The Role of Data in Assessing the Potential Hazards of Man-Made Vitreous Fibers

The North American Insulation Manufacturers Association (“NAIMA”) occasionally gets questions about the health and safety of fiber glass and mineral wool insulation products.  To answer those questions, NAIMA is launching a new blog series.  Our first post is on the use of data in assessing possible fiber hazards.

Fiber glass and mineral wool insulation consists of man-made vitreous fibers and are safe to manufacture, fabricate, install, and use when certain common-sense work practices are followed. These products are the most thoroughly researched insulation material on the market today.

The public health record of fiber glass and mineral wool insulation is based on an extensive body of fiber research validated by such authorities as the International Agency for Research on Cancer (“IARC”), the U.S. National Toxicology Program (“NTP”), California’s Office of Environmental Health Hazard Assessment (“OEHHA”), Health Canada, the U.S. Agency for Toxic Substances and Disease Registry (“ATSDR”), and the U.S. National Academy of Sciences.

NAIMA discusses four types of data that are generated by studies on the fibers that make up fiber glass and mineral wool insulation.  What follows is a short summary of these data types:

1. Human Epidemiology Data – Data from humans – called epidemiology – is the most important information to assess potential hazards. In this area of data analysis, researchers locate fiber glass and mineral wool manufacturing workers who have passed away and review their death certificates for cause of death.  These workers have had long term exposure to the fibers and binders that make up insulation products.  The researchers then compare the health profile of these exposed workers to an unexposed population and determine if the workers have a higher rate of respiratory system cancers or disease.

For example, the leading study for American fiber glass workers covered exposure from   1945-1990 and included nearly a million worker-years of total exposure.  Studies from Europe and Canada provided similar data.  Governmental health agencies have relied on these epidemiology studies to conclude that there is no causal association between fiber exposure and cancer or non-malignant pulmonary disease.

2. Exposure Data – People are constantly exposed to a multitude of environmental agents in the air they breathe, the liquids they drink, the food they eat, the surfaces they touch, and the products they use. This data measures how much exposure to fiber glass and mineral wool insulation fibers occurs during manufacture, fabrication, installation, and end use.  The level of exposure is a significant factor in determining risk.  The authoritative bodies reviewing fiber glass and mineral wool insulation fiber exposure data have concluded that exposures were low because exposure testing was consistently below recommended Permissible Exposure Limits.

3. Animal Bioassay Data – During the late 1980s and early 1990s, new techniques and methodologies were developed to allow realistic inhalation exposure of test animals to carefully sized mineral wool insulation fibers at thousands of times higher levels than in manufacturing facilities.  These new studies became known as the Gold Standard for bioassays of fibers, and the data generated from these studies revealed that exposure to commercially-available fiber glass and mineral wool fibers used in insulation resulted in no increase in tumors in the test animals.  This science was critical to the decision of the world’s authoritative scientific bodies to remove fiber glass and mineral wool from lists of substances previously considered possible carcinogens.

4. Dissolution Rate – A key finding from the 1990s animal studies was that the hazard of a fiber is largely based on how long that fiber stays in the lung after inhalation. Tests allow us to estimate how quickly fibers can dissolve in the lung – the higher the dissolution constant, the more biosoluble the fiber. 

Despite this conclusion from authoritative sources, a recent private study suggests that mineral wool fibers coated with binders are more durable than the fibers successfully tested in animals.  This contradicts numerous previous studies that found no effect of binders.  The many deficiencies in that private study are detailed in a letter to the journal editor that NAIMA submitted in March 2018.  That letter can be found here.

Scientific studies are all about data.  In the case of fiber glass and mineral wool, decades of research have generated a truly substantial amount of robust data used for authoritative scientific bodies to conclude that there is no causal association between exposure to fiber glass and mineral wool insulation and cancer or non-malignant pulmonary disease.  For more information on the health and safety legacy of fiber glass and mineral wool insulation, please visit our website.    

BIBLIOGRAPHY

Government of Canada, Priority Substances List Assessment Report – Mineral Fibres (Man-Made Vitreous Fibres), 1993.

“Historical Cohort Study of US Man-Made Vitreous Fiber Production Workers,” Journal of Occupational and Environmental Medicine, September 2001, Vol. 43, No. 9.

International Agency for Research on Cancer, Press Release, October 24, 2001 (http://www.iarc.fr/en/media-centre/pr/2001/pr137.html).

International Agency for Research on Cancer, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Man-Made Vitreous Fibres, Vol. 81 (Lyon, France: WHO/IARC, 2002).

National Institute of Environmental Health Sciences, National Toxicology Program, Fact Sheet, The Report on Carcinogens, June 2011 (http://www.niehs.nih.gov/about/materials/roc12fs.pdf).

National Research Council, Subcommittee on Manufactured Vitreous Fibers, National Academy of Sciences, Review of the U.S. Navy’s Exposure Standard for Manufactured Vitreous Fibers, National Academy Press, 2000.

U.S. Department of Health and Human Services, Public Health Services, Agency for Toxic Substances and Disease Registry, Toxicological Profile for Synthetic Vitreous Fibers, September 2004, pp. 1-11, 13.

U.S. Department of Health and Human Services, Public Health Services, National Toxicology Program, Report on Carcinogens, Twelfth Edition, 2011 (http://ntp.niehs.nih.gov/ntp/roc/twelfth /roc12.pdf).