Button batteries, toxicity

A common type of button battery, shown here, contains silver oxide or mercury(ll) oxide. Mercury is cheaper than silver, but discarded mercury batteries release toxic mercury metal into the environment. 

A five-year-old boy swallowed a button battery containing lithium (546). During the 4 days after ingestion, he developed a serum lithium concentration of 0.71 mmol/l without signs of lithium toxicity and with normal renal function. The battery was eventually retrieved by gastrotomy. 

Both cells are manufactured as small button-sized batteries. The mercury cell is used in calculators (Figure 21.15). Because of its very steady output, the silver cell is used in watches, cameras, heart pacemakers, and hearing aids. Their major disadvantages are toxicity of discarded mercury and high cost of silver cells. 

Soluble-cathode lithium primary batteries most times contain very toxic cathodes and flammable solvents. These types of batteries are seldom seen outside of the military in sizes larger than a button/coin cell. They are common in some heavy industrial or remote processes including oil-drilling operations. They are extremely common in many military forces throughout the world. 

Most of the commercial battery systems, e.g. zinc-carbon, manganese dioxide-zinc, nickel-cadmium, lead-acid and mercury button cells contain toxic substances. Strong efforts have been made to recycle these batteries, to lower the concentration of their toxic substances or to replace them with alternative systems. Nevertheless, battery production processes as well as disposal or recycling activities of spent batteries are responsible for the infiltration of a few toxic substances in our environment. The following chapters describe the toxicology of mercury, cadmium and lead, which are the most toxic components found in different battery systems. 

Gas-proof constructions are often designed like commercial batteries (including button cells), so they can replace the primary cells in portable electric and microelectric devices. Meanwhile, usage of nickel-cadmium batteries is strongly limited by law because of the dangers related to toxic cadmium. 

Miniaturized button batteries (all three dimensions below 8-10 mm) were used for hearing aids and similar small-sized appliances. For some time hearing aid batteries were based on the mercury-zinc system. Because of the toxicity of mercury compounds, the production and use of mercury-zinc batteries in many countries were held up and they are now replaced with silver-zinc or zinc-air batteries. 

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