Keeping mercury in perspective
Use of mercury in compact fluorescent lamps (CFLs) has been very much in the news recently with, in my opinion, mixed effect. On the one hand the publicity has reinforced the need for all discharge lamps to be disposed of responsibly rather than being sent to landfill. This is particularly important in the domestic sector where people are probably less aware of such things, but it will also make commercial organisations think carefully about disposal.
On the other hand, the issue has been blown out of proportion by certain ill-informed media. Almost certainly, this will have put some people off changing from incandescent to fluorescent – again, mostly in the domestic sector but it could also have ramifications for businesses such as hotels. One can just imagine a paranoid guest refusing to stay in a room with CFLs.
As with all such issues, it’s important to be clear about the facts. The Environment Agency, which originally raised the issue in the UK, was trying to do just that. However, they were perhaps rather naïve in not anticipating the tabloid media’s exaggeration and embellishment.
Undoubtedly, the issue has arisen because of the increase of compact fluorescent light sources in the home. Whereas linear fluorescent lighting used to be confined to the kitchen and garage, the introduction of different types and shapes of CFLs has fuelled their use throughout the home and are helping many families contribute to reducing global warming.
I have no doubt that companies like our own have fuelled this increase and, I have to say, we’re rather proud of it. The fact of the matter is the switch to CFLs is making a really significant contribution to reducing carbon emissions through lower energy consumption.
Fluorescent lamps, and other gas discharge lamps, have always needed mercury to function, but the amounts of mercury have been greatly reduced in recent years. However, the mercury cannot yet be removed completely.
When the lamp is switched on, mercury vapour in argon or neon gas is excited and releases short wave ultra-violet light. This causes the phosphor powders on the glass to fluoresce and emit visible light.
Traditionally the mercury was inserted as a liquid and during the life of the lamp some of the mercury is absorbed into the glass, phosphors and electrodes. Because of this degradation and absorption, some lamps have had the amount of mercury increased to achieve a longer life.
However, a far more acceptable alternative is to use mercury amalgam rather than liquid mercury. Mercury amalgam is a 50% mercury alloy, used in lower doses than with liquid mercury, that is safe to touch in its solid form and has been used in dentistry, chemistry and mining for many years.
When the lamp is activated, the amalgam pellet vaporises to contribute to the process described above. When the power supply is switched off it returns to its safe solid form again, which has important implications for the safety of broken CFLs. As toxicologist David Ray, from the University of Nottingham, told the BBC: “If you smash one bulb then that is not too much of a hazard. However, if you broke five bulbs in a small unventilated room then you might be in short term danger.”
The amounts of mercury used in CFLs also need to be kept in perspective. Older style CFLs would typically contain 6-8mg of mercury; our amalgam lamps use less than 3mg. In comparison, a ‘button’ battery contains around 25mg, a mouth that has had an average number of amalgam fillings will contain as much as 500mg and a steam iron weighs in with a whopping 3500mg.
And, of course, the role that CFLs play in reducing electricity consumption helps to reduce other pollutants that enter the environment. In the case of coal-fired power stations, this results in a direct reduction of mercury pollution, as coal contains an average of 0.22mg/kg of mercury. This may not be a major consideration in the UK but in countries where coal is still widely used for power generation the figures are significant.
At the end of the day, this whole issue is about perspective and it’s important to get the message across that CFLs are safe and that they play a vital role in our moves to reduce climate change. As long as they are handled sensibly and disposed of responsibly any risk is negligible, and considerably less than with the mercury thermometers that people have been using for years without mishap.