The last module of the subject will be dedicated to the study of the toxicology of several groups of pollutants of environmental relevance. Three examples of heavy metals (lead, mercury and cadmium), a metalloid (arsenic), the main groups of pesticides (insecticides, herbicides, fungicides and rodenticides) and the main organochlorine contaminants (pesticides, PCBs, dioxins and benzofurans) will be studied. Organochlorine pesticides have been included in the group of organochlorine pollutants instead of pesticides because the strong restrictions applied to them in all European Union countries and other developed countries make the use of these compounds as pesticides practically null. . However, the high environmental persistence of these compounds, as well as the massive use that is still made of them in developing countries means that they cannot be considered as highly relevant environmental pollutants. The list of compounds could be broader. and include other compounds (more heavy metals, animal or vegetable biotoxins, etc.). However, given the temporary limitations, only those mentioned above have been included.