and soil surfaces, enabling transport between environmental compartments and to remote locations.
Humans are exposed to MNPs through three primary pathways: ingestion, inhalation, and dermal contact.
A comprehensive review published in Nature Medicine in September 2025 by Lamoree and colleagues at the Vrije Universiteit Amsterdam, synthesized the growing evidence on MNP health impacts. The review established that experimental models demonstrate MNPs can cross cellular barriers in the lungs and intestines. They can also enter systemic blood circulation; and accumulate in reproductive organs, the placenta, liver, and kidneys, and penetrate the blood-brain barrier, accumulating in brain tissue .
While the accumulating evidence is concerning, establishing definitive causation—as opposed to correlation—between MNP exposure and specific diseases remains a significant scientific challenge. Confounding variables, limitations in MNP quantification methods, small sample sizes, and the ubiquity of exposure make controlled human studies extremely difficult. The field is rapidly evolving, and current findings should be interpreted as strong signals warranting precautionary action and intensified research rather than as established causal proof.
Part 2 will look at possible threats to Illinois in general and McDonough County specifically.
