Industry-sponsored study backfires:

By Robert Horowitz
Hamsters forced to breathe fine-diameter fiberglass in a Swiss laboratory developed fibrotic lung conditions, tiny tumor-like growths, abnormal mesothelial cells and damaged cell nuclei only six months into a two-year study. One test animal exposed to fiberglass developed mesothelioma, the rare and fatal cancer of the lung lining almost exclusively associated with asbestos. The degree of lung damage observed in test animals exposed to fiberglass was equivalent to that in hamsters exposed to moderate doses of amosite asbestos, according to grading protocols.

Like other rodent-inhalation studies sponsored by the North American Insulation Manufacturers' Association (NAIMA), this effort was intended to show fiberglass products are safe. NAIMA is required to share preliminary results with the US Environmental Protection Agency (EPA) under Section 8(e) of the federal Toxic Substances Control Act, regardless of whether the study turns out as they wish.

"Among the intercurrent deaths, a mesothelioma of the mixed papillary and solid sarcomatous type was noted in one hamster exposed to the test article MMVF 33 (a special purpose glass fiber)," noted Kenneth D. Mentzer, Executive Vice President of NAIMA, in an April 5 letter to the EPA. "This mesothelioma was characterized by multiple, visceral and parietal nodules, consisting of villous to papillary surface on tightly packed multi-layered sarcomatous cells."

MMVF 33 is fine diameter "specialty" fiber produced by the Manville between 1989 and 1995, using the flame-attenuation process. Also tested were ordinary insulation fibers made through the centrifuge process; hamsters exposed to these fibers developed excess macrophage cells, as well as a smaller number of tiny tumor-like growths, known as "microgranulomas," in their lungs. Macrophage cells are the body's defenders; they engulf and consume foreign bodies. When macrophages run into thin but very long bodies, like fiberglass or asbestos, they die attempting to consume the fiber.

NAIMA's switched the study animal from rats to hamsters at the urging of the U.S. Occupational Safety and Health Administration (OSHA). Previous studies indicated hamsters were more sensitive to lung hazards than rats. Subsequent to that finding, NAIMA began using rats exclusively in its inhalation studies, which were then trumpeted in a costly, time-consuming and ultimately vain attempt to prevent the listing of respirable-sized fiberglass as "reasonably anticipated" to cause cancer in the U.S. government's annual (now semi-annual) report on cancer-causing substances. The list, including fiberglass, was published in June, 1994.

If the study results at six months are an indicator, the switch to hamsters will profoundly impact the use of nose-only inhalation studies and the acceptance of fiberglass as an important carcinogen. VOF normally contends inhalation studies are not sensitive enough to detect a cancer risk, and studies in which fiberglass and other synthetic mineral fibers (SMFs) are directly implanted into test animals are preferable. Independent researchers, the German government, and many in OSHA concur with this view. All fiberglass insulation products contain a percentage of fibers in the same size range as MMVF33.

Microgranulomas, tiny tumor-like growths sometimes found inside tumors, were found in nearly all hamsters exposed to glass or asbestos fibers. Although technically not a cancer or even a tumor, microgranulomas could progress into either, according to Will Forrest, a toxicologist with the California Department of Health Services.

"There is a fairly standard progression for many kinds of tumors where they start out non-malignant and turn malignant," said Forrest.

The report also notes the deposition of collagen in the lungs after exposure to fiberglass and asbestos. Collagen is contained in connective tissue and is associated with scarring. Deposition of collagen in the lungs makes the lungs more rigid, said Forrest, decreasing the ability of the tiny air sacs, known as alveoli, to squeeze oxygen out of air and transfer it to the blood.

"Collagen is the material that forms in the tissue that makes it stiff and fibrotic," said Forrest. "Collagen deposition means the deposition of stuff that would tend to produce fibrosis. If you are seeing that, you can figure fibrosis will occur."

Lung fibrosis is known to be caused by exposure to asbestos (asbestosis), silica dust (white lung disease) and even coal dust (black lung disease). An interesting controversy, noted Forrest, is whether fibrosis is even necessary for cancer to appear. The prevailing view, because the two conditions are often found together, is that fibrosis is necessary. Some toxicologists, Forrest included, think it possible to get cancer without fibrosis.

The mesothelium is a thin layer of cells which lines the lungs and other body cavities. Mesothelioma, a cancer of the lung lining, is 100 percent fatal; killing with speed and excruciating pain. Thousands of employees of asbestos producing companies all over the world suffered this death. (Some of these companies now produce fiberglass insulation.)

The report mentions mesothelial hypertrophy in hamsters exposed to fiberglass and asbestos. Hypertrophy literally means overgrowth, said Forrest. Cancer is an extreme form of cellular overgrowth.

"Mesothelial hypertrophy is most likely a precursor for mesothelioma," he said.

Hyperchromatic nuclei and micro-nucleated giant cells are both conditions related to chronic exposure to irritants, according to Jerry Ward, a toxicologist with the National Cancer Institute. Like the conditions discussed above, these symptoms are not cancer, he said; it is rare they turn into cancer.

However, Ward pointed out that when cancer does occur, researchers typically find granulomas, collagen deposition and fibrotic lesions, hyperchromatic and micronucleated cells, and similar conditions in the victim.

A final report on the hamster study was expected in late 1997.  If you know how to locate the final study, please contact us.