Lead, cadmium, and mercury are known toxins, causing cancer and neurological disorders. Most batteries end up in landfills or incinerators, where these toxin are released into the environment. When these materials make their way into the food chain, they cause serious harm to humans and animals. For these reasons, batteries containing more than trace amounts of these substances will be banned in the European Union by 2008.Look for batteries that contain trace amounts of these materials or less, and be sure to dispose of batteries properly.