The chronic effects of radiation on humans may include shortening of life-span, increased incidence of leukemia and of solid tumors. X-irradiation causes DNA damage with blockage of the cell cycle at the G₂ stage and may lead to malignant transformation [1,2]. Cells assemble in the G₂ stage and enter mitosis together when the block­age is terminated. High dose radiation is required for an irreversible effect to occur. The effects of ionizing radia­tion include changes in chromosomal structure and chro­mosomal breakages. It is known that chromosomal break­age is the primary reason for the lethal effects of radiation on dividing cells [3-5].

      Carotenoids have been found to have anti-carcinogenic and anti-mutagenic effects in experimental systems [6,7]. β-Carotene is the most ubiquitous carotenoid in nature and is present in a variety of vegetables and fruits. It is a good antioxidant that binds to oxygen-free radicals and prevents reactions responsible for activation of pro-mutagenic sub­stances to electrophylic metabolites. β-Carotene may also stimulate inactivation of chemicals and prevent mutations by inducing mechanisms of detoxification [8,9].

      Porphyridium cruentum (PC) is a red microalga which belongs to the division Rhodophyta. During growth of PC in a liquid medium, the viscosity of the medium increases due to the release of polysaccharide from the cell surface [10]. Crude polysaccharide extract of PC contains a mix­ture of carotenoids and has been found to have anti viral, anti inflammatory, anti proliferative, chemo-preventive and chemo-therapeutic effects [11-13].

      In this study, we investigated the effects of βC and PC, separately or in combination, on Mitomycin C (Mit-C)- induced chromosome breakages in peripheral blood lymphocytes of radiology technicians who may be chroni­cally exposed to very low levels of radiation.