Joe Fabrizio tried to stay calm when he learned the day-care center he used was contaminated.

His 4-year-old son seemed fine, despite revelations that Kiddie Kollege was once a thermometer factory and was saturated with mercury vapors. Besides, the results of the child's urine test were negative, and New Jersey health officials were saying the children who attended the Gloucester County day-care unit likely would not suffer long-term effects.

"I didn't want to overreact," said Fabrizio, 44, a self-employed mason who lives in Buena with his wife, Patty, and their three children.

Three years later, the Fabrizios are terrified. Their son had to repeat kindergarten, and they just got word he may be held back again. He has memory lapses and trouble focusing. A few weeks ago, a school psychologist suggested he might have organic brain damage.

Though no clear link can be made between the child's problems and his exposure to mercury, questions nag at the Fabrizios. Were they misled? What should they do? Who can help?

Tina Toy, a Kiddie Kollege parent who maintains a Web site for the parents of nearly 100 children and babies who attended the day-care center between January 2004 and July 2006, said many were still "hungry for answers." Parents are haunted by the worry that one day, their children could develop a problem because they breathed toxins while their brains were growing.

Mercury can cause neurological, kidney, and skin problems, and some doctors compare it to lead as a serious threat to children's health.

Doctors at Mount Sinai Pediatric Environmental Health Specialty Unit in New York, who advised the New Jersey Health Department after the day-care center was closed, say they doubt the children's health is at risk because the mercury levels found in their urine tests were elevated but not extremely high.

What concerns some Kiddie Kollege parents, however, is that no one knows exactly how much mercury their children inhaled in the months before the test was given. Fabrizio's son left Kiddie Kollege two months before it was shut, and his body had time to excrete any mercury he may have taken in. He had been going there for a year.

The Department of Environmental Protection later tested the center and found the walls, floors, and ceilings of the one-story block building were emitting mercury vapors at 27 times an acceptable indoor level.

Joel Forman, a founder of the Mount Sinai unit, agreed that the urine test only measures the amount of mercury that was currently being excreted. But the overall results of the Kiddie Kollege children's tests, he said, are reassuring.

"No one can ever answer the question of what the exposure might have been before the test was taken," Forman said. "But when there's no evidence, you have to deal with the health issues the child has and focus on those."

The children's levels were far below what Forman found in nine children from Yonkers, N.Y., who were hospitalized in 1998 after they banged a large globule of mercury with a hammer and watched the droplets fly. Their mother vacuumed the mess up, turning the droplets into dangerous vapors.

Forman said the DEP report of the mercury levels inside the building was not "meaningful" to the children's health. It likely depicts a worst-case scenario when all the windows were sealed and the temperature was raised.

The report also found the highest concentration was in the basement, to which the children had no access.

Toy said other parents had moved on with their lives and were trying to put what happened into perspective. Toy finds herself waffling between both groups, one day confident that everything will be fine, the next day frightened about the future.

"There are still those thoughts in the back of my mind," Toy said.

Three years ago, Toy took her daughter, then 2, to Children's Hospital of Philadelphia to see whether the girl's behavioral problems might be from mercury poisoning. Toy said a psychologist there examined the child, provided a parenting book, and told her there are many reasons a child acts out.

"Kids will be kids," said Toy, summing up what she learned. The psychologist felt the mercury was not an issue.

Still, Toy and the other parents would like medical monitoring for all the children to make sure a pattern does not emerge as the years go by. They have filed a lawsuit seeking an order to have doctors periodically check for developmental problems and any abnormalities and to make sure the children get the care they need.

The lawsuit asks that Franklin Township, the DEP, the Gloucester County Health Department, the building owner, and others pay for the monitoring, saying they collectively allowed a day-care center to open inside a toxic building.

"These children should have been tested the last three years, and I have no way to do this except through the court system," said Joe Osefchen, one of the attorneys.

He said some parents could not afford to have their children checked.

The lawsuit also names Jim Sullivan Inc. and others who acquired the abandoned factory in a tax sale and then rented it to a day-care center. Jim Sullivan 3d, a principal in the firm, has said he misinterpreted a report that mentioned the building was contaminated.

Soon after it was shut, a few parents reported that their children had experienced seizures, rashes, and peeling of skin on their fingers and toes - all symptoms of mercury poisoning.

Fabrizio, however, said that his son was healthy and that he trusted the state Health Department. Now, he said, he believes medical monitoring would help his son, but he fears it might come too late. No trial date has been set.

For the last two months, he has been searching for answers on the Internet, poring through documents, and leaving messages for specialists.

Fabrizio recalls how his son used to sit on his lap as a toddler and work the levers on his backhoe.

"He's 7 now, and can't put it together to do that anymore," said Fabrizio, who asked that his son's first name not be used. "He forgets in baseball whether he bats right or left."

"I don't have a year to waste finding someone who can treat my son. This is something that's rare," he said.

His wife also feels their problem is urgent.

"All this time has passed, and we didn't know there was something wrong," said Patty Fabrizio, a dialysis technician for Kennedy Memorial Hospitals.

Fred Henretig, director of clinical toxicology at Children's Hospital, said there were various treatments for exposure to environmental poisons. But with mercury, the urine tests normally point the way, he said.

If the tests indicate high levels, Henretig said, the children might receive chelation, a treatment that removes mercury, lead, and other heavy metals from the body.

"But it's not something done willy-nilly just to be on the safe side. You definitely reserve that for someone with verified significant mercury exposure," he said, because there are risky side effects. "If there are no signs of serious exposure, I'd try to talk someone out of it."

Henretig said he had not treated any of the Kiddie Kollege children. But he said parents' minds "should be put at ease" because their test results showed minor exposure.

Though the building may have recorded high levels of toxins, exposure depends on whether it was 24/7 or just part time, and where the highest concentrations were. He also said he believed it was unlikely children might develop "delayed brain damage" if they had no symptoms when they attended the center.

"It's hard for me to blithely say the parents are making themselves crazy for nothing, because these people went through a very frightening experience," Henretig said. "But we all worry a little bit about what has happened to our children in the past and there are so many things we could worry about, like the BPA in plastic bottles, and cigarette smoke, and other environmental contaminants."