Slag wool or mineral wool insulation health effects & asbestos content.

This slag wool insulation article series illustrates and describes mineral wool or "rock wool" and slag wool insulation materials and addresses questions of health effects of exposure to slag wool or slag wool dust and debris.

Page top photo: under the stereo-microscope we can easily see the shiny black spheres that are characteristic of slag wool based mineral fiber insulation. Where these are present we consider this detail a positive confirmation of the material's identity.

Slag Used in Rock Wool / Mineral Wool Insulation Products: Health Effects?

What is Slag Wool Insulation?

Slag wool is a manmade vitreous fiber made by spinning slag into insulating fibers. Some rockwool producers use nearly pure recycled steel slag. But typically slag-wool insulation uses a mix of about 70% slag (blast furnace waste) and 30% rock or stone wool fibres.

"Mineral wool" is a generic term that can also encompass rock wool, stone wool (a synonym), or slag wool.

For most purposes, mineral wool, stone wool, slag wool, and rock wool are synonyms, though some of these terms such as "rockwool" may be trademarked by some companies.

But these products are not quite identical, and even among manufacturers who are using recycled blast furnace waste (slag), the percentages of composition vary across manufacturers and possibly even across production run.

Mineral wool insulation, developed in the 1850's, patented in 1875 in the U.S. and this material, also called rock wool or in some texts slag wool insulation remained in popular use in the U.S. up to the 1950's, and is still in use today (2008) in some new construction, in manufactured housing, and in special applications such as the insulation of low-slope roofed cathedral ceilings and scissors-truss roofs.

Benefits of using Slag to Make Insulation: opinion from a slag recycler.

[The following is a reader's OPINION about the benefits of producing insulation from slag waste, followed by our reply. - Ed.]

Anonymous (a slag recycler) said:

Are there any companies that produce slag based insulation in the USA? I can't believe this country. Here is a recycled product that from everything I have read is fire proof, better r-value, and doesn't make you itch like fiberglass but we won't make it.

Why? Are there no business minded people left in this country? You would think even the tree huggers and the government would think a recycled,fireproof insulation would meet there approval.

I recycle slag and can't understand why I am having such a hard time selling a recycled product even after I take out all the metals,screen and produce a quality product that even passes penn dot specks.

It compacts better,in most cases is harder and you didn't have to rape mother earth to get it. Not forgetting the stone quarries can still make concrete with there stone so we won't have to import other countries concrete.

What's that worth?

Less going into landfills,less imports, less holes dug in mother earth and better, safer insulation. the fuel savings not having to ship insulation and concrete across oceans and dig unnecessary holes should pay for the fuel needed to make the rock wool insulation.

I don't know but I think we could use the jobs here and maybe export a product ourselves. What a concept. No one cleans the air from smokestacks like the USA and last I looked there isn't a wall to stop the smoke between here and China, so lets get real. Please tell me your opinion and let me know if anyone knows of a company that is or might be interested in producing slag wool in the USA.

Reply: Research on health effects of production or use of mineral wool / slag wool products

Slag products are still in active discussion regarding their use in insulating products both in the U.S. and in other countries as you can read at

• Al-Homoud, Mohammad S. "Performance characteristics and practical applications of common building thermal insulation materials." Building and environment 40, no. 3 (2005): 353-366.

Depending on the actual slab you are suggesting be used to produce insulation (which certainly has been done elsewhere). These references shed some light on present and previous health effects of exposure to slag or mineral wool or "rockwool" particles and fibers.

• Boffetta, Paolo, Rodolfo Saracci, Aage Andersen, Pier A. Bertazzi, Jenny Chang-Claude, John Cherrie, Gilles Ferro et al. "Cancer mortality among man-made vitreous fiber production workers." Epidemiology (1997): 259-268.
• Cherrie, J., S. Krantz, T. Schneider, I. Öhberg, O. Kamstrup, and W. Linander. "An experimental simulation of an early rock wool/slag wool production process." Annals of Occupational Hygiene 31, no. 4B (1987): 583-593.
  Abstract:
  
  This paper presents the results from an experimental simulation of a rock wool production process with conditions similar to those operating in the 1940s. Data are presented to illustrate the reduction in airborne fibre levels when oil was added to the product and the effect of workers handling batches of insulation material.
  
  Addition of oil to the product resulted in a reduction in the airborne fibre levels from 3 to 9 times in different situations. The time-weighted average concentration during the period of the experimental production work was approximately 1.5 Fr ml−1 with oil added and approximately 5 Fr ml−1 without oil.
  
  The handling of MMMF in a small enclosed cabin gave rather higher levels, approximately twice those measured in the production experiment. The exposures while handling blocks of insulation (intended to simulate discontinuously produced material) compared with continuously produced material were not substantially different.
  
