MALIBU CITY HALL — Malibu High School is safe, federal and state health officials said Thursday night as parents demanded answers, concerned that their children could be exposed to cancer-causing toxins.

More testing, including soil testing, will be performed, officials with the Environmental Protection Agency and state Department of Toxic Substance Control said during the Board of Education meeting.

Dozens of people showed up at Malibu City Hall for the meeting, during which board members, district officials, and parents asked questions of officials from the EPA and the DTSC for more than three hours.

Concerns about contamination arose in October after it was made public that three teachers had been diagnosed with thyroid cancer. Afterwards, 20 teachers sent a letter to the district complaining of health issues and questioning the safety of the campus.

One building was closed shortly thereafter and the district tested the air, caulk, and dust particles in rooms for PCBs, a contaminant linked to cancer. The air was deemed safe by the EPA, but several samples of both the caulk and dust contained PCB levels high enough to trigger the agency’s involvement.

One caulk sample, which was found to have 37 times the amount of PCBs that the EPA deems acceptable, was revealed to have been taken from an exterior window at the library. The library is currently in use by students and staff but this doesn’t pose an immediate threat, said EPA representative Patrick Wilson, because the air samples have been found to be safe.

“People do not have an increased risk of illness or of developing illness because of the contaminated caulk,” he said. “What occurs ‚Ä¶ is that the caulk is the primary contaminant and it contaminates secondary sources: the air, perhaps the soil.”

The caulk poses a long-term threat because as it degrades it will contaminate the air, he said.

DTSC representative Tom Cota said his agency would be taking soil samples to test for a number of contaminants. PCBs were discovered in soil on campus in 2010 and the district hired a private company, Arcadis, to perform soil remediation. Because the district did not use state funds, they were not required to seek DTSC oversight. But, Cota said, Arcadis did a good job documenting its work and the results do not throw up any red flags.

“The soil, it had some residual PCBs,” he said. “Where it came from, I don’t really know. I don’t know if we’ll ever really know. But it did not present that significant of a risk.”

When asked if it was safe for students to be digging in and eating from a community garden located on-campus, the experts did not give a definitive answer because the soil testing was only performed in a small area.

The Los Angeles Department of Public Health official who was supposed to join the other panelists was not able to attend the meeting, but a representative of the Malibu parents asked the EPA officials to explain the teachers’ illnesses.

Wilson, an EPA toxicologist, pointed out that one in three Americans are diagnosed with cancer. Thus far, he said, the data does not show that the PCBs are to blame.

“When we compare the maximum concentration from the limited data set, and all the caveats that we’ve attached to it, it just doesn’t seem that the concentrations in the air are anywhere close enough to be associated with the health effects that are associated with PCBs,” Wilson said.

Board members, particularly Ben Allen, grilled the officials on the specifics of the science. Board member Nimish Patel asked the consultants if they would feel comfortable sending their children to Malibu’s campus and all responded affirmatively.

One teacher asked if students could begin reentering classrooms not associated with sickness or high PCB levels, noting that relocation has been detrimental to their education.

“We wouldn’t have any objections to the teachers or the children moving back into those rooms,” said Steve Armann, an EPA representative said.

A handful of concerned parents spoke during the public portion of the meeting, accusing the district of negligence and a cover-up. Only a few took a combative tone, but these speeches were met with applause.

Earlier this week, the district released an official request seeking an engineering consulting firm to test and evaluate the campuses for contaminants. The EPA and DTSC will oversee the testing. Responses from firms are due by Dec. 20 and a selection will be made in January.

Because PCB levels triggered the EPA involvement, EPA’s oversight will be paid for by federal tax dollars. DTSC will charge for its oversight.

dave@www.smdp.com