It could be lights out for Thomas Edison's light bulb.
Moves are being made around the world, including in Hong Kong, to ban incandescent bulbs on grounds they fail to meet today's standards of energy efficiency. Many see the old-fashioned light bulb giving way to the compact fluorescent lamp, or even the light-emitting diode (LED).
These would-be replacements come with some complicated shadows. Compact fluorescent lamps contain toxic substances - bad for the environment and possibly your health. And LEDs are expensive.
Compact fluorescent lamps undoubtedly save energy. They are as much as 80 per cent more efficient than incandescent bulbs. The fluorescents have become big sellers, their costs cut by mass production. At about HK$30 each, a compact fluorescent lamp will save enough energy to cover its purchase price in a year, according to environment officials.
That is part of the government's argument for a proposal released last month to outlaw the supply of incandescent light bulbs of 25 watts or above if they fail a minimum energy efficiency standard.
But each compact fluorescent bulb contains 2 to 5 milligrams of mercury. People should limit their exposure to 1 microgram, or a thousandth of a milligram, according to widely accepted recommendations, says Ron Hui Shu-yuen, chair professor of the department of electrical and electronic engineering at the University of Hong Kong.
'Energy saving is not equal to environmental protection. If the environment is to be truly protected, air, soil and water all have to be covered,' said Hui, an award-winning researcher in lighting science.
If the lamp does not break, the mercury might not present any danger. But when shattered, it could pose serious health risks, Hui said.
'If it breaks, the first thing to do is to run away from it and open all the windows to improve ventilation. Don't go near it for at least 15 minutes as the mercury will vaporise in higher temperature. The vaporised substance can easily find ways into your lungs and blood vessels and damage the central nervous system,' he said.
Hui said some officials refused to acknowledge the hazards by insisting the mercury level was too low to cause any impacts on health. But increasing scientific evidence suggests otherwise.
According to a recently published article in Environmental Engineering Science, a broken compact fluorescent lamp, or CFL, can continue to release mercury vapour for more than 10 weeks at a level that is a health concern for people. The research, conducted by Li Yadong and Li Jin, associate professors in the department of civil and environmental engineering at Jackson State University in Mississippi, is one of the original studies on the release of the toxic substance from a broken lamp. Eight compact lamps of four different wattages were tested. The mercury volumes contained in each of the sampled lamps ranged between 0.17mg and 3.6mg.
The scientists found that up to 86 per cent of the mercury could be released as vapour after the lamp was broken. In the worst case, it could take up to 128 days for all the mercury to escape fully into the air. The newer the lamp, the more mercury it could potentially release.
'The emission can last for weeks or even months,' the study said, 'and the total amount of mercury that can be released in vapour from new CFLs can often exceed 1mg. Since vapour mercury can be readily inhaled by people, rapid removal of broken CFLs and sufficient ventilation of rooms by fresh air are critical to prevent people from potential harm.'
Citing another study in 2008, the researchers say the release of 1mg of mercury vapour into a 500 cubic-metre room can expose a child to 10 times the recommended limit.
Hui said the potential hazards could be even bigger in Hong Kong, where most indoor environments were sealed, no effective system for collecting used lamps was in place, and warnings and education on the safe handling of the devices left much to be desired. These lamps easily break when people throw them out in their building or on the street. There are no measures in place at landfills to prevent the release of vapours and workers who collect rubbish are often unprotected from the hazards.
'I have told the government to start monitoring the blood of these workers who face a high risk of mercury poisoning, but apparently no one has listened,' Hui said.
At present, a chemical waste treatment plant in Tsing Yi is responsible for recycling the used lamps. It can handle about 400,000 fluorescent lamps a year. But that capacity fell far short of demand, Hui said. A spokesman for the Environmental Protection Department said the city currently had 900 collection points at residential estates and about 130 points in other places and it would continue to expand the network.
On its website, the department stresses that the amount of mercury in the lamps is small and unlikely to affect your health when they are broken. But the department does warn people not to vacuum pieces of a broken lamp and to use gloves to handle them. Pieces should be placed in sealable plastic bags for normal disposal.
Hui said the claim that fluorescent lamps were 80 per cent more efficient than traditional light bulbs needed to be placed in context. The amount of energy saved was tied to the lamps' longer lifespan - up to 8,000 hours, he said. But in fact, improper use of the lights will often lead to early expiration. Hui said heat generated by the lamp could shorten the life of its capacitor, especially if the lamp was installed with it glass tube pointed downward.
The energy that went into making each lamp, including mining the heavy metals and making the circuits, also had to be considered when thinking about the device's efficiency.
Despite the drawbacks, Hui says fluorescent lamps are a key transitional product for saving energy before other devices - cleaner and greener - became widely available and affordable. But better measures are needed to govern the production and recycling of the lamps.
While the government is consulting the public about phasing out the older light bulbs, it is at the same time offering sizeable funds through the Environment and Conservation Fund to charities to encourage people to switch to compact fluorescent light bulbs or LEDs.
One of the charities, the Tai Po Environmental Association, last year distributed more than 20,000 compact fluorescent light bulbs to residents. Dr Yau Wing-kwong, an appointed district councillor who runs the association, said it had taught people about properly disposing of the lamps. 'We believe there needs to be more publicity on responsible disposal,' he said.
Many countries are trying to phase them out because of their low energy efficiency
Metal filament wire that's heated until it emits light
Lifespan: 1,000 hours
Consume more power than the other bulbs ? and about 90 per cent of that energy produces heat, not light
Compact fluorescent (11-13W)
Billed as a green alternative to incandescent bulbs
Inner surface coated with phosphors that emit light
Tube filled with gas containing mercury vapour
Lifespan: 6,000 to 8,000 hours
80 per cent more efficient than incandescent bulbs, but each has 2 to 5 milligrams of mercury - could pose a serious health risk if it breaks, and disposal is a concern
Light-emitting diode (7W)
Produces less heat and lasts much longer than the other bulbs
Semiconductors create light when electrons hit holes and emit energy as photons
Cost: HK$90 to HK$100
Lifespan: 35,000 to 50,000 hours
80 per cent more efficient than incandescent bulbs and there?s no mercury, but LEDs can contain other toxic metals, including lead and arsenic
Sources: Electrical and Mechanical Services Dept, Optiled Lighting, US EPA, US FDA