Thesis: Living organisms can be exposed to chronic irradiation, which can have harmful consequences on exposed populations and impact subsequent generations. The study of multi- and transgenerational consequences of chronic exposure to an environmental pollutant is a growing area of interest for the protection of humans and the environment. The aim of this thesis was to better understand the effects of chronic exposure to ionizing radiation over four generations, using as model organism the nematode Caenorhabditis elegans. For this purpose, a systems biology approach was adopted, which included transcriptomic profile, miRNAs and transcription factors analysis, coupled with phenotypic and apical endpoints. The results highlight an impact of ionizing radiation on reproduction, sperm quality and quantity, as well as germ line progression, with an intensification of the effects between the first and the second generation. The epigenetic involvement in the stress response induced by ionizing radiation was also showed, which indicated that these changes can be transmitted up to three generations after irradiation has stopped. In addition, results from the present study were compiled in a conceptual "Adverse Outcome Pathway" where increased DNA damage and oxidative stress represent key events leading to toxic effects on the germ line and gametes ultimately resulting in reprotoxic effects at the individual level