Vermiculite -
Health, Safety and Environmental Aspects
Vermiculite and Health Aspects Associated with Potential Contaminants
Crystalline Silica
Control Measures and Personal Protective Equipment
Vermiculite is Not Asbestos
Review of: Sampling and Analysis of Consumer Garden Products That Contain Vermiculite (EPA 744-R-00-010, August, 2000)
Statement by The Vermiculite Association on the Recently Released Government Studies of Vermiculite and the Potential Asbestos Exposure (May 2005)
Introduction to Vermiculite and Environmental Aspects
Vermiculite is a member of the phyllosilicate mineral group and is micaceous in nature. It is found in many parts of the world but only a limited number of sources are worked as commercial deposits. The vermiculite is mined and refined using a variety of techniques and supplied commercially in a range of particle size grades of vermiculite concentrate (unexpanded).
Vermiculite is most commonly used in its exfoliated (expanded) form. The exfoliated vermiculite is lightweight (low bulk density), absorbent, non-combustible, and an excellent insulator that has proven useful in many environmentally beneficial and public safety related applications including:
1. Fire protection to improve the safety of commercial and residential construction.
2. Fire rated door assemblies and wallboards (both gypsum and vermiculite based).
3. Growing media and soil amendments for fruits, vegetables, and many flowers.
4. Insulating media in home construction that reduces energy consumption and costs.
5. Lightweight concrete to improve insulation and increase noise absorption.
6. Animal feedstuffs to preserve integrity of feed and promote the health of livestock.
7. Bio-remediation aid to clean contaminated soils and sites.
8. Packaging aid for the safe transport of many kinds of materials, including spill containment of liquids.
Other forms of vermiculite include finely ground and liquid dispersions, each of which utilize vermiculite's high aspect ratio platelets to produce unique end use applications.
Providing the vermiculite is used and handled in accordance with the suppliers' recommendations, it can be used in a safe and environmentally friendly way. As with all other materials it is important to adopt normal good working practices and to comply with local and national regulatory requirements. Requirements do vary on a country by country basis and it is advisable that local agencies be contacted regarding specific requirements.
The following notes are intended to provide guidance on some particular aspects relevant to health, safety, and environmental matters. Additional data on specific products may be available from producers.
- - - - - - - - Top of page - - - - - - - -
Vermiculite and Health Aspects Associated with Potential Contaminants
Vermiculite is a naturally occurring, mica-type mineral that has been used beneficially in numerous industrial applications since the late 1940's. It has been demonstrated as being safe to use, and no serious health risks have been found resulting from exposure to vermiculite.
Vermiculite and other ore bodies can contain a variety of associated minerals such as mica, quartz, feldspar, etc. The associated minerals are unique to a particular deposit and, in some cases, may include minerals which could pose a health risk if present in significant quantities. In most countries, manufacturers are required to publish and make available Material Safety Data Sheets (MSDS). These sheets will typically identify any hazards associated with the material and also provide information on safe handling and proper disposal.
Asbestos fibres are a potential risk to health, and in the past there has been some vermiculites contaminated with trace amounts of asbestiform material. Vermiculite ore bodies currently in use by the major producers, do not pose a health risk when used in accordance with the manufacturer's MSDS. However, there are numerous sources of commercial vermiculite available in the world today and it is important for the end user to understand test data from a particular manufacturer.
Such testing should take into account both mineralogical and morphological differences between asbestos and non-asbestos varieties of the same amphibole or serpentine mineral.
Finally, it is important to note that the issue of potential for fibrous asbestos contamination exists for a wide range of naturally occurring materials. Included in this list are materials such as sand, clay, and gypsum. Due to this, and other studies referencing background levels of asbestos in the environment, it is inappropriate to state that any naturally occurring material is asbestos free. Any reference to trace asbestos levels must include (as a minimum): analysis technique, detection limit, and definition of asbestos used in the study.
- - - - - - - - Top of page - - - - - - - -
Crystalline Silica
Vermiculite, in ore concentrate and exfoliated state, may contain small quantities of crystalline silica, as quartz. This is usually only present as non-respirable particles but mechanical action such as milling may reduce any quartz that may be present to a respirable particle size.
