A rigorous analysis of results obtained from the recent high-level theoretical calculations and experimental measurements on nucleic acid fragments, especially nucleic acid bases and base pairs are reported. It is well-known that environmental factors such as metal cations and water molecules are essential for the proper physiological structure of nucleic acids. Variation in degree of hydration or metal cation concentration can change the structure (conformation) of deoxyribonucleic acid (DNA). Nucleic acid bases are endowed with high photostability and such property is attained due to the ultrashort excited state lifetimes, which is in the order of subpicosecond. The extremely small excited state lifetime, which is a consequence of the ultrafast nonradiative deactivation, does not allow enough time for photoreaction. The high-level theoretical calculations show that electronic singlet excited state geometries of nucleic acid bases are generally nonplanar. The excited state geometrical distortion along certain bonds leads to conical intersections between the excited and ground state potential energy surfaces, and thus facilitate the ultrafast nonradiative deactivation. There is one more environmental factor that due to the fast development of a new type of technology – nanotechnology – becomes vital for the society and its well-being. It has been speculated that airborne nanoparticles may cause allergic reactions or lead to asbestosis type of disease upon prolonged exposure. Several investigations have suggested that fullerene derivatives can induce nucleotide chain cleavage mainly at the guanine site of DNA. Nanomaterials can bind to DNA, protein, and different receptor sites, and thus can travel to those sites, which might be usually unaccessible. Therefore, a rigorous toxicological analysis of nanomaterials will be needed before widespread commerical application.