  External factors which could influence the fibre levels were monitored. These data are discussed in relation to a mathematical model of past exposure presented by DODGSON et al. [Ann. occup. Hyg. 31, 567–582 (1987)] at this symposium.
• Consonni, Dario, Paolo Boffetta, Gilles Ferro, Rodolfo Saracci, Aage Andersen, Jenny Chang-Claude, John W. Cherrie et al. "Lung cancer mortality among European rock/slag wool workers: exposure-response analysis." Cancer Causes & Control 9, no. 4 (1998): 411-416.
  Abstract:
  
  Objectives: The purpose was to analyze the relationship between semi-quantitative indices of exposure to man-made vitreous fibers and lung cancer mortality among European rock/slag wool (RSW) workers.
  
  Methods: The study population comprised 9,603 male workers employed in RSW production in seven factories in Denmark, Norway, Sweden, and Germany, followed up for mortality as of 1990-91. Estimates of past exposure to respirable fibers were used to calculate cumulative exposure with a 15-year lag and maximum annual exposure based on employment history up to 1977.
  
  Rate ratios were estimated via multivariate Poisson regression, adjusting for country, age, calendar year, time since first employment, and employment status.
  
  Results: A total of 159 lung cancer deaths were included in the analysis of which 97 among workers with more than one year of employment.
  
  We found nonstatistically significant trends in lung cancer risk according to cumulative exposure. Relative risks (RR) in the four quartiles were 1.0 (reference), 1.3 (95 percent confidence interval [CI]=0.8-2.4), 1.2 (CI=0.7-2.1), and 1.5 (CI=0.7-3.0, P test for trend=0.4).
  
  When workers with less than one year of employment were excluded, there was no increased risk; the RRs in the four quartiles were 1.0, 0.9 (CI=0.4-2.0), 0.8 (CI=0.3-1.9), and 1.0 (CI=0.4-2.7). No trend was present according to maximum annual exposure. The results were not consistent among countries.
  Conclusions:
  
  We found a positive association between exposure to respirable fibers and lung cancer mortality. However, the lack of statistical significance, the dependence of the results on inclusion of short-term workers, the lack of consistency among countries, and the possible correlation between exposure to respirable fibers and to other agents reduce the weight of such evidence.
• Kim, K-A., W. K. Lee, J. K. Kim, M-S. Seo, Y. Lim, K-H. Lee, G. Chae, S-H. Lee, and Y. Chung. "Mechanism of refractory ceramic fiber-and rock wool-induced cytotoxicity in alveolar macrophages." International archives of occupational and environmental health 74, no. 1 (2000): 9-15.
  Abstract:
  
  Objectives: Man-made vitreous fibers (MMVFs) can induce cytotoxicity in a way similar to that of other particles, including silica and asbestos fibers. However, as yet the mechanism of MMVF-induced cytotoxicity is still not clear.
  
  This report aims to clarify the mechanism of MMVF-induced cytotoxicity in the alveolar macrophage (AM). In this mechanism, an attempt to prove the involvement of the adenosine triphosphate (ATP) generation system and the polyinosinic acid-inhibitable scavenger receptors was made.
  
  Methods: Several parameters were observed for cytotoxicity, such as cell viability, the release of lactic dehydrogenase (LDH) and ATP levels in rat AM's that were treated with refractory ceramic fibers (RF2) and rock wool (RW1).
  
  A specially designed ATP generation system was used to determine the effect of MMVF on ATP generation. A scavenger receptor ligand was applied to evaluate the relationship between scavenger receptors and MMVF-induced ATP depletion.
  
  Results: A 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay indicated that both RF2 and RW1 caused a decrease in cell viability and this decrease was concentration-dependent.
  
  RF2 and RW1 increased the release of LDH with increasing fiber concentration. From these parameters, RF2 was shown to exhibit greater cytotoxicity than did RW1. Both fibers decreased the intracellular ATP content and this decrease was concentration-dependent. The decrease was more pronounced in RW1 than in RF2 at all fiber concentrations.
  
  These fibers suppressed succinate-triggered oxygen consumption. Polyinosinic acid, a ligand of the scavenger receptor, inhibited the MMVF-induced decrease in ATP concentration.
  
