They are a byproduct of tobacco smoke. They are added to rubber during vulcanization, and they are used in color photography. They are called amines because the chemicals in this broad class are derived from ammonia. They are therefore distinguished by having both nitrogen and carbon in their molecules. Aromatic amines have already been identified as mammary carcinogens in laboratory rats.
Human data is scarcer, but the authors point to some compelling occupational data.
Women workers in a Russian dye-making factory, for example, showed excess rates of breast cancer. In carrying out their study, the authors had to first establish an analytical method for measuring the presence of monocyclic aromatic amines in biological fluids. Indeed, they are the first team of researchers to detect such contaminants in human milk. As the authors themselves note, the implications of such a finding are gravely important. Aromatic amines such as o-toluidine, on the other hand, are known to cause ductal carcinomas in rats.