Le mercure dans les ampoules à basse consommation

5. Do environmental benefits of compact fluorescent lamps outweigh potential risks?

The SCHER opinion states:

3.4 Question D
Weigh the risks identified in A), B) and C) against the reduction of mercury emissions from coal-based power plants due to the lower electricity consumption of CFLs compared to conventional household lamps. Incorporate and consider the potential health risks from mercury when CFLs are broken, accidentally in the household or after disposal, into the life cycle analysis of CFLs, taking into account the reduction of human health and environment risks resulting from the potential reduction in mercury emissions from coal-based power plants and the reduction of the emission of other pollutants due to the lower electricity consumption of CFLs compared to conventional household lamps.

In A, B, C, the SCHER concluded that the environmental risks of Hg due to the use of CFLs are very low. The VITO (2009) report demonstrated that the amount of Hg emitted over a CFL lifetime per lumen is approximately 10% lower than that of conventional CLS bulbs (Table 2). Considering that this normalized life cycle estimation (per lumen per hour) includes both the Hg emissions from the use and disposal phase, the net emission reduction would be in that order of magnitude, if all conventional household lamps were replaced by CLFs. It is noted that halogen lamps emit even less Hg (up to 39% less) per lumen per hour.

The SCHER would like to point out, that weighing risks to different targets (human health and ecosystems) from different outputs (Hg and greenhouse gases) from different products (various kinds of light bulbs) presents some considerable challenges that are only just now being addressed in risk assessment. Hence, SCHER is only able to give a partial and somewhat tentative response to this question.

That said, from an environmental perspective, the weighing of the adverse effects of mercury emissions on ecosystems and the climate effects of greenhouse gas emissions is made easier by virtue of the mercury emissions per lumen per hour being roughly similar across lamp types (see Table 2). On the other hand the environmental impacts of the CFLi lamps is considerably less than the rest, Thus the VITO (2009) report presents data per lumen per hour for each environmental indicator including two main environmental impact indicators, i.e. total energy consumption (GER) and total global warming potential (GWP). These indicators for CFLi lamps are about 25% of those of GLS-C and GLS-F lamps. Compared to HL-MV- LW, HL-MV-HW and HL-LV lamps, CFLis have 13%, 53% and 22% less impact on the GER indicator and 13, 47 and 25% less impact on the GWP indicator, respectively.

The SCHER is therefore of the opinion that CFLis offer a net environmental benefit as compared with the other light bulbs considered. This could have been more equivocal had the Hg released from disposal caused the life cycle emissions from the CFLis to exceed that of the other light bulbs. And it is more equivocal in weighing the environmental gains from CFLis with any risks to human lives from accidental exposures. Often, weighing different effects across different targets is based on expert judgements. Another approach is to weigh different effects on the basis of public values and with a common monetary measure. Thus, the variations per lumen per hour across light bulb types would be modulated as follows: for greenhouse gases with the social cost of carbon; for human health with values for life and/or healthy life years; for ecosystems with the values of ecosystem services. That would put all the risks in the same monetary units.

SCHER counsels some caution with this kind of approach but is of the opinion that for the sake of developing transparent assessment that properly informs management and policy the above-described approach to risk-benefit analysis needs to be given more critical attention. For example, without this kind of approach, it would not be possible at this stage for SCHER to give an opinion that weighs the benefits from greenhouse gas reductions with any increased risks of accidental exposure for human health. That has to remain a matter for judgement in the risk management process.

Source & ©: SCHER,  Opinion on Mercury in Certain Energy-saving Light Bulbs (2010), p.15.