Domestic and mineralogical waste, as well as the one produced from various industries is thrown mostly in rivers, generating high amounts of heavy metals, becoming a threat for the health for residents in the areas near the river. Established techniques of polluted water can be used in order to determine the heavy metal concentration, however, some of them require high energy consumption and sophisticated equipment. An alternative method is an indirect analysis that consists in the measurement of cadmium levels with the application of the optical study of the flora of the region near the river using UV-VIS basic spectroscopy. This analysis allow us to measure the amount of cadmium (a metal that directly affects health) found in the grown plant. Therefore, the specie Raphanus sativus was used due to its fast growth, and the fact that it requires high amounts of water for its growth. The optical study was performed applying different concentrations of the metal. Such concentrations were kept within then maximum of heavy metals allowed in river water. UV-VIS spectroscopy was performed with light sources of unpolarized light and polarized light, allowing performing the purposed research, determining a trend line between the concentration of cadmium and the intensity of light around 675nm of the spectrum.