Plastic resin pellets are classified as primary source microplastics, meaning that they were intentionally produced at the size ranging from 1–5 mm in diameter. Approximately 27 million tonnes of nurdles are manufactured annually in the United States. One kilogram of pelletized HDPE contains approximately 50,000 nurdles (approximately 20 mg per nurdle). They are typically under 5mm in diameter.

Environmental impact

Nurdles are a major contributor to marine debris. During a three-month study of Orange County beaches researchers found them to be the most common beach contaminant. Bathing beaches in East Lothian, Scotland have been shown to have covered with E. coli and Vibrio biofilms, according to a 2019 study.

Waterborne nurdles may either be a raw material of plastic production, or from larger chunks of plastics. A major concentration of plastic may be the Great Pacific garbage patch, a growing collection of marine debris known for its high concentrations of plastic litter.

Nurdles that escape from the plastic production process into waterways or oceans have become a significant source of ocean and beach plastic pollution. Plastic pellet pollution that has been monitored in studies is mainly found in the sediments and beach areas and is usually polyethylene or polypropylene, the two main plastic polymers found in microplastic pollution. Marine life is severely threatened by these small pieces of plastic; the creatures that make up the base of the marine food chain, such as krill, are prematurely dying by choking on nurdles.

Nurdles have frequently been found in the digestive tracts of various marine creatures, causing physiological damage by leaching plasticizers such as phthalates. Nurdles can carry two types of micropollutants in the marine environment: native plastic additives and hydrophobic pollutants absorbed from seawater. For example, concentrations of PCBs and DDE on nurdles collected from Japanese coastal waters were found to be up to 1 million times higher than the levels detected in surrounding seawater.

Plastic microbeads used in cosmetic exfoliating products are also found in water.