LANSING, Mich. (AP) — In proposing a tougher limit for lead in drinking water, Gov. Rick Snyder wants to lift Michigan from the depths of the Flint crisis to being a national model for lead monitoring that could help assess whether current rules are too lax.

Nearly 1,500 water systems serving 3.3 million Americans have exceeded the Environmental Protection Agency’s lead cap of 15 parts per billion at least once in the past three years. If Michigan’s proposed new standard of 10 ppb were applied across the country, that number jumps to more than 2,500 systems with 18.3 million customers — a fivefold increase, according to an Associated Press analysis of federal data.

Reducing the limit and adopting other proposed changes would give Michigan the world’s toughest protections “by far,” Virginia Tech University environmental engineering professor Marc Edwards said.

“This new rule is going to be very, very tough to meet, and it’s going to cost money. It’s a huge step forward if we’re able to pull it off,” said Edwards, who helped expose the contamination in Flint and devise Snyder’s plan.

Other steps would involve gradually replacing 460,000 lead service lines, strengthening sampling procedures to catch problems in the highest-risk houses and requiring testing in schools and daycare centers.

New York, Denver, Boston and Pittsburgh are among the cities that are within the current lead limit but would exceed the one proposed in Michigan. The number of violations would more than double in 19 states.

Snyder, who has apologized for his administration’s failures that caused and prolonged the Flint crisis, made the proposal on April 15. He called the current national rule “dumb and dangerous.”

The EPA limit has been in place since 1991 and was established based on what corrosion controls can reliably achieve, not on what is considered a safe amount of lead in water. The previous standard allowed for 50 ppb where water entered a distribution system.

If more than 10 percent of sampled high-risk homes are above the federal level, agencies must inform customers and take steps such as adding chemicals to prevent corrosion and potentially replacing underground lead pipes that connect to homes.

Supporters of a lower limit say it would bring Michigan and the U.S. in line with World Health Organization guidelines adopted by other countries, including Canada and members of the European Union. But water experts agree that the current EPA rule is more protective even though the standard is set at 15 ppb, compared with the international level of 10 ppb.

That is because the testing methods are different. The U.S. requires water samples to be taken at a time when lead is at higher levels. The international guideline allows for testing of running water that is more likely to show lower amounts of lead.

“It could miss temporary higher concentrations of lead in the water,” said Mike Keegan, an analyst with the National Rural Water Association.

About 80 countries and territories follow the WHO lead guidelines, which were established in 1993, said Gregory Hartl, an agency spokesman in Geneva. Using randomly timed samples gives a more representative exposure to lead while the U.S. method provides a worst-case estimate, he said.

The EPA plans to release new regulations next year to strengthen its lead rules.

Before the Flint crisis, an advisory council last year recommended adjustments to the current regulations but did not call for changing the limit of 15 ppb. Instead, the focus was on replacing millions of lead pipes and controlling corrosion.

In a statement, the EPA said the federal lead rule is supposed to “minimize risks” from lead “but does not eliminate them.” The agency said lead can still leach into water even when corrosion-control chemicals are used properly.

At a recent congressional hearing about Flint, EPA water regulator Joel Beauvais said many of the recommendations were developed before the disaster came to light. Since then, he said, the “understanding of where we need to go on this has evolved somewhat.”

Edwards supports a 10 ppb limit but also said the current federal standard is “quite tough” if enforced properly. He said how and where samples are taken is more important.

Yanna Lambrinidou, a medical ethnographer and president of Parents for Nontoxic Alternatives, helped develop Michigan’s proposal after writing a dissent to the advisory council recommendations.

Dropping the standard to 10 ppb, she said, would require more small- and medium-sized water systems — those with fewer than 50,000 customers — to do corrosion control. It would also trigger more frequent public notification about system-wide lead problems.

Other regulatory changes are more critical, she said, but the lower lead limit would be “fantastic” because “there are so many holes in this rule.”

While a couple of states have tougher customer-notification requirements than required federally, Michigan is the only one to consider a comprehensive overhaul of regulations.

Members of Congress also are seeking reforms in the wake of Flint.

Bills sponsored by Reps. Tammy Duckworth and Mike Quigley, both Illinois Democrats, would trigger protection for individual households with lead levels exceeding the amount that would raise an infant’s blood level above 5 micrograms per deciliter. The legislation would also spend $300 million for pipe replacement and other improvements.

Democratic Rep. Gene Green of Texas said going to a 10 ppb limit would help, as would more robust monitoring of tests to prevent water systems from cheating. He expressed concern that the EPA is taking too long to finalize its new rules.

“It’s not just Flint. Human action caused Flint,” Green said. “But there are systems all over the country that have high levels of lead that need to be dealt with.”