Besides urging consumers to switch off unnecessary lights and reduce the use of spotlights, officials and green groups are calling for a switch to energy-saving bulbs. 'Regular bulbs have to be replaced every two months, energy-saving ones last up to two years,' says Green Sense project manager Gabrielle Ho Ka-po. Should we immediately refit all light fixtures with energy-saving bulbs? Henry Chung Shu-hung, associate dean of science and engineering at City University, says the new, energy-efficient lights have their drawbacks. Some types of low-energy bulbs don't last as long as they claim. And because the low-energy compact lights contain small amounts of mercury, a toxic heavy metal, disposing spent bulbs is an issue. That's why green groups are also calling on the government to set up a comprehensive recycling system when they promote the use of energy-saving light bulbs, says Hahn Chu of Friends of the Earth. In Britain, consumers are advised to seal bulbs in plastic bags for recycling.