Picano et al. BMC Cancer 2012, 12:157 http://www.biomedcentral.com/1471-2407/12/157 mechanism of cataract formation remains partially un- known. There is a transparent layer of cells covering the in- terior frontal side of the capsule that covers the lens. This layer maintains the function of the lens by slowly growing toward the center, achieved through cell division at the per- iphery. Because radiation is especially harmful to dividing cells, exposed cells at the equator are most prone to dam- age. For unknown reasons, damaged cells move toward the rear of the lens before converging on the center. Such cells prevent light from travelling straightforward resulting in opacity. Because of their location along the lens’ visual axis, relatively minor posterior subcapsular cataracts can have great impact on vision. The estimated eye dose is around 0.5 mGy/procedure, when no eye protection is used. Until recently, the dose threshold for radiation-induced lens opa- cities were considered 2 Gy for a single dose or 5 Gy for fractionated dose [94]. However, several epidemiological studies among Chernobyl clean-up workers, A-bomb survi- vors, astronauts, residents of contaminated buildings, and surveys of staff in interventional rooms indicate that there is an increased incidence of lens opacities at doses below 0.5 Gy and even suggest a stochastic hypothesis (non- threshold effect) [95]. Whether deterministic or stochastic in nature, cataracts can be found in up to 50% of interven- tional cardiologists [96]. The reasons for this high prevalence are threefold: first is that operator’s eyes are exposed to scattered x-rays. Without lead protection, the operator’s eyes receive a mean entrance skin dose of 165 μSv per coronary angi- ography session, but the use of lead eyeglasses reduces this level to 37 μSv [96]. Second (avoidable) is the fre- quent failure of some cardiologists to use protective leaded eyewear [68]; and probably third, that the allowed occupational dose limits were too high to even keep an alert in mind. On April 21, 2011, ICRP slashed the earl- ier dose limit of 150 mSv in a year for the lens of the eye to the present 20 mSv in a year, averaged over a defined period of 5 years, with no single year exceeding 50 mSv [9]. The unique model of interventional cardiologists and x- ray exposure: mind the brain! First-generation interventional cardiologists who entered the catheterization laboratory 20 to 30 years ago were inclined to believe that radiation is not such a serious mat- ter [21], and in particular that the brain is a radio-resistant organ, that the eye lens can tolerate high doses of radiation, that no significant mitotic activity is present in the adult brain, and that no biologically plausible effect can link x-ray exposure to non-cancer disease such as neurovascular and neurodegenerative disorders. Unfortunately, all these assumptions have been disproved in the last decades. As a consequence, operators in catheterization laboratories should modify the habit of not using personal protective Page 9 of 13 garments to shield their forehead and brain. The first line of whole-body defence against unwanted effects of radiation exposure is to start implementing the principles of justifica- tion and optimization in the catheterization lab. The second line of defence is to strictly adhere to protection practice (Figure 6). The use of a ceiling-suspended screen [21] or 0.5 mm lead cap attenuates scatter dose to the head by a factor of 2000 of baseline [96]. The radioprotection cabin reduces the head dose from over 100 μSv per procedure to the environmental background level of 1 μSv per procedure [18]. The third action is to start to look systematically to health (including brain) effects on the interventional cardi- ologist and staff population, which may become a Rosetta stone for decoding the long-term effects of radiation ex- posure, a recognized major environmental pollutant in the contemporary environment [97]. Contemporary invasive cardiologists and interventional radiologists are therefore a suitable research model for addressing many unanswered questions on the link between radiation exposure and proven but still imprecisely defined (eye cataract or brain cancer), probable (vascular) and possible (neuro-cognitive) serious health effects. In fact, two major studies on interventional cardiologists, invasive radiologists and catheterization laboratory staff are now at the starting blocks: the North American and the Italian studies (Table 3). The Multispecialty Occupational Health Group (MOHG) undertook a cohort mortality study comparing cancer and other serious disease outcomes (including car- diovascular disease and cataracts) in 44,000 physicians per- forming fluoroscopically guided procedures (including interventional cardiologists, radiologists, neuroradiologists and others) and in 12,000 non-interventional radiologists with risks in 101,000 physicians who are unlikely to be exposed to occupational radiation (e.g., family physicians or psychiatrists) [98]. Member organizations of the MSOHG include the Society of Cardiac Angiography and Intervention, Society of Interventional Radiology, Heart Rhythm Society, American College of Radiology, American College of Cardiology, Society of Neurointervention Surgery, American Association of Physicists in Medicine, and Society of Invasive Cardiac Professionals. The MSOHG is collaborating with experts in occupational health, epidemiology, and radiation effects who are from the United States Navy and the Radiation Epidemiology Branch of the National Cancer Institute, to perform epi- demiological studies addressing the fundamental questions important to all those working in such an environment. In Italy, The Healthy Cath Lab study is organized by the Italian National Research Council with endorsement of the Italian Society of Invasive Cardiologists, and is designed by interventional cardiologists for interventional cardiologists. The Italian study population will consist of 500 exposed (high, medium, and low exposure) interven- tional cardiologists and staff (technicians and staff) and