There were fears that the small amount of mercury in CFLs could cause problems if the bulbs were broken. But mercury is also released when coal is burned to generate power, and CFLs use less electricity than standard bulbs.
Matthew Eckelman and colleagues at Yale University calculated what the net mercury emissions would be of replacing one standard 60-watt incandescent bulb with an energy-saving CFL in 130 countries.
They used country-specific data on the proportion of power generated from coal, the coal’s energy content, efficiency of mercury emission control technology and rates of CFL recycling and breakage.
Most countries would see a net decrease in mercury emissions, even with relatively low CFL recycling rates. The most important factor was the amount of coal in the electricity mix. The UK, with 34% coal, would reduce its mercury emissions by 6.3 milligrams for each 60W incandescent lamp replaced.
European lamp makers have committed to reducing bulb mercury levels from the current 5mg limit. This would further boost the emissions benefit of switching to CFLs.
EU governments have meanwhile agreed on a timetable for phasing out incandescent light bulbs and low-efficiency halogen bulbs.
The measures agreed by member state representatives in the Ecodesign Regulatory Committee will eventually require all light bulbs to have an efficiency rating of at least C under the EU’s A-G energy labelling system.
The restrictions, to be in place by 2012, will be introduced as "implementing measures" under the energy-using products Directive.
The measures will start to have an impact from next year.