Microplastics are tiny plastic particles less than 5 millimeters across. Some are manufactured at that size, like the beads in cosmetics. Most come from larger plastics that break down. A plastic bottle left in the sun eventually fragments into countless pieces too small to see. These particles now contaminate oceans, rivers, soil, and air.

They are everywhere. Scientists have found microplastics in Arctic ice, deep-sea sediments, drinking water, and human blood. They enter the food chain when fish and shellfish eat them. The health effects on humans are still being studied. Some plastics carry toxic chemicals. Others absorb pollutants from the environment and concentrate them.

Reducing microplastics is hard. They are a byproduct of the plastic economy. Better waste management helps. Filters on washing machines catch synthetic fibers. Bans on microbeads in cosmetics have taken effect in many countries. But the sheer volume of plastic in use means particles will keep shedding for decades. The problem is persistent, like the material itself.

Common sources

• Synthetic clothing fibers
• Tire wear particles
• Cosmetic microbeads
• Plastic packaging breakdown
• Industrial pellets