http://www.futurity.org/arsenic-breast-cancer
The study, published in the journal EBioMedicine, presents results of breast cancer mortality data from a region in Chile where residents were inadvertently exposed to high levels of arsenic, which occurs naturally in many minerals.
Instead of an increase in mortality, as with many other cancer sites, the study found that breast cancer deaths were cut in half during the period that coincided with high arsenic exposure. The effect was more pronounced among women under age 60, with mortality in these women reduced by 70 percent.