Many bamboo or other 'eco' toothbrushes are not actually 100% compostable, as their bristles are made of nylon. These are the only truly compostable toothbrushes out there. 100% Biodegradable They can be commercially composted, which means you can put them in your compost bin rather then in the waste bin. Soft bristles are derived from castor oil, handle is PLA.