Effetti biologici da esposizione occupazionale a campi magnetostatici utilizzati in imaging a risonanza magnetica nucleare: una rassegna

IntroductionMagnetic resonance imaging is an established diagnostic tool involving the exposure to static magnetic fields (SMF) of patients and health personnel (technical radiographers, radiologists, anaesthetists, surgeons, maintenance staff). The occupational exposure to SMF will be ruled within the framework of the Directive 2004/40/EC of European Union covering health and safety requirements regarding the exposure of workers to the risks arising from electromagnetic radiations, which must be incorporated into domestic law by each member state by 30 April 2008. It applies to all employment sectors and addresses workers’ short-term adverse health effects, excluding possible long-term effects. This study aims at critically review the recent literature on the topic to analyse the requirement of delivering information and training of workers and of providing appropriate health surveillance Materials and methodsTo identify the studies published after the review by the World Health Organization (WHO) in the series Environmental Health Criteria, a search was carried out on Medline. The strategy defined for searching studies was based on the following MeSH terms, which comprehensively addressed the problem: (i) Magnetic Resonance Imaging, (ii) Electromagnetic Fields, (iii) Electromagnetic Fields/adverse effects, (iv) Occupational Health. These terms were used to build appropriate search strings to identify the studies according to the following criteria: (i) English language, (ii) inclusion of review, case-control and cohort study, controlled trials, (iii) abstract availability (iv) human effects, mechanism of action, pathophysiology or in vitro studies, (v) studies published after 2004/01/01 not considered in the WHO review. 28 studies were available in full-text.ResultsAlthough studies carried out at cellular level are valuable to investigate mechanisms of interaction, they do not evidence any specific effect as a consequence of the exposure to SMF. Experimental studies carried out on volunteers show that short-term exposure to SMF induces a variety of acute effects: (i) vertigo, nausea, metallic taste in the mouth occur during body or head movement within SMF in T range and may result in a possible negative influence on the performance of workers during critical procedures, (ii) changes in blood pressure and heart rate within the range of the physiological variability occur for exposure to SMF up to 8 T, (iii) induction of ectopic heart beats and increased likelihood of re-entrant arrhythmia (possibly leading to ventricular fibrillation) may occur in susceptible workers), (iv) a decrease of working memory and of eye hand coordination are dose dependent for exposure to 1.5-3 T SMF and may affect the performance of workers executing delicate procedures. The limitations of the available studies, however, do not allow drawing firm conclusions about the effects of SMF on the described endpoints. ConclusionAccording to the Directive 2004/40/EC the employer shall ensure that workers exposed to risks from electromagnetic fields receive any necessary information about the potential risks and that appropriate health surveillance shall be carried out to prevent any adverse health effect. According to the reported data it will not be unchallenging to deliver information and training and to provide appropriate health surveillance to the exposed workers. In fact, information and training activities might be influenced by the uncertainties resulting from the available evidence, requiring the ability of balance between few certainties and several doubts, while the same uncertainties might reflect themselves on the preventive and periodical examinations aiming at preventing short term adverse health effects.