(Bloomberg) -- AT&T Inc. shares hit an almost three-decade low Friday amid growing concerns of the potentially high costs the phone giant faces if it must clean up contamination due to lead-clad wiring throughout parts of its nationwide network.Most Read from BloombergSingapore Arrests Minister, Property Tycoon in Graft ProbeHow Much Income You Need to Crack America's Richest 1%DeSantis Says No Thanks to $377 Million in US Energy FundsBiden Administration to Forgive $39 Billion in Student DebtWa