Fibre News


Did risk reduction backfire in space?

Is there a connection between the explosion of the Challenger space shuttle that occurred 11 years ago and U.S. government restrictions on the use of asbestos? In an article published in The Washington Times in January 1996, former U.S. Geological Survey research scientist, Malcolm Ross, re-examines that tragic event and suggests that an impending ban on asbestos use by the EPA may have precipitated it.

As is well known, the explosion was blamed on a breach in the joints of the booster rocket's exterior casing, allowing hot gases to burn the protective O-rings. The agent used to seal the joints in the first nine successful shuttle missions was an asbestos-containing putty. Ross argues that "in the wake of the developing notoriety of asbestos-bearing products and the fear of lawsuits," NASA's supplier of this special putty stopped manufacturing it. A substitute, which contained less asbestos, was used for the Challenger launch. The substitute product did not have the same insulating properties as the putty and it failed to protect the O-rings. Ross concludes by stating that the Challenger disaster reminds us "that measures aimed at lessening risk can actually increase risk, even create risk."



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Rockwell issues a non-asbestos fibres warning

In response to health and safety concerns associated with non-asbestos fibres, Rockwell International, a manufacturer of products containing non-asbestos fibres, issued a technical bulletin in 1995 in which it recommends certain procedures to reduce exposure to these fibres. Rockwell recognizes that non-asbestos fibres are "a cancer and lung disease hazard" and has summarized the risk connected with such fibres as follows:

"Most recently manufactured brake linings do not contain asbestos fibers. These brake linings may contain one or more of a variety of ingredients, including glass fibers, mineral wool, aramid fibers, ceramic fibers and silica that can present health risks if inhaled. Scientists disagree on the extent of the risks from exposure to these substances. Nonetheless, exposure to silica dust can cause silicosis, a non-cancerous lung disease. Silicosis gradually reduces lung capacity and efficiency and can result in serious breathing difficulty. Some medical experts believe other types of non-asbestos fibers, when inhaled, can cause similar diseases of the lung. In addition, silica dust and ceramic fiber dust are known to the State of California to cause lung cancer. U.S. and international agencies have also determined that dust from mineral wool, ceramic fibers and silica are potential causes of cancer."

Recommended work practices
In consideration of the hazards associated with non-asbestos dust, Rockwell advises workers "to use caution to avoid creating and breathing dust when servicing brakes" and provides a list of recommended work practices to achieve this goal. The list consists of the following: the separation of work areas for servicing brakes to reduce risks to unprotected persons; adherence to the allowable exposure levels for non-asbestos fibres; specific procedures for servicing brakes, including the use of pressure enclosures, HEPA vacuums and filters, worker arm sleeves, and wetting techniques; general guidelines for cleaning work areas and for worker clean-up; and the application of proper waste disposal procedures.

Finally, Rockwell recommends that manufacturers of products containing non-asbestos fibres seek further regulatory guidance from such governmental agencies as OSHA and EPA.



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European Trade Union report on carcinogenicity of MMMF

The classification and labeling of MMMF (Man-Made Mineral Fibres) has been on the agenda of the European Union for several years now. In this context, in March 1995, the European Trade Union Technical Bureau for Health and Safety in conjunction with the Vlaamse Instelling voor Technologisch Onderzoek (Belgium) presented a brief to the European Commission Working Group on the Classification and Labeling of Dangerous Substances. The report concludes that the results of human epidemiological studies, studies in experimental animals and tests on availability suggest that all respirable MMMF are "potentially carcinogenic to humans."

Given that there is sufficient scientific evidence that respirable MMMF are carcinogenic and that respirability is a precondition for bio-availability, the briefing considered that the current EU classification structure be modified to allow for an accurate distinction between respirable and non-respirable materials.



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U.S. Department of Labor launches silica education campaign

A national public education campaign highlighting efforts to protect workers from exposure to crystalline silica was officially launched by the U.S. Department of Labor (DOL) on October 31, 1996. The Secretary of Labor, Robert Reich, announced the start of the campaign titled, If It's Silica, It's Not Just Dust at a press conference in Washington, DC. Reich said the campaign is designed to prevent silicosis, a debilitating lung disease.

