The so-called "microbeads" turn up in face scrubs, acne treatments and toothpaste. The particles are too fine to be caught in wastewater treatment plants, and the plastic bits can pollute lakes and rivers.
A Colorado House bill to ban the microbeads by 2020 awaits a vote. The bill has the backing of large personal-care product manufacturers, including Johnson & Johnson.
Two other states have already banned microbeads. Dozens more states are considering joining Illinois and New Jersey.
The companies supporting the ban say they are already replacing plastic microbeads with biodegradable exfoliators.