Silica is a very abundant material in a variety of forms and accounts for approximately 20% of the earth's crust with 95% being quartz. It is present in nearly all mining operations, and as an extremely common mineral has been the subject of many detailed studies, summarized in the Crystalline Silica Primer published by the US Bureau of Mines.
Trace amounts of free silica are often found in silicate minerals while materials such as sand and gravel consist mainly of free silica.
It has been known for centuries that prolonged and excessive exposure to high concentrations of respirable free silica in dust can cause a related lung disease of occupational origin, silicosis. This is a non-cancerous, but extremely serious lung disease. Recent attention has focused on a relationship between silica and lung cancer. Confounding factors in human studies and flaws in animal studies have not given rise to conclusive evidence, however the International Agency for Research on Cancer (IARC) have now classified crystalline silica as a carcinogen.
Some countries will even require any material containing more than 0.1% crystalline silica to be labelled as a carcinogen.
- - - - - - - - Top of page - - - - - - - -
Control Measures and Personal Protective Equipment
Like all materials, vermiculite can be subject to control measures with regard to its handling, use in processing, transportation, end use and possible disposal. Since local and national requirements vary from country to country it is not possible to deal with them individually in this brief note, and users should check for any statutory requirements.
As with numerous finely divided particulate materials, inert or nuisance dust may be released during handling of vermiculite. Other commercially important materials with similar dusting characteristics include sugar, grain, cement, and sand. Symptoms associated with inhalation exposure to airborne dust may include coughing, sneezing, and minor upper respiratory irritation. Inhalation over long periods of substantial amounts of any inert dust can overload the lung clearance mechanism, making the lungs more vulnerable to respiratory disease. Skin and eye contact may also cause minor physical or mechanical irritation.
It is important that dust control measures be instituted to ensure that airborne dust levels are kept below regulatory limits if they exist. In general dust concentrations of above 10mg/m³ total inhalable and 5mg/m³ respirable are considered a risk to health. While these levels could be reached in commercial operations they are unlikely to exist in domestic use.
In the United States, the Occupational Safety and Health Administration (OSHA), has established a Permissible Exposure Limit (PEL) which is the maximum amount of airborne crystalline silica that an employee may be exposed to during a working shift. Other countries may have similar limits.
Dust control measures should be used in preference to Personal Protective Equipment (PPE) where ever possible. If control measures can not be instituted the following PPE is recommended;
1. dust respirator to protect against inhalation exposure.
2. safety glasses with side shields or safety goggles to prevent mechanical or physical eye irritation.
It should be noted that most suppliers regard the use of PPE as part of good hygiene practice regardless of regulatory exposure limits.
Our brochure, "Vermiculite - Health, Safety and Environmental Aspects", is available as a pdf format file from our Papers section.
- - - - - - - - Top of page - - - - - - - -
Vermiculite is Not Asbestos
There are no real causes for concern about health risks from vermiculite: a review of the mineralogy of vermiculite and its fundamental differences to asbestos explains why.
Summary
Vermiculite is a sheet silicate mineral that is found as flaky crystals; it is not a fibrous mineral like asbestos. Fibres of vermiculite can be formed by breakage of the flakes or by curling of the edges of the flakes. Such mineral fibres do not constitute asbestos, and fibrous shape does not, by itself, mean that they will behave like asbestos.
Vermiculite dusts, including these fibrous fragment forms, have demonstrated very few if any health effects, other than those that could be expected from any low toxicity silicate. Unlike asbestos, vermiculite has shown very few ill-effects in experimental testing with animals. Chemical testing suggests that it may not stay long enough in the lung to do serious damage.
All vermiculite ores contain a range of other minerals that were formed along with the vermiculite in the rock. Vermiculite ores from some sources were even found to contain asbestos minerals but asbestos is not intrinsic to vermiculite and only a few ore bodies have been found to contain more than tiny trace amounts. Nevertheless serious public concern was generated because of the known occurrences of asbestos in vermiculite deposits such as those in Montana that were closed some years ago.
Asbestos is the name given to a number of naturally occurring fibrous silicate minerals that have been exploited for their useful properties such as thermal insulation, chemical and thermal stability, and high tensile strength. Chrysotile, known as white asbestos and a member of the Serpentine mineral group is the commonest having been used widely in asbestos cements, laggings and textiles. It is also becoming recognised as the least harmful of the asbestos fibres because of its lower chemical stability.