Reich, referring to a recent preliminary National Institute for Occupational Safety and Health (NIOSH) study detailing worker exposure to silica in seven states, said that there were 230 new cases of silicosis discovered during a one-year period in 1993. "Even though this disease is 100% preventable, these recent studies suggest that the battle against silicosis has not yet been won," Reich added.

An information package produced in conjunction with NIOSH and the American Lung Association includes tips on how to prevent silicosis through dust monitoring, workplace engineering controls, and education and training programs. The package is now available through NIOSH and will also be distributed by DOL inspectors on visits to mines, construction sites, and other affected industries.

The U.S. Occupational Safety and Health Administration (OSHA) supports the DOL initiative. OSHA began a special emphasis progam on silicosis in the summer of 1996 that includes an outreach and enforcement component. OSHA will continue to develop additional protective standards and penalize employers that expose workers to silica hazards.



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An occupational exposure limit for para-aramid fibres

In 1995, the Health and Safety Executive (HSE) in the United Kingdom published a criteria document in which it made a recommendation for an occupational exposure limit for para-aramid respirable fibres used in heat and fire resistant clothing, bullet-proof vests, industrial fabrics, friction products, high strength ropes and cables and high performance composites for sporting goods, aerospace and military use.

The HSE's review of the existing data on the exposure, measurement, and toxic effects of para-aramid fibres led it to propose a health-based occupation exposure limit of 0.5 f/ml, based on an 8-hour time-weighted average.

Health effects studies
 Given the paucity of scientific data on the effects of para-aramid fibres on human health, the HSE focused on animal studies involving rats to determine the material's health effects. Experimental data collected under short-term exposure conditions suggest that "aramid fibres produced a more rapid onset and slightly more marked degree of pulmonary inflammation than chrysotile." However, retained para-aramid fibres were found to be less durable than chrysotile and produced less mesothelial cell proliferation.

No comparable data exist to determine the effects of para-aramid fibres in the lungs of humans exposed to the material. According to the report, the only available human studies indicate that para-aramid's physical abrasion properties may produce slight skin irritation.


Minty C A, Meldrum M, Phillips A M & Ogden T L, p-Aramid respirable fibres: Criteria document for an occupational exposure limit. Health and Safety Executive, 1995.



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This old house

An article in the home renovation magazine This Old House reported the results of studies conducted in the 1980s in the U.S., Canada, and several European nations which showed that the incidence of cancer among fibreglass industry workers was higher than in the general population. Many scientists found these results difficult to interpret because of the presence of other variables, leading the North American Insulation Manufacturers Association to dismiss the findings as inconclusive.

In light of the suspected health hazard associated with fibreglass insulation, the article in This Old House suggests various ways to reduce risk, including the use of respirators for installers and ensuring that the material not be disturbed so as to avoid releasing fibres into the ambient air.



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Keeping warm and staying healthy

In September 1996, the Natural Resources Defense Council, a U.S.-based non-profit environmental membership organization, published a report titled Keeping Warm and Staying Healthy in which it compared the documented environmental attributes, costs, health risks, and effectiveness of fibreglass, cellulose, and cotton insulation. The report noted that, of the three materials, "the most substantial and well documented public health threats are associated with fiberglass." It adds that fibreglass has been classified as a "probable human carcinogen" by "domestic and international health agencies, and is also an eye and respiratory irritant."

The North American Insulation Manufacturers Association has continued to dismiss scientific claims of the carcinogenicity of fibreglass, arguing that the fibres dissolve relatively quickly in the human body. Both sides of this debate await the findings of the current animal studies on fibreglass inhalation conducted in Switzerland. Results are expected in early 1998.



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Biopersistence of cellulose

Durability, a phenomenon related to the biopersistence of inhaled particles inside lung tissues, is believed to be an important parameter in determining the pathogenicity of inhaled solid materials. In a recent study conducted at Germany's Fraunhofer Institute, durability of cellulose fibres in the rat lung was examined. Chemically pure hardwood cellulose fibres and the commercial product Isofloc were tested across a range of fibre dimensions. The researchers found that one year after treatment (instillation), both types of cellulose fibre remained present in the lungs of the test animals.

