The widespread presence of synthetic pollutants, such as Per- and polyfluoroalkyl substances (PFAS) and microplastics, often leads to confusion about their nature. While both are pervasive and persistent, they are fundamentally distinct categories of contaminants. They are defined by unique chemical compositions and physical forms. Understanding the separation between these two pollutants is necessary to grasp how they move through the environment, where they originate, and how they affect biological systems.
Defining PFAS and Microplastics
Per- and polyfluoroalkyl substances, or PFAS, are a large class of synthetic chemicals manufactured and used globally since the 1950s. They are defined by a chain of linked carbon and fluorine atoms, forming a bond extremely resistant to natural degradation.
This stability is why they are commonly referred to as “forever chemicals,” persisting in the environment and accumulating in biological systems. Examples like PFOA and PFOS are widely known due to their historical use in products such as nonstick coatings, stain-resistant fabrics, and firefighting foams.
Microplastics, in contrast, are a physical category of pollution defined by size: any plastic fragment less than five millimeters in length. They are composed of polymer materials, such as polyethylene terephthalate (PET) or polyvinyl chloride (PVC), which are the building blocks of larger plastic items.
These particles are categorized into two main types based on their origin. Primary microplastics are manufactured to be small, such as microbeads in cosmetics. Secondary microplastics form from the breakdown of larger plastic debris due to environmental weathering. Their chemical compositions and shapes can vary extensively depending on the source material.
The Key Differences in Composition and Form
The most fundamental distinction is that PFAS is a chemical class, while microplastics are a physical one. PFAS are individual molecules defined by their structure, often existing as invisible chemicals dissolved in water or incorporated into materials. They are designed to repel water and oil, and their small molecular size allows them to be highly mobile, traveling long distances through groundwater and air.
Microplastics, conversely, are solid particles composed of large polymer chains, meaning they are a physical entity defined by their millimeter-scale dimensions. Their behavior in water is governed by physical properties, such as density, causing them to either float or sink to the sediment. While microplastics are polymers, they may contain or be treated with PFAS compounds, such as polytetrafluoroethylene (PTFE).
Why They Are Often Found Together
Despite their differences, PFAS and microplastics share many common environmental pathways and are frequently detected in the same locations. Both pollutants are introduced into the environment through wastewater treatment plants, industrial discharge, and the breakdown of consumer goods. For instance, synthetic textiles treated with PFAS for water repellency can shed microplastic fibers coated with the chemical during washing, leading to a co-release into water systems.
The physical interaction between the two contaminants, known as adsorption or sorption, is also a major reason for their co-occurrence. Microplastic particles possess a large surface area that attracts and collects environmental contaminants, including highly mobile PFAS chemicals. This means the microplastic effectively acts as a carrier, concentrating the PFAS on its surface, which alters the movement and distribution of the chemical in the ecosystem.
How Each Contaminant Causes Harm
PFAS and microplastics pose different biological threats due to their distinct mechanisms of action. Harm from PFAS is primarily chemical, stemming from the compounds’ ability to be absorbed and bioaccumulate in the tissues of living organisms. Once inside the body, PFAS can interfere with natural processes due to their structural similarity to certain organic molecules, leading to metabolic and endocrine disruption. Studies have linked exposure to specific PFAS to altered cholesterol levels, reduced immune system response to vaccines, and an increased risk of certain cancers.
The harm from microplastics is fundamentally physical, where ingestion causes mechanical damage or obstruction in the digestive systems of wildlife. In organisms, the particles can cause false satiation, leading to reduced food intake and malnutrition. A secondary source of harm comes from chemicals that leach out of the microplastic particles, such as plasticizers or the PFAS chemicals that have adsorbed to the surface. This means the particle causes physical distress while also serving as a vector for chemical exposure.