Listed as a high hazard (9 on a 10-point scale) by the Environmental Working Group, fluoride shows evidence of organ toxicity, neurotoxicity and carcinogenic activity. The Food and Drug Administration considers fluoride an "unapproved new drug," and the Environmental Protection Agency lists it as a "contaminant," yet it is found in the majority of toothpastes.
A natural substance made by bees to seal the hive, propolis has antibacterial, antifungal and anti-inflammatory properties. It is used for tooth and gum health in a number of natural toothpastes.
Used as a whitening agent in toothpaste and mouthwash, peroxide has a strong bleaching action. It is banned by the Japanese government in all cosmetics except hair dyes, and shows some evidence of neurotoxicity and organ toxicity.
A synthetic disinfectant and antimicrobial agent, triclosan is listed as an antimicrobial pesticide by the EPA. It is used in toothpaste to prevent gingivitis. Triclosan shows evidence of liver toxicity, and also ends up as a pollutant in rivers and lakes, where it is very toxic to aquatic life, according to the Environmental Working Group.
Found in nature as sand or quartz, silica is the most abundant mineral in the earth's crust. It is used in toothpaste as an abrasive cleaning agent. Though dangerous to respiratory health in aerosol form, silica is safe in toothpastes, according to the EWG.
A naturally occurring sweetener usually derived from birch trees, xylitol also shows a preventive effect in reducing cavities and tooth decay.