In 2016, the US Food and Drug Administration (FDA) banned the antibacterial chemical triclosan from soaps, but it is still allowed in toothpaste. A new study out of the University of Massachusetts Amherst (UMA) shows that it – and several other chemicals – can build up in the bristles and soft parts of toothbrushes, and that certain toothbrushes were found to grab more triclosan than others.

The 2016 ban on triclosan from soaps, gels and wipes was enacted because the FDA said there was little evidence that products containing the chemical were any more effective in combating germs than simply washing with regular soap and water. There has also been concern about the chemical creating antibiotic-resistant bacteria, as well as worries about its toxicity and its effects as an endocrine-system disrupter.

Yet the chemical has also been found to be effective when used in toothpastes. According to The New York Times, toothpastes containing fluoride and triclosan cut plaque by 41 percent, reduced gum bleeding by 48 percent, and dialed back gum inflammation by 22 percent versus toothpastes without the antibacterial. Those benefits were deemed strong enough that the FDA decided to allow the chemical to remain in toothpastes, despite the warnings of some consumer advocacy groups.

In its work evaluating the build up of triclosan in toothbrushes, the UMA team developed a machine that simulated tooth brushing for two minutes twice a day for three months. Using human saliva, the researchers evaluated 22 best-selling toothbrushes and a range of both triclosan and non-triclosan toothpastes, which were applied to the brushes in a dose of three milligrams – about two-thirds the length of a standard brush head.

They found that the brushes held on to between seven to 12.5 full doses of triclosan, and that brushes that had rubbery tongue cleaners and polishing cups captured the most of the drug. They also found that the brushes captured significant amounts of other chemicals commonly found in toothpaste including methyl salicylate, anethole, and butylated hydroxytoluene (BHT), an antioxidant used in some whitening toothpastes that has raised eyebrows based on its role as a possible carcinogen in animal studies.

What's more, the team found that when a non-triclosan-containing toothpaste was applied to the brush, the accumulated triclosan was released in dose levels that are not regulated.

"We do recommend being aware of the uncontrolled accumulation and release behavior of this chemical, and potential unwanted exposure when users decide to switch to other regular toothpastes," said UMA environmental chemist Baoshan Xing. "We just want to make people aware that certain toothpaste chemicals can accumulate to substantial levels as they brush, and consumers can make up their own minds."

In addition to potential health concerns such a release of triclosan might have for individuals, the UMA team also points out that the findings could have environmental impacts as well.

"On a larger scale, our study also raises broad questions on the general design of consumer products with absorptive polymer components that are regularly exposed to chemicals during use, particularly those used in personal care products," said the authors of the study, which has been published in in the current issue of Environmental Science & Technology.

Source: University of Massachusetts Amherst