The PBT of greatest concern in cell phones is lead, a heavy metal recognized as a problem material throughout the world. Lead is a suspected carcinogen, has adverse effects on the central nervous system, immune system, and kidneys, and has been linked to developmental abnormalities. Its main application in cell phones and other electronic products is in the solder used to attach components to each other and to the printed wiring board.

These persistent, bioaccumulative toxins, or PBTS, have been associated with cancer and a range of reproductive, neurological, and developmental disorders. They pose a particular threat to children, whose developing systems are especially vulnerable to toxic assault. Most of the persistent toxins and PBTs contained in cell phones are in the printed wiring board and liquid-crystal display.