The Office of Environmental Health Hazard Assessment debated whether fluoride belongs on the Proposition 65 list.
California voters passed Proposition 65 in 1986. It requires that businesses and products post warnings if people are being exposed to cancer-causing substances.
While municipalities would have been exempt from telling people the fluoride in tap water could cause cancer, toothpaste makers would have had to add a Prop. 65 warning label on the box or tube.
Dentists were worried because it could scare people into not brushing their teeth.
"We want to reduce the amount of tooth decay, and we've done a fantastic job in reducing tooth decay, such that half the children now in the United States don't have any tooth decay at all," UCSF Dental Professor Howard Pollick said.
But scientists urged the panel not to dismiss the studies, especially the results in children.
"Exposure to fluoride in tap water during the mid-childhood growth spurt ages 5 to 10 is linked to higher levels of osteosarcoma in males age 10-19," Environmental Working Group senior scientist Rebecca Sutton said.
In the end, the panel unanimously voted against warning labels on toothpaste because the studies overall were inconclusive.
Public health officials praised the move.
"The science is very clear and very definitive. This is a safe and effective tool to prevent dental decay and it in no way has any ill effects on any individual's health," American Association of Public Health Dentistry spokesperson Catherine Hayes said.
More than 800 chemicals are on the state's Prop. 65 carcinogen list. Fluoride will not be added.