High lead levels found in artificial turf at both of Northern Valley Regional’s high schools have prompted school officials to close the fields indefinitely.

The results came just a week after state officials recommended that the federal government investigate nearly 4,000 artificial turf fields in use nationwide, following sample tests that found lead at three fields in New Jersey.

That round of testing did not include Northern Valley, which tested its fields independently.

Now, more testing of the fields at the Demarest and Old Tappan locations will be done to determine how serious the problem is and whether the fields might need to be replaced.

“We want to take every precaution to find out exactly what we have… before we let anybody go back on the fields,” said Ray Jacobus, the assistant superintendent for business.

State health department officials say children would need to have prolonged contact with the fields as well as exposure to lead in other settings before their health would be at risk. Inhaling or ingesting lead can cause brain damage and other neurological illnesses, state health officials say.

“The main concern is the cumulative effect of a child being exposed to lead from a field when also exposed to lead at home,” said Marilyn Riley, a Department of Health and Senior Services spokeswoman. “That’s where more of the concern is.”

Concentrations of lead in fibers from the green-colored synthetic turf at the Demarest school’s field were about 15 times the state standard for residential soil — 6,300 milligrams of lead per kilogram of fiber over the state standard for soil of 400 milligrams of lead. A sample taken of the green turf fibers of Old Tappan’s field was 10 times the state standard.

The state recommends restricting the use of fields for children under the age of 7. If the fields are used, they should be watered down to suppress dust and hand, body and clothes should be washed thoroughly. The most conservative recommendation is to close the field.

A statement by FieldTurf Tarkett of Montreal, Canada, which installed both Northern Valley fields six years ago, said the company was “astonished’’ by the findings, given that the state health department tested 10 FieldTurf fields this spring and found “very low or undetectable levels of lead.’’

“As an industry leader in the synthetic turf industry with more than 2,500 installed fields around the world, FieldTurf is fundamentally dedicated to the health and well being of everyone who plays on our fields,’’ the statement reads.

FieldTurf is working with the Northern Valley to verify the results and wants to conduct its own tests, said spokesman Elliot Sloane.

The field closures could mean finding new on-campus locations for graduations on June 19 in Demarest and June 20 in Old Tappan, said Superintendent Jan Furman.

Four turf samples from each school’s field on May 21 were tested, said Gary Leverence, president of Environmental Remediation & Management, Inc. of Trenton. Each field had one sample with elevated lead levels. The results showed the lead is contained within the product used to dye the fields green, he said.

When she received the results on Friday, Furman closed the fields, which cost $700,000 each to install.

ER&M is performing more tests at the two fields: of the sand underneath the fields to determine if lead has leached beneath the turf and on dust from the field, which is collected from shoes. Results should be available by the end of the week.

Northern Valley hired ER&M after the state tested turf from about a dozen municipal parks and colleges and found elevated levels at fields in Hoboken and Ewing. A Newark field tested for high levels last summer. The turf was replaced at those sites.

The turf industry contends the potential harm to children is overstated.

Lead chromate has been used in some dyes to keep the green color of the blades from fading in the sunlight. The industry is moving to phase lead out as an ingredient, said Rick Doyle, president of the Synthetic Turf Council.

But Doyle said experts hired by the industry have determined that the lead chromate in the fields is insoluble and encapsulated, meaning that it won’t leach into the soil below and can’t be absorbed into the body.

The industry claims that a 50 pound child would have to ingest 100 pounds of synthetic turf to be at risk of absorbing more than the recommended standard for lead, Doyle said.

“At the end of the day, we are still saying that this turf is safe,” Doyle said.

Parent Peggy Blumenthal, whose 17-year-old son Sean has played soccer on the Demarest turf field, said state and federal agencies should have required lead testing statewide long ago.

“If state is coming down now saying we think there’s a problem, why didn’t they come down six years ago and do the research before it’s a problem, before everybody has it down?’’ she asked.

“What are we supposed to do as parents?’’ said the Haworth resident. “Do I take my child for lead testing? Do you get a blood test or urine test? What are you supposed to do? Accept it and see what happens 10 years down the road?’’

GRASS VS. SYNTHETIC

A debate has been raging for several years in the United States and Europe over whether artificial turf improves or worsens the environment.

Pro

* Minimal watering needed, only on hot days to cool playing surface.

* No fertilizer runoff into surrounding waters.

* No need for weedkillers and other pesticides.

* More than 25 million tires kept out of landfills, crushed and used as fill on synthetic fields.

Con

* Chemicals. Activist groups call for more testing of not just lead content but of whether the chemical ingredients in crumb rubber can leach into the environment, give off gas or be ingested when they get on children's hands.

* Runoff. Water flows off turf just like pavement, creating another impervious surface that could potentially damage surrounding wetlands and streams.

* Ground warming. Turf fields can overheat on hot days, creating mini heat islands.

* Disposal. When fields wear out, the fake grass and other materials likely will end up in landfills.