The good news is that the workers tested do not appear to be at higher risk for the blood cancers leukemia or lymphoma. The bad news is that, for reasons that are not fully understood, they do appear to have a higher chance of getting malignant pleural mesothelioma or ovarian cancer.
The NIOSH team in Cincinnati examined the causes of death through 2008 of 5,203 workers at two boatbuilding plants in Washington state. The workers had all been exposed to styrene, fiberglass, and wood dust between 1959 and 1978. Styrene is a chemical used to produce a number of reinforced plastic boat parts. Fiberglass is plastic that is reinforced with the addition of glass fibers.
Although mesothelioma, an aggressive malignancy of the membranes that surround internal organs, is usually caused by exposure to asbestos, researchers were surprised to find excess mesothelioma deaths among the boat builders. There was no evidence that the workers had been exposed to asbestos at either of the plants, but the scientists had other theories about the unexpected rates of mesothelioma and ovarian cancer.
“Unanticipated excess mesothelioma and ovarian cancer mortality…could be due to fiberglass exposure or employment elsewhere, or could be chance findings,” writes lead author Avima Ruder, PhD, a NIOSH Senior Research Epidemiologist, in the journal Occupational and Environmental Medicine.
The production and handling of fiberglass can produce fibrous glass dust that is considered by the National Toxicology Program to be “reasonably anticipated as a human carcinogen” if it is inadvertently inhaled, although it has not been directly linked with mesothelioma. The shape of asbestos fibers is believed to trigger mesothelioma by lodging permanently in lung tissue and causing long-term irritation and inflammation.
Scientists at the University of Minnesota trying to determine the mesothelioma risk among workers in the state’s iron mines faced a similar dilemma as the NIOSH team. Although their long-term study of taconite workers did expose a higher rate of mesothelioma, the jury is still out as to whether the excess cases were caused by exposure to elements in the iron mines, or to asbestos encountered on other jobs or even in their homes.
Before the public became aware of its link to mesothelioma in the 1960’s, asbestos was widely used in a range of commercial and home building products. This naturally-occurring mineral in still present in and around closed mines and in thousands of older homes and buildings.
Ruder, A et al, “Cancer Mortality among Styrene and Fibreglass Exposed Workers in the Reinforced Plastic Boatbuilding Industry”, June 2014, Occupational and Environmental Medicine, Suppl. 1:A74-5.