The lead-pipe danger lurking underground

Households across the country may be at risk of drinking lead-tainted water as lead pipes age underground and municipalities struggle to balance high replacement costs with a slew of other urgent infrastructure projects.

Why it matters: Exposure to any amount of lead is highly dangerous, especially for children. The public health disasters in Flint and Newark have dominated headlines, but more than 6 million lead service pipes are buried beneath U.S. cities — and the Government Accountability Office believes that's a low estimate.

• Those lead pipes are being replaced at an average rate of 0.5% a year.
• According to the nonprofit American Water Works Association (AWWA), upgrading and replacing all U.S. water systems would cost more than $1 trillion through 2035.
• In Flint alone, replacing 10,000 lead service lines is expected to cost $80 million.

Driving the news: Recently, elevated levels of lead have been detected in drinking water in some schools in North Carolina and Tennessee, and some homes in Alabama and east Texas.

• These warnings didn't go beyond local newspapers, so it's easy for many people to think lead pipes are only a problem in older industrial towns like Flint and Newark.

How it works: Water systems are able to chemically control the corrosion of lead pipes to prevent lead from seeping into tap water. But changes in water source or treatment can cause lead to spike.

• In Flint, lead levels increased in 2014 when it switched its water source to the Flint River, which was not treated with the anti-corrosive orthophosphate.
• In Newark, the city discovered this year that its anti-corrosion efforts weren't working for one of it main water supplies. The city told about 15,000 households to drink only bottled water and handed out water filters, although the EPA warned they may not be working, per the AP.
• Another complication: Utilities monitor the quality of water when it leaves the treatment plant. But lead fittings and pipes can contaminate water between the plant and a resident's faucet. So many communities are pushing for in-home testing to ensure lead levels are under federal limits.

Where it stands: The recent crises have generated enough public awareness about lead pipes that residents are pressuring utilities to replace lead lines.

• Splitting the costs of replacements is tricky since lines are on both public and private land. Utilities and home owners don't always see eye-to-eye on who pays for upgrades, as Pittsburgh found out last year.
• And utilities don't always know where lead pipes are, leaving many to guess based on the age of a house.

"Overall, we're always making progress because every lead pipe that gets replaced is one fewer in the ground. But the progress is really slow."

The big picture: 12 states have more than 200,000 lead pipes in their water systems, according to a 2016 national survey by AWWA.

• Three more — Pennsylvania, Iowa and Kansas — have more than 100,000.
• Every state, and Washington, D.C., has at least a few thousand lead lines.
• Altogether, AWWA research estimates that 15 million to 22 million people nationally have lead service lines supplying water to their homes.

The cost of replacing lead pipes typically ranges from $3,000 to $5,000, a cost that's prohibitive for most low-income households. Rebates and tax hikes have been funding options. For example:

• Madison, Wisconsin became the first major U.S. city to completely replace all lead service lines, offering rebates to residents to cover half the replacement cost.
• Lansing, Michigan, replaced lines funded by water rate hikes.
• The Massachusetts Water Resources Authority in 2016 launched a $100 million interest-free loan program to help towns in its service area replace lead service lines.

The bottom line: Water systems are just one part of the aging infrastructure puzzle that cities are trying to manage, upgrade and replace.