The toxic morass that was America’s nuclear weapons complex is no secret. Hazardous conditions in places like the Portsmouth Gaseous Diffusion Plant  in Ohio moved Congress in 2000 to create a compensation program for former workers who developed illnesses that may have been caused by radiation or chemical exposures.

The program, run by the US Department of Labor, assumes that conditions significantly improved at nuclear sites after 1995 and processes claims accordingly. A new report by federal health investigators, however, casts doubt on that assumption.

The report from the National Institute for Occupational Safety and Health, dated December 21, 2015, summarizes the results of a NIOSH inspection at Portsmouth begun two years earlier. The Center for Public Integrity, which highlighted historical problems at the site in an article last month, obtained it this week from a former worker.

The most notable finding: air sampling in Building 326 of the now-closed uranium enrichment plant, undergoing decontamination and decommissioning, showed the presence of hydrogen fluoride, a potentially lethal gas, in concentrations up to 30 times the NIOSH “ceiling limit,” described as “a value that should never be exceeded.” Apart from its capacity to kill, hydrogen fluoride, commonly known as HF, can cause chronic lung disease, skin damage and blindness, according to the Centers for Disease Control and Prevention.

Investigators also noted that there was no sampling for nitrogen dioxide, another dangerous gas. Acute effects of exposure include vomiting, labored breathing and dizziness, according to the CDC; there also can be long-term effects on the immune system and the lungs.

Hydrogen fluoride, a remnant of production in Building 326, can be unleashed by the cutting of pipes, compressors and converters. Nitrogen dioxide is generated by the cutting itself.

The NIOSH team met with 16 people who worked at Portsmouth at the time, 10 of whom “expressed concerns about poor communication between management and employees and concerns about retaliation for reporting safety problems,” the report says. “Concerns included having inadequate information about chemical(s) used, chemical exposures, and potential health effects.” Five workers reported rashes they believed to be work-related.

“Several employees expressed concern that they felt rushed to complete job tasks and that some managers placed production goals ahead of safety,” the report says. “Employees believed these problems have led to near misses and accidents.”

The Energy Employees Occupational Illness Compensation Program is intended to provide payments to and cover the health care of people harmed by working at nuclear-weapons sites. Many claimants and some members of Congress find the program deeply flawed and question the Labor Department’s rationale for denying claims.

A year-old department circular directs claims examiners to presume that no significant exposure to any toxic agents occurred after 1995 unless there is “compelling data to the contrary.” Advocates who have pushed the Labor Department to reverse the policy say the NIOSH report is the latest example of recent problems. They worry about undocumented hazards going unnoticed.

“This is probably not an isolated incident,” said Deb Jerison, director of the Energy Employees Claimant Assistance Project, whose physicist father worked at the Mound Laboratory in Ohio and died of bone cancer. “If people don’t look, they won’t find.”

Labor Department spokeswoman Amanda McClure said the NIOSH report doesn’t require a policy change.

The department’s circular, based on Energy Department efforts to improve safety throughout the weapons complex, “does not negate the fact that there may have been higher levels of exposures at certain sites in individual cases after 1995,” McClure wrote in an email. The agency “takes those circumstances into account when they arise, and we will take NIOSH’s Portsmouth facility report into consideration on a case-by-case basis.”

The dismantling of the Portsmouth plant involves more than 2,000 workers and is being overseen by Fluor BWXT, a contractor for the US Department of Energy. In a letter to NIOSH dated December 3, 2015, Fluor BWXT said it has “robust” industrial hygiene and hazard-communication programs and closely monitors workplace hazards. The company said it had taken more than 57,000 air samples for radiological hazards in Building 326 since 2012. These samples, combined with urine testing, “have shown no reportable internal exposures” to workers, it said.

In an interview, Bob French, Fluor BWXT’s environment, safety, health and quality director, said NIOSH was invited to Portsmouth in 2013 by both the company and the United Steelworkers union.

Last month’s report brought no surprises because NIOSH kept Fluor BWXT officials apprised during its two-year inquiry. As NIOSH would raise safety issues, the company would correct them, French said.

“There’s nothing we want more than to assure the safety of our workers,” he said. Building 326 is targeted for demolition in June 2017.

Energy Department spokeswoman Joshunda Sanders wrote in an email that the agency “considers worker health and safety to be a top priority, and we take all recommendations to improve safety seriously. This [NIOSH] letter is being reviewed in that context.”

Jeff Walburn, a former security guard at Portsmouth, said he found the NIOSH report disconcerting.

On the morning of July 26, 1994, Walburn was working in the L-Cage – a storage area for contaminated liquid waste – in Building 326. The plant, then still in production, was operated by Lockheed Martin.

The atmosphere suddenly changed, Walburn said, and he became agitated. Another guard was in the same area.  “It was like we were being stung by bees all over,” Walburn said. His lungs were burned. His hair fell out in clumps. He wound up in the emergency room and spent 11 days in the hospital and two months recovering after that.

Walburn blamed his injury on HF exposure. NIOSH’s findings suggest that similar risks remain for decommissioning workers, he said.

“There are thousands of miles of pipe and pockets of gas trapped within those thousands of miles of pipe,” said Walburn, who brought an unsuccessful lawsuit against Lockheed Martin. “The 326 [building] is a catastrophe waiting to happen.”

In a written statement to the Center last month, Lockheed Martin said it had investigated worker allegations of safety lapses and “could not substantiate” them.