The amphibole minerals form a very large group with a wide range of chemical compositions united by a common crystal structure. The normal forms for all of the amphiboles are prismatic, blocky, or rodlike crystals. However, certain of the amphiboles, for example grunerite (amosite), riebeckite (crocidolite), tremolite, actinolite and anthophyllite may occasionally occur in asbestos forms although these are rare in comparison to the normal varieties.
Some confusion has arisen over the definition of amphibole asbestos which has led to the wrong impression that both forms of the amphiboles are the same and equally hazardous. It is now recognised that the prismatic mineral forms and the asbestos forms, even of the same amphibole, are mineralogically distinct, fracture in critically different ways, and the dusts formed by breakage have different effects on health. While asbestos dusts are carcinogenic in animals and humans, the prismatic amphibole dusts are very much less potent, and probably harmless to humans.
No asbestos related diseases have been found among the workers in any of the vermiculite deposits except those in Montana where the asbestos exposure was known to be very high. Where the possible health effects from industrial exposure to prismatic amphiboles have been examined they have been mostly insignificant or ambiguous at worst.
A wide range of regulations in Europe and the USA cover the supply, packaging and labelling of materials containing asbestos or other carcinogens, and their use in the workplace. All are relevant to the vermiculite producers, manufacturers and suppliers, who are required to provide health and safety data sheets. While the legislation trigger levels for all asbestos types are currently 0.1% of the bulk material and few vermiculite deposits would fail to meet this standard, recent research shows that a target level of no more than 0.001% for amphibole asbestos would be preferable for the vermiculite industry.
Analytical techniques using optical and electron microscopy are available or are being developed now to identify and to quantify asbestos in mineral raw materials and products. Detection limits are below the suggested target levels so that it is possible to screen new and established supplies of vermiculite for their suitability.
The paper, from which the above summary is taken, "Vermiculite is not Asbestos" by John Addison, is available as a pdf format file from our Papers section.
- - - - - - - - Top of page - - - - - - - -
Review of: Sampling and Analysis of Consumer Garden Products That Contain Vermiculite (EPA 744-R-00-010, August, 2000)
Conclusions
With the exception of experiments performed using samples of Zonolite from Libby. Montana, the results of these EPA studies provide no scientific basis for the statement that currently available vermiculite products contain asbestos, or that use of these products present measurable cancer risks
In the interpretation of the analytical data, EPA ignored its own published definition of asbestos, mis-identified fibers, and applied risk factors that are not valid for the non-asbestiform fibers found in the vermiculite products studied. The conclusions reached by EPA on the basis of their studies are not supported by their data.
The review, from which the above conclusions are taken, "Review of: Sampling and Analysis of Consumer Garden Products That Contain Vermiculite (EPA 744-R-00-010, August, 2000)" by Dr. Eric Chatfield, is available as a pdf format file from our Papers section.
- - - - - - - - Top of page - - - - - - - -
Statement by The Vermiculite Association on the Recently Released Government Studies of Vermiculite and the Potential Asbestos Exposure (May 2005)
Summary
In December 2004, the National Institute for Occupational Safety and Health (NIOSH), Division of Respiratory Disease Studies, Field Studies Branch, released 10 site studies measuring asbestos exposure during the handling and expansion of vermiculite and the use of vermiculite horticulture products. Study sites were selected to include the types of vermiculite currently in use today. The concern about vermiculite and asbestos grew out of asbestos problems at the W.R. Grace Libby, Montana mine. The Libby deposit contained a unique type of vermiculite, which had asbestos as a co-mineral. This W.R. Grace Libby, Montana mine closed in 1990.
Among the 10 sites studied were three greenhouses using a broad range of commercial vermi-culite growing mixes. The results of these NIOSH studies show that the use of commercial vermiculite horticulture products presents no significant asbestos exposure risk to commercial greenhouse or home horticulture users.
The full statement, from which the above summary is taken, "Statement by The Vermiculite Association on the Recently Released Government Studies of Vermiculite and the Potential Asbestos Exposure (May 2005)" is available as a pdf format file from our Papers section.
- - - - - - - - Top of page - - - - - - - -
