On Jan. 27, 2012, Wisconsin SB 407 (2011) was introduced to the purpose of prohibiting the sale of zinc air button cell batteries. On April 02, it was signed into a law by governor Walker.
According to SB 407, "no person may sell at retail or offer for sale at retail a zinc air button cell battery that is manufactured after January 1, 2013, unless the manufacturer has certified to the department that the zinc air button cell battery contains no mercury that was intentionally introduced."
And this Bill is supported by leading battery manufacturer in the USA.
Zinc air button cell batteries has high energy densities and are relatively inexpensive to produce, which can be used for hearing aids.