[German scientists advise] that the bulbs should not be left on for extended periods, particularly near someone’s head, as they emit poisonous materials when switched on.
Peter Braun, who carried out the tests at the Berlin's Alab Laboratory, said: "For such carcinogenic substances it is important they are kept as far away as possible from the human environment."
Several carcinogenic chemicals and toxins are released when the environmentally-friendly compact fluorescent lamps (CFLs) are switched on, including phenol, naphthalene and styrene.
Andreas Kirchner, of the Federation of German Engineers, said: "Electrical smog develops around these lamps."
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