On Friday AT&T Inc. shares fell to an almost thirty-year low, off growing worries over the potentially high expenses the phone provider will face if it is forced to clean up lead contamination due to lead-clad wiring which has been used throughout parts of its nationwide network.

A Wall Street Journal story broke the issue earlier this week, revealing that lead cables which were a part of its early land-line networks, that were built by the phone companies in the first half of the 20th century, are now leaching lead into the environment. Several national carriers have since inherited those networks, including AT&T, Verizon Communications Inc. and Lumen Technologies Inc.

AT&T shares dropped 4.1% to $14.50 by the close in New York, as industry analysts have been trying to figure out what all of it may cost to clean up, as well as any legal risks which may be operant due to lead which has already leached out into the environment.

In a note Friday, JPMorgan analyst Phil Cusick wrote that “AT&T will have the largest exposure,” given that it service area covers roughly 40% of homes in the US, and it has an additional extensive long distance network. Cusick has cut his AT&T target price from $22 to $17 due to the uncertainty over the issue.

The lead problem is only the latest issue facing the nation’s largest phone company. The company’s free cash flow in April was reported at $1 billion, which substantially missed analyst estimates of $3 billion, triggering a second year in a row of worries over dividend payments.

The company also warned last month that it was seeing less wireless subscriber growth than it had anticipated. The company was also caught out attempting to obscure a massive restructuring and job reduction effort beneath a return-to-work policy.

So far, AT&T has declined to comment on the lead issue. Questions about the issue have been referred to USTelecom, an industry group. It has set up a web site which disputes the importance of phone cables as a source of lead exposure. However the group notes it is “ready to engage constructively on the issue.”