Workers exposed to radiation and toxic chemicals during decades of nuclear research and rocket engine testing at Rocketdyne's Santa Susana Field Laboratory did not experience a statistically significant increase in cancer deaths, according to a new study released Friday.
But nuclear activists and a scientist who participated in an earlier UCLA health study that found elevated cancer risks among past Rocketdyne workers criticized the findings of the four-year study, which was commissioned by Boeing, Rocketdyne's parent company, and the United Aerospace Workers union. The review cost $3.5 million.
"This is like the tobacco industry hiring people to claim smoking isn't dangerous for you," said Daniel Hirsch, president of the anti-nuclear group Committee to Bridge the Gap. "I don't believe any thinking person will believe Boeing's self-serving study for a minute."
Researchers found that overall cancer deaths among 46,970 workers employed at Rocketdyne's Santa Susana Field Lab and Canoga Park facilities for at least six months between 1949 and 1999 were lower than in the general population. In fact, the study concluded, "no cause of death was significantly elevated," even among those exposed to radiation and toxic chemicals.
The study looked at medical records, radiation exposure records and death certificates. It did not physically examine any current or retired workers and did not attempt to calculate the number of Rocketdyne employees who may have gotten cancer but survived.
The report stated that verifiable data on 99.2% of all workers was collected, and that a precise cause of death was determined for 97.6% of the 11,118 workers who had died.
Of those, 3,189 of the deaths were attributed to cancer, and of those workers, 655 were primarily employed at the Santa Susana lab and 456 were classified as "radiation workers." Lung cancer claimed 1,068 of the total, but researchers said that data on smoking and diet as possible contributing factors were unavailable.
John Boice, scientific director for the Maryland-based International Epidemiology Institute, the private firm that conducted the research, said his study expanded on the earlier UCLA studies because it included four additional years of data and 198 additional cancer deaths.
The institute's study also accounted for occupational doses of radiation and chemical exposure by the nearly 28% of employees who worked somewhere other than Rocketdyne at some point in their careers.
"The study found no consistent evidence that working at the lab adversely affected worker health," Boice said.
But the study also pointed out that although the number of Rocketdyne workers exposed to high doses of radiation -- greater than 5,000 millirems, or roughly the equivalent of 833 chest X-rays -- during their careers was small, those workers were nearly three times as likely to die from leukemia. In addition, it found that those exposed to chemicals such as hydrazine and trichloroethylene, used in rocket fuel and solvents, had a greater chance of getting lung cancer and kidney cancer.
Boice said that only two workers at the Santa Susana lab were found to have died of kidney cancer, twice the number that would be expected in the general population but too small a number to verify as anything more than chance. "Those numbers are not reliable because they are so small," he said.
Dr. Beate Ritz, the principal UCLA epidemiologist on the earlier studies, funded by the U.S. Department of Energy, challenged Boice's conclusions. She said the potential cancer risk for workers exposed to high levels of radiation and chemical exposure should not be dismissed.
"You don't want to expose another 1,000 workers to hydrazine before you feel it's conclusive enough to say, 'We should be more careful,' " Ritz said.
One major weakness of the new study is that it doesn't track those workers who may have gotten cancer from radiation and chemical exposure but survived, Ritz said.
As for the distinctly different conclusions of the two studies, Ritz said, "When you pay people $3.5 million to produce something ... it's easy to get another interpretation of the same data."
By comparison, the UCLA study reviewed the records of all individuals employed by Rocketdyne and predecessor North American Aviation from 1949 through 1994. That included 4,563 workers exposed to external radiation.
The five-year study concluded that "all available evidence ... indicates that occupational exposure to ionizing radiation among nuclear workers at Rocketdyne has increased the risk of dying from cancers of the blood and lymph system."
The study found nine more cancer deaths than the expected 91 among workers exposed to high levels of radiation from external sources.
And it found 15 more than the expected 40 among those who received any internal radiation exposure. That group included primarily people exposed to dust and shavings when they machined uranium to make fuel elements.