Manufacturers around the world have long used mercury in batteries to prevent the buildup of hydrogen gas, which can cause the battery to bulge and leak.
Button Cell Batteries:
Button cell batteries are miniature batteries in the shape of a coin or button that are used to provide power for small portable electronic devices. The four major technologies used for miniature batteries are: lithium, zinc air, alkaline, and silver oxide. Button cell batteries can contain 0-25 mg of mercury (and sometimes more). Lithium miniature batteries contain no intentionally-added mercury. However, small amounts of mercury are still added to most zinc air, alkaline and silver oxide miniature batteries in order to prevent the formation of internal gases that can cause leakage. Zinc air batteries are used mainly in hearing aids; silver oxide batteries are used in watches and cameras; and alkaline manganese batteries are used in digital thermometers, calculators, toys and a myriad of other products requiring a compact power source.
Mercuric Oxide Batteries:
In mercuric oxide batteries, mercury is used as an electrode rather than an additive to control gas buildup. These are rather specialty batteries and are often used in hospitals, military facilities and commercial applications.. Those can use more than 25 mg of mercury. The mercury accounts for up to 40% of the battery weight and cannot be reduced without reducing the energy output of the battery. Mercuric oxide button cells once were widely used in hearing aids but now are prohibited in most countries. Larger mercuric oxide batteries still are produced for military and medical equipment where a stable current and long service life is essential.
Separate collection systems for batteries are in place in many countries around the world.
However, there are still problems in collection, which can be resolved mainly through political support for mercury-free batteries.
Relevant legislation and NGO policy work on batteries:
Directive 2006/66/EC on batteries and accumulators and waste batteries and accumulators, in the EU, set maximum mercury limits for alkaline and button cell batteries, and prohibit the marketing of mercury oxide batteries, although there may still be significant quantities of the latter that transit the EU in trade flows.
2012 - Study on potential for reducing mercury pollution from batteries
After also our continuous pressure, the EC decided talso carry out a study on the batteries – and more specifically the potential phase out of button cell batteries containing mercury, as part of the revised EU mercury strategy.To that end the consultant BIOS who is carrying out the study on dental amalgam was asked to also look at the battery issue.
A draft report is expected to be published soon. A stakeholder meeting is also expected to take place in March 2012 - the draft report will be presented, stakeholders will give input, and after that the consultant will have to put together the final report.
In the US, federal legislation exists on the Management of batteries - In 1996, the U.S. Congress passed the Mercury-Containing and Rechargeable Battery Management Act (9 pp, 134K, about PDF) and many states passed legislation prohibiting incineration and landfilling of mercury-containing and lead-acid batteries
In terms of regulating mercury content in batteries some US states have passed relevant Bills. For more information visit