From the company: We are the only 100% biodegradable toothbrush on the market! We utilize a proprietary process at our manufacturing facility to produce our Bamboo Toothbrush with 100% castor oil bristles, that contain zero plastics. We would be unable to legally claim the toothbrushes are 100% biodegradable, if the bristles were not made of 100% castor oil. This is a specific process that enables us to have the strength in the bristles to not have to add any additional binder ingredients and makes this toothbrush the only biodegradable toothbrush on the market. I'm not surprised there would be skepticism from other manufacturers about this process, which is why it is proprietary to our company.