The national debate stirred by high levels of lead discovered in the water supply in Flint, Mich., has flowed into Philadelphia.

Public health advocates this week said Philadelphia and other cities were failing to follow federal guidelines as they monitor lead levels at high-risk homes.

Up to 50,000 homes in Philadelphia are connected to city water mains by lead pipes, according to city officials.

Though lead service lines were banned in 1986, they remain in older homes whose owners can't afford to pay for improvements. Water flowing through lead pipes can pick up measurable amounts of the toxic metal.

According to the health advocates, the city is using antiquated testing methods that underestimate the amount of lead coursing through the plumbing.

There's some merit to their case, said a Philadelphia Water Department official. But there's no reason for alarm.

"If you want to panic, there are things to panic about and it's not this," said Gary Burlingame, director of the Water Department's Bureau of Laboratory Services.

"Are the testing methods outdated? Yes. Could Flint happen here? No, it couldn't."

Flint, Burlingame said, is dealing with a financial emergency, turmoil among city leaders, and a state takeover. Flint's crisis was created in a misguided effort to save money by changing the water source from Lake Huron to the Flint River.

High levels of lead pose a serious threat to bottle-fed infants, young children, and pregnant women. Blood-lead levels in children, which are checked by physicians, have been declining in recent years, according to the Pennsylvania Department of Health.

One-fourth of Philadelphia children were checked in 2014; the percent with high levels was just above the state average.

Children under the age of 6 are especially vulnerable to lead poisoning, which can cause permanent learning disorders and antisocial behavior. Since leaded gasoline was banned decades ago, the biggest source has been crumbling paint chips in homes dating from before 1978, when lead was banned in paint.

To prevent the metal from leaching from pipes, the city adds an anticorrosive to the water supply. But the city's responsibility should not end there, said Washington-based public health advocate Yanna Lambrinidou, who served on an Environmental Protection Agency panel on drinking water.

"You can minimize the corrosiveness, but you can't eliminate it," said Lambrinidou, who teaches engineering ethics at Virginia Tech. She developed a course based on a 2004 water crisis in the national's capital. "There are conditions that cause leaching of lead that have nothing to do with the water. The water utility can't prevent that."

Heavy street traffic, renovations at neighboring properties - even repair crews working on water lines - can cause additional lead to be released into the water supply, she said.

Spikes in the toxic metal often aren't found, she said, because when the city tests, it takes steps such as flushing water from pipes before taking a sample.

"Philadelphia is not duplicating real-world conditions when it tests," she said. "If you were to take Philadelphia Water Department protocols and go to Flint, Flint would probably pass the federal requirements with flying colors."

Burlingame said the Water Department complies with federal regulations, but the rules were meant to take the measure of an entire city water system, not individual homes. He agrees they could be more stringent.

Until that happens, Burlingame recommends steps concerned residents can take to minimize lead from the taps. If possible, he said, homeowners should hire a plumber to inspect their service line.

Failing that, he said, "use well-flushed water and don't use hot tap water to drink," as warmth tends to leach out lead from pipes and plumbing joints.

"After you've been showering, or after using a lot of water, fill up a clean pitcher and stick it in the refrigerator. Now you have well-flushed water from the street main."