The hardwood fibres remained unchanged to a large extent; the calculated half-life of fibre clearance is in the range of 1000 days. For the commercial product, Isofloc, fibre splitting made it difficult to calculate a half-life, however calculated on the basis of fibre mass, the researchers estimated a half-life of 72 days.

Muhle H. & Bellmann B. Examinations of cellulose fibre durability in the rat lung, Fraunhofer Institute for Toxicology and Aerosol Research, 1995.



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Research Notes

Asbestos exposure, asbestosis and asbestos-attributable lung cancer

The issue of whether asbestosis is a necessary precursor to asbestos-related lung cancer has been a hotly debated issue in the scientific literature, fueled by important implications for regulations, workers' compensation and litigation. To help shed some new light on this topic, researchers from Tulane University (USA) conducted an extensive review of the animal and human epidemiological evidence. They wrote:

"While the issue of whether asbestosis is a necessary precursor to asbestos-attributable lung cancer cannot at this time be considered settled, the weight of the available evidence strongly supports this proposition... The linkage between inflammation/fibrosis and carcinogenesis is plausible in light of recent work on these fundamental biological processes. There is also ample evidence that diffuse lung fibrosis of other causes, known and unknown, is associated with an excess risk of lung cancer. With the present knowledge regarding this probable linkage, for compensation and other decisions in cases where asbestos attributability of lung cancer is the issue, it is reasonable for judgements of attributability to rest on the presence of asbestosis, diagnosed by either radiography or histopathology."

Jones R, Hughes J & Weill H (1996). Asbestos exposure, asbestosis and asbestos-attributable lung cancer, Thorax, 51:S9-S15.



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Asbestos concentrations following the Kobe earthquake

Following the earthquake that shook the city of Kobe, Japan and its surroundings in January 1995, the media in that country reported that the level of asbestos dust concentration in the stricken areas constituted a health hazard for residents. Tests conducted by the Environmental Agency of Japan showed that the media's reports were groundless.

For a period of six months immediately following the earthquake, the Agency monitored the atmospheric environment for asbestos dust concentration in seventeen separate locations in the disaster area. Their measurements revealed concentrations of asbestos dust that are not considered hazardous to human health. The mean concentrations over the six-month period decreased from a high of 0.0012 f/cc in the second month to 0.0007 f/cc in the sixth month. The maximum measurement obtained in the study was 0.0049 f/cc, coming in the month following the earthquake.

This concern over ambient asbestos concentrations recalls similar worries following the earthquake in the San Francisco Bay area in October 1989. A study by industrial hygienists at the time had also found that asbestos levels had not risen significantly as a result of the damage caused to buildings in the earthquake.



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New evidence links polio vaccine to mesothelioma

According to recent media reports, a monkey virus that contaminated millions of doses of polio vaccine has been directly implicated in triggering mesothelioma. The virus, Simian Virus 40 (SV40), which scientists have found in several types of tumour, including mesothelioma, destroys a key-defence mechanism by switching off a protein that protects cells against cancerous changes.

Epidemiologists have estimated that between 10 and 30 million people in the U.S. alone have received the vaccines containing live SV40. The vaccine was also used extensively in Canada, Europe and Russia. Scientists believe that SV40 may be one of the factors that explains why a significant proportion of mesothelioma cases have no history of asbestos exposure. In addition to evidence that SV40 may play a direct role in causing mesothelioma, some researchers believe that it may be a factor in the unexplained increase in brain cancers.

Sources:
€ Polio vaccine linked to cancer, New Scientist, U.K., 24 August 1996€ New York Magazine, November 21, 1996
€ Tumours linked to '50s polio vaccine, The Globe & Mail, January 31, 1997
€ Monkey Virus DNA found in rare human cancers, Science, Vol. 275, 7 February 1997
€ Carbone, M. Association of Simian Virus 40 with rodent and human mesotheliomas. DNA Tumor Viruses: Oncogenic Mechanisms, ed. Giuseppe Barbanti-Brodano et al., Plenum Press, New York, 1995.



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