SAN DIEGO -- Considered the largest secondary school system in the U.S., the Sweetwater Union High School District has grown over the last six decades to 41,000 students grades 7-12.

In 1920, the South Bay began to grow and the Sweetwater Union High School District opened.

But what do all of the schools in the district have in common?

"Almost all of the older schools had some type of asbestos in one form or another," said air conditioning technician George Gerber.

Gerber is a 17-year veteran of the school district's maintenance department and now a whistleblower.

"I've been to every single school, every single attic and every single under cross space and everything else," said Gerber.

Gerber said he has found asbestos in many areas, including those used by students and school staff.

Working undercover, the 10News I-Team collected samples on our own at Sweetwater High School and Montgomery High School.

The results were sent to a lab and the results confirmed that the material collected is asbestos.

In addition to samples, there were stacks of boxes containing years of records.

"I'm just a maintenance man trying to document ...," said Gerber, who has spent years tracking the problem.

He said he is frustrated because he has tried to convince his superiors that it is a bigger problem than they acknowledge.

But Gerber is ignored, so he seeks the I-Team's help.

"There are areas and rooms that I've been reporting for extended period of time that's almost gone on in two years that haven't been addressed."

Since 2000, South Bay voters have approved millions of dollars in bonds, including $8 million for asbestos work.

However, the problem persists.

"Just because asbestos is on campus doesn't mean it is a health hazard," said Lillian Leopold of the Sweetwater Union High School District.

It is not that important, Leopold said, because any school built before 1978 is going to have asbestos.

She said the type of asbestos can make a difference. Whether it's solid or crumbles in pieces, as long as it stays behind walls Leopold said, "Asbestos is not a problem unless it is disturbed …"

Gerber provided photos that would seem to show asbestos that was on the floor, exposed and not just behind the walls.

"Depending on the condition of the insulation, there could bed chunks of it. It could be crumbling. It could be a powder residue lying around," said Gerber.

By federal law, school districts are mandated to inspect its schools for presence of asbestos-containing materials.

10News filed an Open Records Act request for the two most recent reports.

The reported showed that 17 schools have asbestos on campus -- all safe, according to Leopold.

The district has to tell parents about the asbestos on the campus. If parents are concerned, they could visit the schools to see records describing what work has been done.

One former student went in to ask for this information and found that two of the 4 staff members knew about the records and two other staffers were clueless.

"They were like, 'Ah ... I've never heard of such a book. Not to my knowledge,'" said I-Team researcher Isabella Depierro.

Health experts said students should know if there are risks and where the risks are.

The school district said the law does not require specifics, and said notifying parents is enough.

"We don't need to tell them the information. We just need to tell them that there's a potential for exposure at the school," said Leopold.

Dr. Gordon Yung, director of advanced lung disease program at the University of California, San Diego Medical Center, said, "From a lung doctor standpoint, any asbestos is too much."

While Yung is not familiar with Sweetwater Union High School District's asbestos removal program, he is familiar with asbestos.

"By the time you have problems, it is usually 20, 30 years down the road," said Yung.

Today, it might not seem like a problem for the students in the district.

But who can say what will happen to them in the future?

That is why Gerber said he is willing to risk his job to tell this story.

"When it's said and done, I still want to be able to say that I did the right thing," said Gerber.

Newer schools like Eastlake High School and Otay Ranch High School are not affected because they were built using non-asbestos materials.

10News contacted the school board and local leaders in the South Bay, informing them of what was found.

10News will provide an update if new developments arise.