  Conclusion: These results suggest that RF2 and RW1 can induce cytotoxicity and ATP depletion in the AM through the polyinosinic acid-inhibitable scavenger receptor. ATP depletion was the important factor in MMVF cytotoxicity, especially by RW1.
• McConnell, E. E., O. Kamstrup, R. Musselman, T. W. Hesterberg, J. Chevalier, W. C. Miiller, and P. Thevenaz. "Chronic inhalation study of size-separated rock and slag wool insulation fibers in Fischer 344/N rats." Inhalation toxicology 6, no. 6 (1994): 571-614.
• Somlai, J., V. Jobbágy, Cs Németh, Z. Gorjánácz, N. Kávási, and T. Kovács. "Radiation dose from coal slag used as building material in the Transdanubian region of Hungary." Radiation protection dosimetry 118, no. 1 (2006): 82-87.
• Somlai, J., Cs Németh, Z. Lendvai, and R. Bodnár. "Dose contribution from school buildings containing coal slag insulation with elevated concentrations of natural radionuclides." Journal of radioanalytical and nuclear chemistry 218, no. 1 (1997): 61-63.
• In the U.S. slag was used in insulation products such as described in this patent
  "Insulation." U.S. Patent 2,330,941, issued October 5, 1943.
• Back in 1932 this patent disclosure described paper insulation using both slag and asbestos
  Weber, Louis. "Insulating paper." U.S. Patent 1,887,726, issued November 15, 1932.
  "Per cent Slag wool fibre 80 Asbestos fibre, 15 Colloidal clay L 5 In making the paper, the fore oing ingredients are mixed together. Sn clent water is added to the mixture to form a slush"
• Also see research on mineral wool, rock wool, or rockwool atReferences or Citations

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: Some mineral wool insulation is falling into my bedroom from a small hole. Is this harmful?

I recently had a carpenter in my older home (built 1981) fixing an issue in the attic and much to my disappointment made a hole in the attic and all of this (i'm guessing rockwool insulation) came tumbling down in my master bedroom covering everything.

Some of the things it landed on are non washable. Is this insulation harmful to me and my family's health???? Please respond ASAP major clean up in the process. - Geniah Melendez

Moderator Reply: Generally not in small amounts; It depends ...

Rockwool is a mineral fiber product, and of course it could contain dust from the attic: insects, debris, etc. If you HEPA vacuum up the dust and launder what can be laundered or dry cleaned you should be OK. It's not radioactive and it's not asbestos. Heroic measures should not be needed.

Reader comment from Debra Monte:

You should be more concerned with dust from the walls and ceilings, which most likely contained lead paint. Get your blood work done and get tested for lead content in your blood. The likelihood of asbestos in home insulation is very low.

However, there may have been a combination of insulation types, such as rock wool/mineral and vermiculite. Vermiculite that was mined in Libby, Montana does contain a small amount of asbestos.

Moderator Follow-up:

Debra
At the article titled VERMICULITE INSULATION you will find US EPA and other authoritative sources that help separate opinion from fact about asbestos and other environmental hazards.

I agree that lead hazards are ubiquitous in older homes in many areas and are an important concern. We have published extensive information about lead hazards in buildings and in water supplies, found through our page top and page bottom major topical link ENVIRONMENT

Watch out: also be sure to read ASBESTOS IN MINERAL WOOL / STONE WOOL in this article series.

Question: does modern rock wool still contain formaldehyde?

9/11/154 Darlene said:

Does today's rock wool still have formaldehyde? I have what appears to be rock wool insulation in an add-on room of my old farm house, but it has a paper like on the outside and a foil like material on the inside. We have the walls open and want to insulate, but are unsure as what to do.

Do we slash the foil and add more rock wool or tear out what we have and start fresh. We just want to do the right thing and tired of all the seconds guesses at the big box stores.

Reply:

Darlene

Rock wool is a mineral fiber inslulation material that does not now and never did include formaldehyde.

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Continue reading at MINERAL WOOL by MICROSCOPE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• ASBESTOS INSULATION
• ASBESTOS-FREE INSULATION MATERIALS
• BALSAM WOOL BATT INSULATION - a cellulose product, not a mineral fiber
• INSULATION R-VALUES & PROPERTIES - home
• MINERAL WOOL - ROCK WOOL INSULATION - home
  • MINERAL WOOL / ROCK WOOL DEFINITIONS
  • MINERAL WOOL / "Rock Wool" COMPOSITION
  • MINERAL WOOL / STONE WOOL ASBESTOS CONTENT
  • MINERAL WOOL APPEARANCE VARIATIONS
  • MINERAL / SLAG WOOL AIRBORNE PARTICLES
  • MINERAL / ROCK WOOL INSTALLATION, SETTLING
  • MINERAL WOOL / STONE WOOL R-VALUES
  • MINERAL or SLAG WOOL HEALTH EFFECTS
  • MINERAL WOOL by MICROSCOPE
  • SPINTEX MINERAL WOOL PROPERTIES - MANSVILLE

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MINERAL or SLAG WOOL HEALTH EFFECTS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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Citations & References

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