The only natural materials with the same properties as nylon are pig hair and badger hair. These tend to breed bacteria and raise ethical concerns, but they're probably not something we’d like to brush our teeth with anyways.

The Nylon-6 bristles are durable, anti-bacterial and BPA-free. What The Humble Co. has managed to do is replace 40% of the petroleum-based plastic with bioplastic made of the natural, plant-based ricin oil, hence using less petroleum than regular nylon bristles. Besides, ricin oil is obtained from the seeds of the castor bean plant which are inedible and constitute an agricultural waste.