Fine Mineral Fibers

Hazard Summary-Created in April 1992; Revised in January 2000

Fine mineral fibers include glasswool, rockwool, slagwool, glass filaments, and ceramic fibers. There is no information available on the acute (short-term) effects of fine mineral fibers in humans. Glasswool, rockwool, and slagwool administered by inhalation produced little pulmonary fibrosis in animals. Two epidemiological studies did not show a relationship between occupational exposure to glass mineral fibers and adverse clinical signs or mortality. Studies in humans have shown mixed results regarding exposure to glasswool, glass filaments, rockwool, and slagwool and an increase in cancer. Animal studies have not shown an increase in lung or respiratory tract tumors from exposure to glasswool, rockwool, or slagwool by inhalation, while animal studies have shown mixed results from exposure to ceramic fibers. The International Agency for Research on Cancer (IARC) has classified glasswool, rockwool, slagwool, and ceramic fibers as Group 2B, possibly carcinogenic to humans, and glass filaments as Group 3, not classifiable as to their carcinogenicity to humans.

Please Note: The main sources of information for this fact sheet are IARC's Monograph on the Evaluation of the Carcinogenic Risk of Chemicals to Man: Man-Made Mineral Fibres and the State of California's Toxic Air Contaminant List Summary on Fine Mineral Fibers.

Uses

Most glasswool, rockwool, and slagwool is used for thermal and acoustical insulation in the construction industry. (2)
Glass filaments are used mainly as textiles and as reinforcement materials in plastics. (2)
Ceramic fibers are being produced in increasingly large amounts for high-temperature insulation and in specialty products; they are a significant replacement for asbestos. (2)

Sources and Potential Exposure

Emissions of fine mineral fibers have been reported in industries including crude petroleum and natural gas extraction, manufacture of aircraft and parts, and electrical services industries. (1)
Fine mineral fibers are generally not used in home, commercial, and industrial insulation products used in the U.S. (1)
The primary route of human exposure to fine mineral fibers is by inhalation, mainly during their manufacture, formulation, and use. (2)

Assessing Personal Exposure

No information is available on assessing personal exposure to fine mineral fibers.

Health Hazard Information

Acute Effects:

There is no information available on the acute effects of fine mineral fibers in humans.
Glasswool, rockwool, and slagwool administered by inhalation produced little pulmonary fibrosis in animals. (2)

Chronic Effects (Noncancer):

Two epidemiological studies have shown no relationship between occupational exposure to glass mineral fibers and adverse clinical signs or mortality, although the prevalence of small opacities in the lungs of exposed workers was increased in one study. (1)
EPA has not established a Reference Concentration (RfC) or a Reference Dose (RfD) for fine mineral fibers.

Reproductive/Developmental Effects:

No studies are available regarding the reproductive or developmental effects of fine mineral fibers in humans or animals.

Cancer Risk:

Glasswool:

A study of glasswool workers in the U.S. showed a slight increase in mortality from respiratory cancer, however, this increase was not statistically significant. (2)

A European study showed no overall excess mortality from lung cancer related to glasswool exposure in humans. (2)

A study of Canadian glasswool workers showed a substantially increased mortality from lung cancer, which was statistically significant, but was not related to time since first exposure or to duration of exposure. (2)

In inhalation studies in rats, there was no significant increase in lung tumors from exposure to glasswool, however a few respiratory tract tumors occurred. (2)

EPA has not classified glasswool for carcinogenicity.

IARC has classified glasswool as Group 2B, possibly carcinogenic to humans. (2)

Glass filaments:

There was no increase in respiratory cancer among glass filament workers in the U.S. and no increase in lung cancer in the European workers. (2)

No statistically increase in tumor incidence were seen in experiments in which glass filaments of relatively large diameter (>3 µm) were administered intraperitoneally to rats. (2)

EPA has not classified glass filaments for carcinogenicity.

IARC has classified glass filaments as Group 3, not classifiable as to their carcinogenicity to humans. (2)

Rockwool and Slagwool:

A study of rockwool/slagwool workers in the U.S. indicated a statistically significant increase in mortality from respiratory cancer. (2)

In a study of European workers, there was an overall, statistically nonsignificant increase in lung cancer among rockwool/slagwool workers. (2)

In two studies in which rats were exposed to rockwool by inhalation, no statistically significant increase in lung tumor incidence was seen. (2)

In an inhalation study of slagwool in rats and hamsters, no increase in the incidence of respiratory tract tumors was reported. (2)

EPA has not classified rockwool or slagwool for carcinogenicity.

IARC has classified rockwool and slagwool as Group 2B, possible carcinogenic to humans. (2)

Ceramic fibers:

A statistically significant increase in lung tumors were seen in rats exposed to ceramic fibers by inhalation. (2)

Two additional studies showed no increased tumor incidence in rats and hamsters exposed to ceramic fibers by inhalation. (2)

EPA has not classified ceramic fibers for carcinogenicity.

IARC has classified ceramic fibers as Group 2B, possible carcinogenic to humans. (2)

Physical Properties

Fine mineral fibers include mineral fiber emissions from facilities manufacturing glass, rock, or slag fibers (or other mineral derived fibers) of average diameter 1 micrometer (µm) or less. (1)
Glasswool is the major type of fiber found in manufacturing facilities using fibers less than 1 µm. (1)
Rockwool, slagwool, glass filaments,and ceramic fibers are other types of fine mineral fibers. (2)
Fine mineral fibers have high tensile strength, dimensional stability, high heat resistance, resistance to chemical attack and flame resistance. (1)
They are composed mainly of borosilicate, but can also contain other mineral oxides. (1)
Most ceramic fibers are white to cream in color and tend to be polycrystallines or polycrystalline metal oxides. (3)

Health Data from Inhalation Exposure

ACGIH TLV--American Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.
NIOSH REL--NIOSH's recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.
OSHA PEL--Occupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

The health and regulatory values cited in this factsheet were obtained in December 1999.
^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.
^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice. OSHA numbers are regulatory, whereas NIOSH and ACGIH numbers are advisory.
^c PEL for general industry: inert or nuisance dust, shipyard (fibrous glass, mineral wool): total dust.
^d PEL for general industry: inert or nuisance dust, shipyard (fibrous glass, mineral wool): respirable fraction.
^e TLV for continuous filament glass fibers, fibers longer than 5 µm.
^fREL for fibrous glass dust: total dust.

References

California Environmental Protection Agency. Toxic Air Contaminant Identification List Summary for Fine Mineral Fibers. ARB/SSB/SES, Berkeley, CA. 1997.
International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man: Man-Made Mineral Fibres. Volume 43. World Health Organization, Lyon. 1988.
National Toxicology Program. U.S. Department of Health and Human Services, Public Health Service. 8th Report on Carcinogens. National Institute of Environmental Health Sciences. Research Triangle Park, NC. 1998.
Occupational Safety and Health Administration (OSHA). Occupational Safety and Health Standards, Toxic and Hazardous Substances. Code of Federal Regulations. 29 CFR 1910.1000. 1998.
American Conference of Governmental Industrial Hygienists (ACGIH). 1999 TLVs and BEIs. Threshold Limit Values for Chemical Substances and Physical Agents. Biological Exposure Indices. Cincinnati, OH. 1999.
National Institute for Occupational Safety and Health (NIOSH). Pocket Guide to Chemical Hazards. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention. Cincinnati, OH. 1997.