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Safety of Rock and Slag Wool Insulation

Rock and slag wool fall within a group of materials historically referred to as man-made vitreous fibers, now known as synthetic vitreous fibers (SVFs) - reflecting the glassy, non-crystalline nature of these materials. The mineral wool form of SVF was developed in the mid-1800s by melting slag and spinning it into insulation. Rock wool is made from natural minerals like basalt or diabase. Slag wool is made primarily from iron ore blast furnace slag.

Rock and slag wool insulation products play a significant energy-savings role by reducing energy use in homes, office buildings, businesses and manufacturing plants. In addition to providing thermal insulation, rock and slag wools absorb sound and, with a vapor retarder, help control condensation. Because they are non-combustible and have melting temperatures in excess of 2,000 degrees Fahrenheit, they are also used to prevent the spread of fire. Rock and slag wools will not support the growth of mildew, mold or bacteria, when tested in accordance with the specifications of the American Society for Testing and Materials (ASTM C 665).

The primary uses of rock and slag wool are for acoustical ceiling tile; residential, commercial and industrial insulation; and spray-on fireproofing. The excellent thermal resistance of these materials is a major factor in their use as residential and commercial insulation, pipe and process insulation, insulation for ships, mobile homes, and domestic cooking appliances, and a wide variety of other applications.


Play it Smart, Play it Safe - DVD (English/Spanish)

This worker training tool is a 15-minute DVD designed to provide important information in a fun and entertaining way to contractors and workers who handle fiber glass, rock and slag wool (synthetic vitreous fiber) insulation products.

 

FAQs About Rock and Slag Wool Insulation

In a press release announcing the updated report IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 81, Man-Made Vitreous Fibres, the International Agency for Research on Cancer (IARC) stated that:

"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 of 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." IARC further stated that "the more commonly used vitreous fibre wools including insulation glass wool, rock (stone) wool and slag wool are now considered not classifiable as to carcinogenicity to humans (Group 3)."

For more information about the IARC decision, click here.


What does the research show about the health and safety of rock and slag wool?

The health aspects and safe use of mineral wools have been examined for nearly 70 years. NAIMA and its member companies have invested tens of millions of dollars in research projects - with leading independent laboratories and universities in the United States and abroad - to investigate the possible human health effects of rock and slag wool as well as other synthetic vitreous fibers (SVFs), such as fiber glass.

Industry studies, as well as studies by governments and others, have examined the following:

Airborne levels of rock and slag wool fibers during their manufacture, installation and use;

The health of more than 13,000 current and former workers engaged in the manufacture of rock and slag wool in the United States and Europe; and

The effects of rock and slag wool on laboratory animals.

Findings from all types of studies have been consistent. Airborne levels of respirable rock and slag wool fibers have been demonstrated to be very low, less than one fiber per cubic centimeter of air (1 f/cc) in most instances. Studies among workers have demonstrated no consistent association between lung cancer or non-malignant respiratory disease and occupational exposure to rock and slag wool.

For more details on recent scientific studies on the health aspects of rock and slag wool insulation, visit the Research section of this site or visit the NAIMA Literature Library for a complete listing of health and safety literature.

Do rock or slag wools cause cancer in people?

Studies examining possible health effects and safe use of mineral wools have found no consistent association between exposure to rock and slag wool and respiratory disease or cancer in humans. The weight of the scientific evidence confirms that rock and slag wool are safe to manufacture, install and use when manufacturers' recommended work practices are followed. 

Do rock and slag wool fibers contribute to problems with indoor air quality?

Rock and Slag wool fibers actually improve the indoor environment by controlling heat loss or gain while reducing condensation and also providing acoustical insulation. Once rock or slag wool products are installed, no significant fiber release occurs.

The majority of airborne fiber levels in buildings containing one or more rock and/or slag wool products are very low, generally less than 0.001 f/cc. In fact, in 1990 the World Health Organization's Working Group on Indoor Air Quality reviewed all scientific studies and concluded: "Current airborne man-made mineral fiber concentrations in indoor environments are considered to represent an insignificant risk."

See also the related publication - Facts #63: Health and Safety Facts for Rock and slag Wool: PDF |HTML | Order printed copies from Literature Library (N041)

Are there any special handling guidelines for working with rock and slag wool?

If sufficient amounts of rock and slag wool are released into the air during manufacture and handling, some workers may experience temporary upper respiratory irritation. Like skin irritation, upper respiratory irritation is a "mechanical" irritation to the fibers. The irritation will subside once the exposure is discontinued. Some people are more sensitive, some less, some not at all. Manufacturers of rock and slag wool products have recommended a number of safety measures designed to minimize any potential irritation.

Rock and slag wool manufacturers have put together work practices that provide practical safety measures designed to minimize any potential irritation. Click here to see these Work Practices. In all cases, however, manufacturers' specific recommendations as outlined in their Materials Safety Data Sheets (MSDSs) should be consulted.

Where Can I Go For More Information?

For more information on the health and safety of fiber glass and rock and slag wool insulations, click here to find out about NAIMA’s Health and Safety Partnership Program (HSPP). Or, visit NAIMA's Literature Library for a complete list of health and safety publications on this Web site. You may also want to visit our members' Web sites for additional information on fiber glass insulation.

See also the related publication - Facts #63: Health and Safety Facts for Rock and slag Wool: PDF |HTML | Order printed copies from Literature Library (N041)