A chemical that has been linked to cancer cell growth is being used by millions of Americans in toothpaste every day, it has emerged, according to a report of Daily Mail Online.
The company behind Colgate Total insists that triclosan, which it uses to stave off gum disease, is safe to use because the toothpaste was approved in 1997 by the Food and Drug Administration.
But the toxicology documents used by the FDA to approve the toothpaste were only released early this year after a Freedom of Information Act lawsuit last year - and reveal the agency relied upon company-backed science to reach its conclusion, Bloomberg News reported.
The 35-page report reveals the FDA had concerns that triclosan could increase the risk of cancer - but Colgate said the chemical was only problematic in large doses.
But evidence available at the time, as well as newer studies, show there are indeed concerns with the chemical - including premature births and underdeveloped bones in animals, the Daily Mail Online reports.
'The recently released pages, taken alongside new research on triclosan, raise questions about whether the agency did appropriate due diligence in approving Total 17 years ago,' scientists told Bloomberg.
In 2010, a student linked triclosan, which has commonly been used to reduce bacteria contamination, to reduced fertility in mice and a 2013 study linked it to lowered sperm production in rats.
And a study from 2003 found triclosan in the urine of 75 per cent of 2,517 Americans - including children - who were tested by the Centers for Disease Control and Prevention.
Despite evidence - including pages in the report showing how tests found fetal bone malformations in mice and rats - Colgate deemed the results irrelevant because they were conducted on animals.
'We have created a system where we are testing these chemicals out on the human population,' scientist Thomas Zoeller told Bloomberg. 'I love the idea they are all safe. But when we have studies on animals that suggest otherwise, I think we're taking a huge risk.'
Still, Colgate said that the 35 pages do not prove the chemical is harmful to humans and said that its safety is proved by more than 80 clinical studies of 19,000 people.
'In the nearly 18 years that Colgate Total has been on the market in the U.S., there has been no signal of a safety issue from adverse-event reports,' spokesman Thomas DiPiazza told Bloomberg.
He added that, while the FDA had been worried about the chemical's carcinogenicity, a study in 1997 found it did not pose a cancer risk for humans.
Colgate said it has no plans to reformulate Total toothpaste.The FDA said on its website that triclosan is 'not known' to be dangerous to humans - but the results found in animals has given them enough of a reason to run tests again.
Drug regulators are now reviewing the dangers of the chemical, but they will only re-visit the approval of Total if they find a great enough reason to.
In a sign of the concern over the chemical, Minnesota lawmakers banned the chemical in May. Avon and Johnson & Johnson have also announced plans to cut the chemical from its products.
In 2010, the European Union banned triclosan in materials that come into contact with food.