What are microplastics ?
A particle is officially considered a microplastic if it is any fragment of plastic measuring less than five millimeters about 5mm in length. Five millimeters is roughly the size of a standard sesame seed or a pencil eraser.
In short: Microplastics are tiny fragments of plastic that are five millimeters long or smaller.
Most microplastics found in the environment are far smaller than 5mM—some are so tiny they’re only visible under a high-powered microscope. When these particles get even smaller, they cross a critical threshold: the realm of nanoplastics.
Nanoplastics are any plastic particles smaller than 1micrometer, or often specifically defined as less than 0.1 micrometers.. Their size allows them to bypass many of the body’s natural defenses and filtration systems.
The Two Main Types of Microplastics
Not all microplastics are created equal. They are classified based on their origin, which is crucial for determining how to limit them.
Primary Microplastics
These are plastic fragments that were intentionally manufactured to be microscopic for use in specific products. They enter the environment directly from their source.
SourceDescription & ExamplesMicrobeadsTiny, spherical particles once common in exfoliants, facial scrubs, and some toothpastes. (Largely banned in North America, but historically a key source.)Industrial Pellets (Nurdles)The raw plastic resin feedstock used to make nearly all plastic products. Spills during transport release millions of these into coastal waters.MicrofibersFine threads released from synthetic fabrics (polyester, fleece, nylon) when they are washed, dried, or simply worn down. These are a primary source of indoor air and water contamination.
Secondary Microplastics
These make up the majority of global microplastic contamination. They are created when larger, macroscopic plastic items break down over time due to weathering, UV radiation from the sun, and mechanical abrasion.
Breakdown Examples: Plastic bottles, containers, bags, fishing nets, and packaging left in the environment gradually shatter into smaller and smaller pieces.
Tire Dust: Car tires—which contain various synthetic polymers—shed vast amounts of microplastics onto roads, which are then washed into waterways or aerosolized into the air.
