Initial tests on isolated mammary cells derived from a normal human gland were later replicated in studies on mice, and the results were the same: long-term exposure to concentrations of aluminium caused cells to form tumours and metastasise.
“I think we should avoid all deodorants containing aluminium salts,” co-author André-Pascal Sappino told The Local.
“And it's very difficult to be sure that the so-called ‘without aluminium' brands really are without,” added the oncology professor from the University of Geneva.
Sappino said the team's earlier research was treated with scepticism, but mounting evidence meant it was much easier to get published this time.
For now, aluminium salts were a "suspect, not yet convicted", said the professor, who drew an analogy with asbestos, the use of which is banned in Switzerland and the European Union.
“Asbestos is cheap, has very attractive industrial potential, and it took 50 years to ban it. We hope it doesn't take so long to ban aluminium salts,” said Sappino.
Like asbestos, aluminium is not detectably mutagenic in bacteria, but subcutaneous injections of aluminium salts in mice resulted in “very aggressive tumours”.
While the study has not completely established a formal link with breast cancer, Sappino said he would advise all women against using deodorants that contain aluminium salts.
Men too should think twice: while breast cancer among men is rare, its incidence is rising, Sappino said.
The oncologist said he fully expected to face resistance from the cosmetics industry.
“Now the fight will begin. They will act like the tobacco industry and say that proof in human beings is lacking.”
Sappino said he expected that team's finding would make it easier to secure funding to further examine the cancer-causing effects of aluminium salts.
The study, co-authored by four researchers from the Clinique des Grangettes, is published in the International Journal of Cancer.