CLEVELAND -- You may have never heard of Thimerosal, but if you or your children were vaccinated before 1999, chances are, it was injected into you.

The mercury preservative has sparked a medical controversy because some people claim it may be responsible for an increase in autism, reported 5 On Your Side's Curtis Jackson.

"I truly knew something was wrong when he was about 15 months," said one parent.

Another mother said, "He would have great eye contact and then he just kind of seemed to disappear."

And yet another mom said, "I gave my son mercury and I will never get over that."

These local mothers are describing their children's sudden onset of autism, which they say began after their kids were immunized.

"I know what happened to my child. I've got videotape, pictures showing my child was normal -- hit his milestones, did this and then all of the sudden, something just happened," said mother Cheri Henry.

These women believe their children's autism was caused by Thimerosal, a preservative widely used in vaccines until 1999.

Thimerosal is almost half organic mercury, which can cause brain injury or death in sufficient amounts.

For years, it was not only used in vaccines, but in many over-the-counter medicines.

Still, Thimerosal went largely unnoticed until the 1990s, when more immunizations were added to the schedule.

"From that point on, we had an unbelievable epidemic of autism," said Dr. Mark Gier.

Gier, a Maryland geneticist, and his attorney son David, are leading proponents of the theory.

Their controversial research, featured in the book "Evidence of Harm," argues mercury in Thimerosal caused autism in children who are genetically susceptible.

The Giers call it the Thimerosal Generation, autistic children who might otherwise be normal had they not received vaccines with Timerosal.

"We've absorbed more damage than we took during World War II, World War I and the AIDS epidemic and 9/11, all combined," said Mark Gier.

But Dr. Max Wiznitzer, a nationally recognized autism expert at Rainbow Babies and Children's Hospital, says the Giers' theory is wrong.

"The first flaw is, you can't say that one causes the other, and people are saying that," said Wiznitzer.

And Wiznitzer is not alone.

A panel convened by the Institute of Medicine last year rejected the Giers' research as "uninterpretable," adding it "provided no information."

Last year, it outright rejected any cause-effect relationship between Thimerosal vaccines and autism.

"We've still seen the same rise in the number of individuals identified as having autism spectrum disorders even though Thimerosal is no longer in the immunization program," said Wiznitzer. "Obviously, if it was a cause-effect relationship we would expect the opposite to occur."

The Giers defend their work, saying autism rates have not gone up, but have gone down since the removal of Thimerosal five years ago.

"What we've seen is that children born after 1999 have significantly less autism and other neuro-developmental delays than children born before in the Thimerosal generation," said David Gier.

Caught in the middle of the Thimerosal debate are a growing number of local parents of autistic children who, despite having science against them, are part of a mercury movement.

Using the Internet, they inform one another about new research and treatments they say prove mercury Thimerosal causes autism in some children.

For most, follow-up government studies are nothing more than an elaborate cover-up by vaccine manufacturers.

"They know what's going on, and they could have come out and told people this is what's happening," said mother Tina Hamilton. "This is what you can do to help your children, and they didn't do it."

Jane Milota, who has a child with autism, said, "Let the scientists do an independent study that can either prove or disprove this theory."

While the Institute of Health is critical of the Giers' research and has ruled out a cause-effect relationship between autism and vaccines, it admits very little is known about the mercury that's in Thimerosal.

Research by more credible autism experts is under way in New Jersey.

However divided the debate, both sides agree that Thimerosal should be taken out of vaccines.

For the most part, manufacturers have complied, though it still remains in two out of four flu shots.