TRENTON, N.J. — An environmental watchdog group said Monday it found excessive amounts of lead in several brands of artificial turf, and it warned some of the biggest manufacturers and sellers that it will sue unless they recall or reformulate their products.

TRENTON, N.J. — An environmental watchdog group said Monday it found excessive amounts of lead in several brands of artificial turf, and it warned some of the biggest manufacturers and sellers that it will sue unless they recall or reformulate their products.

The report from the Center for Environmental Health comes after New Jersey officials found unacceptably high lead levels in some synthetic surfaces and federal authorities recommended lead testing on fraying sports fields.

The center's tests, which it hired an independent lab to verify, went beyond sports fields. They found excessive lead in indoor/outdoor carpeting, artificial lawns and playground grass made with nylon and polyethylene, said Charles Margulis, a spokesman for the group.

The group classified the amount of lead as excessive if it exceeded 600 parts per million, which is the maximum allowable in paint. About 50 products were tested, and at least 15 were found to have high lead levels.

In one test, the lead was so accessible it could be wiped away with a cloth, according to the Oakland, Calif.-based group that focuses on identifying toxins in everyday consumer products.

Testing by the New Jersey Health Department found high lead levels in nylon and nylon-blend fields, but only in fields that had endured a lot of wear. The lead found at three New Jersey turf fields could be absorbed by humans, a follow-up test showed, but the state epidemiologist said the lead levels were not high enough to cause poisoning to people who play on the fields.

Margulis said the center has begun notifying 15 turf manufacturers and retailers of its intent to sue under California's Safe Drinking Water and Toxic Enforcement Act unless the companies agree to recall the products or reformulate artificial turf so it contains less lead.

Names on the list include some of the country's largest retailers, like Ace Hardware and Lowe's, and some of the best-known turf manufacturers, like AstroTurf. The companies have 60 days to respond.

Davis Lee, a Georgia Tech professor and consultant to turf manufacturers, said he was skeptical about the latest results.

"Their results are not consistent with what I've seen," he said. "I've done several months worth of testing. I've not seen anything that would raise a concern."

Rick Doyle, president of the Synthetic Turf Council, an industry trade group, said the lead in turf is encapsulated in the blades and does not leach out or become airborne.

"It does not pose a risk to human health or the environment," Doyle said. "It is not readily absorbed by the body or released into the environment."

Messages left with Ace, Lowe's and AstroTurf weren't immediately returned.

Earlier this month, AstroTurf issued a statement saying additional tests by the New Jersey Department of Health and Senior Services confirmed the safety of synthetic turf fields.

The United States has about 3,500 synthetic playing fields made of various materials, including nylon and polyethylene, and about 800 are installed each year at schools, colleges, parks and stadiums, the Synthetic Turf Council has said.

Pigment containing lead chromate is used in some surfaces to make the turf green and hold its color in sunlight. It is not clear how widely the compound is used.

Lead can cause brain damage and other illnesses, particularly in children.

Health officials say the main risk is cumulative exposure. While it is unlikely that anyone will play on a turf lawn or field once and sustain an excessive lead exposure, the risk of health problems rises with repeated exposures.

The government has no standard for how much lead is allowable in artificial turf.