warm, humid summers and cool, damp winters. Northern Iran, as well as most portions of Iran, is separated by mountains. As a result, the air in Teheran is very dry. When driving to Ramsar from Teheran, one drives up the mountains until arriving at a tunnel. On passing through this tunnel and coming out the other side, the environment is very different; it is more humid and green due to moisture from the Caspian sea, and this abundance of mist and rain is part of the attraction for tourists from the desert zones of Iran. Radioactivity Ramsar's Talesh Mahalleh district is the most radioactive inhabited area known on Earth, due to nearby hot springs and building materials originating from them. A combined population of 2,000 residents from this district and other high radiation neighborhoods receive an average radiation dose of 10 mSv per year, ten times more than the ICRP-recommended limit for exposure to the public from artificial sources. Record levels were found in a house where the effective radiation dose due to external radiation was 131 mSv/a, and the committed dose from radon was 72 mSv/a. This unique case is over 80 times higher than the world average background radiation. The prevailing model of radiation-induced cancer posits that the risk rises linearly with dose at a rate of 5% per Sv. If this linear no-threshold model is correct, it should be possible to observe an increased incidence of cancer in Ramsar through careful long-term studies currently underway. Early anecdotal evidence from local doctors and preliminary cytogenetic studies suggested that there may be no such harmful effect, and possibly even a radio-adaptive effect. More recent epidemiological data show a slightly reduced lung cancer rate and non-significantly elevated morbidity, but the small size of the population (only 1800 inhabitants in the high-background areas) will require a longer monitoring period to draw definitive conclusions. Furthermore, there are questions regarding possible non-cancer effects of the radiation background. An Iranian study has shown that people in the area have a significantly higher expression of CD69 gene and also a higher incidence of stable and unstable chromosomal aberrations. Chromosomal aberrations have been found in other studies. Radiation hormesis was observed in a study that also recommended that Ramsar does provide justification to relax existing regulatory dose limits. Pending further study, the potential health risks had moved scientists in 2001–02 to call for relocation of the