“…Researchers seem to agree that BEN may result from prolonged exposure to one or more environmental toxicants acting alone or synergistically on genetically predisposed individuals/populations (Ganev and Petropoulos, 1999). Hypothesized environmental factors include exposure to: heavy metals (Wedeen, 1991), arsenic (Ganev and Petropoulos, 1999), dissolved nitrogen species (Radovanovic and Stefanovic, 1988), organic compounds leached from coal deposits (Feder et al, 1991), herbs containing aristolochic acid (Cosyns et al, 1994;Hranjec et al, 2005), mycotoxins (Dimitrov, 1960;Pfohl-Leszkowicz et al, 2002), and viruses (Kraus, 1996). Calcium, magnesium and selenium deficiencies in the diet have also been suggested, as this element is known to limit the damage from free radicals (Hoops and Feder, 1986;Maksimovic, 1987).…”