Why Some Products Have a Cancer Warning Label

Apr 11, 2019 9:55:28 AM By Stacy Fitzgerald-Redd
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Epidemiology-smallWhy Some Products Have Cancer Warning Labels

Have you ever wondered why certain products have a cancer warning label on them and others do not? Well, you’re not alone. Here’s why:

The Occupational Safety and Health Administration’s (“OSHA”) Hazard Communication Standard[1] requires by law that chemical manufacturers classify the hazards of their chemical substances.  Manufacturers must identify and consider the full range of available scientific literature and other evidence concerning the potential hazards.[2]  Although there is no requirement to test the substance to determine how to classify its hazards, many manufacturers do perform such tests.[3] Employers then must communicate those hazards to employees in labels, Safety Data Sheets, and by other effective means.

Substances that present a cancer hazard must feature a label noting that hazard. Manufacturers are required to identify and consider the full range of available scientific literature and other evidence concerning potential cancer hazards.  In addition, if one of several authoritative scientific bodies has determined that a substance has a possible or known cancer hazard, that determination is recognized by OSHA and the cancer hazard must be noted and communicated.[4] 

The authoritative scientific bodies recognized by OSHA include the following:

  • S. National Toxicology Program (“NTP”), Annual Report on Carcinogens;
  • International Agency for Research on Cancer (“IARC”), Monographs; and
  • OSHA itself where OSHA has determined that a substance is to be regulated as a carcinogen.

California’s Proposition 65 is not on OSHA’s list of authoritative scientific bodies.  But, Proposition 65 has its own requirements to label products that fit certain criteria.

So, if IARC or NTP have determined that a substance poses a potential cancer hazard, the substance or product will require a cancer warning label. If a product doesn’t carry a cancer warning label, it may be because it has never been tested for carcinogens.  Untested doesn’t’ mean a product is safe; it means it’s untested.

Fiber glass products were at one time listed by IARC, NTP and Proposition 65 in California as possible carcinogens and for a number of years, these products contained cancer warning labels.   Mineral wool products were only listed as a possible carcinogen by IARC. Neither fiber glass nor mineral wool products carry these labels today.

After extensive testing and research, in October 2001, an international expert review by IARC re-evaluated the 1988 IARC assessment of glass fibers and removed glass, rock and slag wool fibers from its list of substances that are “possibly carcinogenic to humans.”[5]  All fiber glass and rock and slag wools that are commonly used for thermal and acoustical insulation are now considered not classifiable as to carcinogenicity to humans (Group 3).  In 2001 IARC noted specifically:

Epidemiologic studies published during the 15 years since the previous IARC Monographs review of these fibres in 1988 provide no evidence of increased risks of lung cancer or mesothelioma (cancer of the lining of the body cavities) from occupational exposures during manufacture of these materials, and inadequate evidence overall of any cancer risk.[6]

IARC based this decision on new and better research and test data on fiber glass hazard, which were generated at great expense by the fiber glass and mineral wool industry.  IARC also retained its Group 3 classification for continuous glass filaments used for composite reinforcement purposes and the Group 2B “possible carcinogen” classification for certain special purpose glass fibers not used for insulation purposes.

In June 2011, the U.S. NTP removed from the Report on Carcinogens (“RoC”) biosoluble glass wool fibers used in home and building insulation.[7]  NTP stated that “not all glass wool fibers cause cancer.”[8]  In fact, the vast majority of glass fibers manufactured in the United States are not considered even possible carcinogens by NTP. 

Also, in 2011, California’s Office of Environmental Health Hazard Assessment (“OEHHA”) published a modification to its Proposition 65 listing to include only “Glass Wool Fibers (inhalable and biopersistent).[9]  Fiber glass fibers used in building insulation are not included on the Proposition 65 list.

The action taken by IARC, NTP, and OEHHA removes all legal requirements – Federal or California – for a cancer warning label on packages of the biosoluble fiber glass used in today’s fiber glass insulation.

The NTP and IARC decisions are consistent with the conclusions reached by Health Canada in 1993,[10] the Agency for Toxic Substances and Disease Registry (“ATSDR”) in 2004,[11] and the U.S. National Academy of Sciences, which in 2000 found “no significant association between fiber exposure and lung cancer or nonmalignant respiratory disease in the MVF [man-made vitreous fiber] manufacturing environment.”[12]  These findings are further supported by one of the most comprehensive epidemiological studies ever created.[13]

So, today’s fiber glass and mineral wool insulation products do not need a cancer warning label.  This is because the fiber glass and mineral wool industry conducted extensive research and testing to confirm that these products present no possible cancer hazard and that research and those tests were recognized by two important authoritative bodies – IARC and NTP.


[1] 29 C.F.R. 1910.1200.

[2] 29 C.F.R. 1910.122(d)(2).

[3] Id.

[4] 29 C.F.R. 1900. 1200. See Appendix A and D.

[5] 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).

[6] IARC Press Release, 24 October 2001 (http://www.iarc.fr/en/media-centre/pr/2001/pr137.html).

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

[8] 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).

[9] Biosoluble glass wool fibers dissolve more rapidly in body fluids than other fibers that have been associated with human disease.

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

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

[12] NRC Subcommittee on Manufactured Vitreous Fibers. 2000. Review of the U.S. Navy’s Exposure Standard for Manufactured Vitreous Fibers. National Academy of Sciences, National Research Council, Washington, D.C.: National Academy Press.

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



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