There is actually a very small percentage about 3% - of mercury in zinc air batteries. Mercury is a stabilizing element in hearing aid batteries. There has been legislation to remove mercury from hearing aid batteries. So the battery industry came together and decided that by 2011, as an industry, there will no longer be mercury in hearing aid batteries. In many state across the United States, mercury laws have already been implemented.
Multiple hearing aid battery manufacturers are currently selling mercury free hearing aid batteries in the United States.
For more information on mercury battery laws, check with your local government.
For further information on what is the best hearing aid battery type to use with your hearing aids, discuss this with your hearing professional.