Following news that several employees had developed a rare neurological disease, the NASA Ames Research Center is facing a new wave of concern that hazardous substances linked to the nearby Superfund sites could be affecting its workers' health. The recent scare has prompted a new round of testing for toxic chemicals in old buildings at Ames, but health officials say harmful substances have stayed within safety limits.

NASA Ames is situated at Moffett Field on federal property with underground aquifers known to be contaminated with industrial solvents, including TCE, left by the area's former semiconductor factories. While hazardous to human health, the toxic groundwater plume has been viewed as a manageable problem under a regimen of regular testing and cleanup administered by the U.S. Environmental Protection Agency.

But fears persist among NASA employees that low amounts of hazardous chemicals that fall below federal safety thresholds could be behind suspicious diseases affecting co-workers. Federal Occupational Safety and Health Administration officials as well as Ames employees' union representatives are seeking an epidemiological study to determine whether the toxins bear any correlation with at least seven reported cases of ALS, also known as Lou Gehrig's disease.

The new concern over a possible link emerged last year when the federal OSHA officials received two complaints from an anonymous NASA employee alleging that workers housed in an aging building were experiencing sickness from a chemical smell. Following these complaints, a NASA engineer provided his own independent research showing a significant number of workers over the last 15 years had contracted ALS.

It remains a medical mystery as to what causes non-genetic ALS, which accounts for more than 90 percent of cases. The disease is almost always fatal and there's no known cure, but it is extremely rare -- only about two people out of 100,000 per year are affected by it.

The research, which was described to a Voice reporter, indicated that seven employees who worked out of a cluster of buildings on the north side of the Ames campus had contracted ALS since 2000. Six of those employees died from the disease. About 2,500 people work at the Ames campus, making it statistically significant that so many cases of ALS appeared in one group.

The independent research was spearheaded by NASA Space Flight project manager Stevan Spremo, who said he began looking last year for disease patterns after a co-worker in his 50s was diagnosed with ALS. It seemed eerie since it was hardly the first time an Ames colleague was stricken with the disease, he said.

"I noticed this pattern of people getting sick, and no one seemed to be writing down these things," Spremo said. "Is there a problem here? I still don't know if there is, but it didn't look right."

Despite no formal training in medical research, Spremo began working in his spare time to map out where employees who contracted various diseases had worked by using old phone books, newspaper obituaries and word-of-mouth among the workforce.

His survey tracked about 170 people who had contracted either cancer, lupus, Parkinson's disease, and ALS (amyotrophic lateral sclerosis). Most of those diseases were scattered across the campus, but the ALS cases were unique because they were conspicuously packed in a tight section of older buildings dating back to the 1940s.

Spremo shared his research with officials from the union, and the information was eventually disseminated among Ames administrators, health regulators and even the offices of U.S. reps Jackie Speier and Anna Eshoo. The disease map drove many employees to demand more information, said Tom Clausen, vice president of the Ames Federal Employees Union.

"Most people who see this map get concerned," Clausen said, "We have a lot of people who love working at NASA, who love making a significant contribution through the work we do, but they need to know they're working in a safe place."

Clausen declined to share the disease map with the Voice after discussing the request with other union officials.

NASA employees' fears over possible toxic hazards have been heightened over recent years. One flash point for those concerns came when a season of heavy rainfall caused flooding in the basement of the aging Building 241. The basement, formerly used as a print shop and mail room, was reportedly built on a flawed foundation designed with metal sections lodged in between concrete slabs. Decades of corrosion had caused the metal portions to wear away, leaving space for groundwater to begin leaking inside.

At the time, Building 241 was situated about 100 feet outside the boundary for where the toxic groundwater plume was located, meaning the EPA was not testing it for contaminants. NASA eventually closed off the basement of Building 241, yet employees working on the upper levels were concerned that TCE vapors could still be wafting up through the ventilation system, Clausen said. Trichloroethylene, more commonly known as TCE, is considered carcinogenic to humans by all routes of exposure, according to the EPA.

