**1. Introduction**

Aside from the multiple industrial applications of aluminum, it has applications in different fields including a few uses related to human consumption such as a flocculant in drinking water purification processes, as an adjuvant in vaccine preparation, and as an additive in beverages, foods (e.g., sweets and cheeses), antiperspirants and deodorants, among others [1–7]. However, the soluble forms of aluminum are considered potentially toxic because of their high water solubility and genotoxic capacity and because of our exposure to these soluble forms at subacute and chronic levels on a daily basis [6,8,9]. Recent estimates from the United States denote that middle-class young adults consume an average of 105–150 mg of aluminum per day in food and drinks, indicating that individuals are constantly exposed to the frequent use or consumption of different forms of aluminum [4,5,10]. Genomic instability is an essential prerequisite for the generation of multiple carcinogenesis-related alterations and mutations [11,12]. Therefore, trace (essential) elements, metals, and heavy metals are associated with breast cancer [13–16] either because cancer decreases the levels of some trace metals or because the metals cause or are associated with the genesis of cancer [2,17]. One of these trace metals is arsenic, which is associated with genomic instability, lung cancer [18], and deficient manganese metabolism, causing mitotic deregulation associated with genomic instability in humans [19]. Iron, another trace metal, is also associated with the development of genomic instability and liver, lung, and intestinal cancers in experimental rats [20]. Moreover, copper has reportedly been linked to genomic instability, which is related to breast cancer in rats [21], whereas cadmium is related to breast cancer in women worldwide [22]. Furthermore, aluminum chloride is being investigated for its potential relationship with neurological, hepatic, bone, and hematological conditions as well as with breast cancer [23–27]. Therefore, we assessed the genotoxic effects of aluminum concentration in Sprague Dawley rats and determined whether a link could be established with N-nitroso-N-methylurea (NMU)-induced breast cancer. This will aid in the development of new strategies for addressing exposure due to the use and/or consumption of soluble forms of aluminum as well as in the elucidation of their genotoxic hazards and relationship with the genesis of breast cancer in humans.

#### **2. Materials and Methods**
