WILLOWBROOK, Ill. (CBS) — A teenage girl has been fighting two different cancers much of her life, and her family believes a Willowbrook company emitting a toxic gas in their neighborhood is the cause.

The allegations center around Sterigenics. The family of the girl, Yasmeen Harrison, said they fear she was exposed to ethylene oxide while attending nearby schools.

CBS 2 Investigator Dave Savini has been probing Sterigenics for a year. Yasmeen’s story is his latest.

“She means everything to me,” said Yasmeen’s father, Ivan Harrison III.

Yasmeen has been in and out the hospital since she was 2 years old. The hospital is where some of her favorite childhood memories were made.

The Willowbrook teen celebrated her sweet 16th birthday this summer, and is excited about the start of a new school year.

After numerous surgeries and treatment for multiple cancers including leukemia and kidney cancer, Yasmeen is slowly getting back to solid foods. Her favorite food is pizza, her favorite place to have it MOD Pizza in Willowbrook.

And Yasmeen likes “pesto saucy, mushroom, sausage, salami, a barbecue drizzle, diced tomato,” all on one pizza.

“She loves to load it,” her father said.

But while Ivan Harrison III loves to see Yasmeen happy, he knows deep down every day, she’s in pain.

“When she was 2, she was initially diagnosed with acute lymphoblastic leukemia – ALL,” he said.

It is a disease he now blames on the medical supply sterilization company down the road, Sterigenics.

“No one could ever tell us the cause of why she got leukemia, relapsed, and later got kidney cancer,” Ivan Harrison III said.

Yasmeen’s cancer battles resulted in two bone marrow transplants, repeated rounds of chemo and side effects.

It wasn’t until high levels of ethylene oxide were found during ambient air testing near their home, and all three of the schools Yasmeen attended, that they began to understand what was in the air their daughter was breathing.

“It was very surprising to me that a company that was emitting that kind of chemical could even be in an area this residential,” Ivan Harrison III said. “I just couldn’t even believe how that could happen.”

They now believe her cancers are directly related to ethylene oxide emissions.

“It is known human carcinogen,” said Dr. Peter Orris, a professor of environmental and occupational health sciences at the University of Illinois at Chicago. “There are very few known human carcinogens that have been accepted by the World Health Organization; by governmental organizations; the U.S. EPA; the European. This is one of the few. Some of the others are cigarette smoke; are asbestos.”

Matt Haller gave CBS 2’s Savini an interview a day and a half before he died this past March. He is one of about 43 litigants whose lawsuits have been filed against Sterigenics in state court, accusing the company of causing cancer.

The company has repeatedly denied CBS 2’s requests for an interview, but say they followed and outperformed all regulations. In a statement, Sterigenics said they “intend to vigorously defend against claims, and are confident (the) Willowbrook facility is not responsible for causing illness.”

“To just think that, wake up one day and that this company could have been literally behind my death is shocking,” Haller said in February. “It’s utterly shocking.”

Questions about whether illness are linked to ethylene oxide, in part, date back 35 years.

The CBS 2 Investigators obtained a 1984 letter written by the Illinois Environmental Protection Agency, warning the company – then Griffith Laboratories – warning of cancer dangers associated with ethylene oxide.

The letter listed cancers of the pancreas, bladder, brain, central nervous system, and stomach.

Haller had stomach cancer.

Since February, the CBS 2 investigators have also been speaking with whistleblowers who claim the company knowingly released the gas into the atmosphere.

“The chambers would run different cycles. They would leak gas a lot of times. I swear to God,” Mike Morales, who worked at Sterigenics as a forklift operator at Sterigenics nearly two decades ago, said in a February interview.

The plant was shut down in February with a seal order by the EPA, but now is in the process of reopening one day under new restrictions. A law named after Matt Haller requires the company to capture 99.9 percent of all ethylene oxide used.

“I believe the chemical from Sterigenics caused Yasmeen’s leukemia, and I’m going to court and I intend to prove that,” said Yasmeen Harrison’s attorney, Shawn Collins.

Collins is filing a lawsuit against the company on behalf of Yasmeen. He says the child’s exposure began through her mother – who grew up in the same Willowbrook house they still live in today.

In other words, he believes Yasmeen’s exposure to ethylene oxide began while she was still in her mother’s womb.

“Yasmeen’s mother was exposed to ethylene oxide day after day after day after day while she was carrying Yasmeen,” Collins said.

Her father said no level of ethylene oxide should ever be allowed, and now worries for all the other kids in the area.

“It’s just too close, and it’s exposing too many people,” Ivan Harrison III said. “You know, young innocent kids.”

A lawsuit on behalf of Yasmeen Harrison was filed Tuesday night against the company. Hers is the 44th case that we know about to be filed.

The cases have been filed in the Circuit Court of Cook County.

Meanwhile, Yasmeen is now in remission.