More recently, a 2013 U.S. Department of Defense report found toxic vapor levels exceeding EPA limits inside several occupied buildings at Moffett Federal Airfield, including the NASA Ames convention center and the flight systems research lab. Around the same time, parents who worked at Moffett Field voiced concerns that a children's day care center located off R.T. Jones Road could be exposed to soil contaminants from a nearby U.S. Army construction project that was digging up dirt along the contaminated Superfund plume.

Employees' concerns that harmful vapors could somehow be permeating into their workspaces are often tied to the age of the Ames facilities. The site reportedly has a $500 million backlog of deferred maintenance projects, much of it for old infrastructure that dates back to World War II.

Clausen explained that NASA employees paid close attention in 2013 as Google workers went public with complaints about similar toxic vapors discovered in a cluster of relatively new Whisman neighborhood offices. For many NASA workers fresh out of college, it was the first time they had learned about the Superfund pollution that stretched across the area, he said.

"When employees here at Ames heard about what's happening at Google a mile away, they're curious: 'Is the air in my workspace safe too?'" Clausen said. "It's one thing to go into a dangerous place for a few minutes; it's another to be working in a low concentration for years."

Some employees developed their own ways of coping with the potential hazards. One office worker mounted carbon filters everywhere in her office to leach any volatile chemicals out of the air. Bottled water is generally favored in lieu of tap water.

In an interview with the Voice, one longtime Ames researcher described how a first-floor lab in Building 240 where she routinely worked would immediately give her a sore throat and a sharp migraine. The feeling was like "night and day" when she entered the room, and other employees described similar symptoms, she said. The Voice agreed to withhold her name over concern for her job security.

As a scientist, she said she realizes the data doesn't support the toxic plume being the source, but it's something she finds hard to dismiss. She is content now that she works on the other side of the campus, but if she was relocated back to that building, she said she would probably quit.

"Something is wrong there," she said. "I don't know if the groundwater plume is it, but it fits the profile."

Based on the mounting concerns, NASA administrators on Oct. 19 held a first-ever town hall meeting to address issues surrounding the Superfund site. The room was packed with a standing-room only crowd of about 120 people. A panel of officials from NASA, EPA and OSHA gave assurances that employees' health and safety was a paramount priority.

OSHA Industrial Hygienist Amber Rose said her agency received an anonymous complaint in November 2015 alleging that workers in Building 241 were getting sick from groundwater vapors as well as mold and algae. Her agency partnered with EPA officials to install a series of air-sampling canisters around the building. While a few chemicals in the air were detected, they were well below hazard levels and were considered "insignificant," Rose said.

A few months later, a second complaint to OSHA was made, warning that employees in buildings 241 and 240 were suffering from chemical vapors, particularly in the early morning. Rose said she returned to the Ames campus in July to install a set of charcoal tubes designed to test for five different hazardous chemicals.

"All of my results came back with nothing detected," she told the audience. "At this time, we haven't uncovered any hazard to make us believe there's any issues related to the groundwater."

The OSHA inspection team did issue a hazard alert letter to NASA regarding black gunk that would sometimes fall from the air ducts in older buildings, according to employees. A mass-spectrometer analysis showed the substance was some kind of acetate, but Rose said it wasn't likely to be harmful unless employees were exposed to a large amounts.

Rose admitted the failure to detect any prominent chemicals probably did little to mollify any NASA employees fretting about subtle environmental hazards. In partnership with the Ames employees' union, she recently requested that a division of the U.S. Centers for Disease Control and Prevention conduct an epidemiological study that would look into the ALS patterns uncovered by Spremo. The CDC division ultimately declined the request.

In an email to the Voice, a CDC spokesman said that an epidemiological study would be difficult due to the challenges of verifying diagnoses, potential environmental factors and the background history of ALS cases. The CDC's ALS registry has only been active since 2010 and it has not conducted any previous studies on clustered ALS cases.

OSHA and union officials say they intend to continue seeking a medical professional or perhaps a graduate student to pursue a disease study at Ames.

NASA administrators at the meeting emphasized they were committed to safety and they urged employees to immediately bring any concerns to their attention.

"Ames clearly is committed to maintaining the health and well-being of its employees and partners," Ames director Eugene Tu said in a statement to the Voice. "NASA will continue to monitor conditions and will continue to conduct sampling and studies. Ames will share results with employees, the employee union, tenants and with the relevant agencies."