Claims the Daily Mail, based on a study conducted in Germany by breaking the bulbs and measuring the amounts of mercury released. The article makes it clear that such danger only arises when a bulb is broken, and that you can purchase protected bulbs which are very tough to place in certain rooms if you wish. Furthermore:
A spokesman for the Department for Environment, Food and Rural Affairs said: ‘Guidance from the Health Protection Agency makes it clear that the mercury contained in low energy bulbs does not pose a health risk to anyone immediately exposed, should one be broken.’
The Daily Mail still published the article anyway and opened with this paragraph:
Energy-saving light bulbs were at the centre of a fresh health scare last night after researchers claimed they can release potentially harmful amounts of mercury if broken.
Some more fine journalism from the Mail.