by Mr. Glyn Jones, M.A.So., P.Eng., CIH, ROH
What is Asbestos?
Asbestos is the term that has been given to a group of naturally occurring mineral fibres. The name asbestos comes from the Greek word meaning indestructible. There are many types of asbestos. The classification of asbestos depends upon the rock types which form the asbestos. The most common types include:
Asbestos was extracted from open pit mines in many countries: Canada, Soviet Union, United States, China, South Africa and Australia. Canada is formerly the world’s largest producer of asbestos.
Chrysotile, amosite and crocidolite are the types of asbestos that have been used most often in the past.
Health Hazards of Asbestos Fibres
The Three Main Diseases Caused by Inhalation of Asbestos Fibres
Lung and Laryngeal Cancer
Mesothelioma
Acceptable Exposure Limits
Special Properties of Asbestos
Asbestos has been called the “magic mineral”. Asbestos has a variety of physical properties which make it very useful:
As a result of its many useful properties, asbestos has been formed into over 3000 different products.
Once released, fibres can remain airborne for several hours, depending on their size and local air movement. Generally, the smaller the fibre, the longer it takes to settle. Because fibres remain airborne unprotected individuals may inhale them. This could result in fibre related disease after prolonged or repeated exposure.
Trapped fibres may cause three main asbestos-related diseases:
Asbestosis
In asbestosis, macrophages turn normal lung tissue into scar tissue (fibrosis) as they try unsuccessfully to digest the asbestos fibres. The lung becomes more rigid as the proportion of scar tissue increases, making it difficult to breathe. Once the fibrosis begins, it cannot be completely stopped even if occupational exposure to airborne asbestos stops. All types of asbestos are capable of producing this fibrosis.
Cancer is basically a group of cells dividing out of control, producing a tumor in the affected tissue, which prevents its normal function.
Somehow asbestos fibres trapped in the lungs can trigger cancerous growth in lung tissue. Although cancer of the respiratory tract has definitely been linked to the inhalation of asbestos fibres, the relationship has not been clearly defined. Asbestos workers who smoke increase their risk of developing lung cancer as much as 90 times, compared to non-smoking, unexposed individuals. Very few people who develop lung cancer live more than 5 years after diagnosis.
Mesothelioma is an extremely rare and fatal disease. It is cancer of the lining of the lung (pleural mesothelioma) or lining of the chest/abdominal wall (peritoneal mesothelioma).
Approximately 85% of those who contract this fatal cancer of the chest and abdominal cavities have been exposed to asbestos. Although asbestos workers have an increased chance of developing mesothelioma, occupational exposure is not necessary. In some rare cases household members of asbestos workers, who have brought asbestos home on their clothes, have contracted the disease.
Acceptable exposure limits are set for 8 hour or 15 minute occupational exposures to asbestos fibres. Higher exposures are permitted for 15 minute periods. Only 4 -15 minute work periods are permitted per work shift. In Alberta these acceptable concentrations are called Occupational Exposure Limits, or OEL’s. These are outlined in Table 3 of Schedule 1, Occupational Exposure Limits for Fibres, of the Chemical Hazards Regulation. The concentrations are expressed in number of fibres per cubic centimeter of air. The Federal allowable limits are termed 8-hour Threshold Limit Values.
| Type of Asbestos | 8-hour OEL (f/cm3) | 15-min OEL (f/cm3) | Federal TLV (f/cm3) |
| amosite | 0.2 | 1 | 0.5 |
| chrysotile | 0.5 | 2.5 | 2 |
| crocidolite | 0.2 | 1 | 0.2 |
| tremolite | 0.2 | 1 | 2 |
Asbestos Control Options
There are four general ways in which to control the release of asbestos fibres:
- ongoing management
- removal
- encapsulation
- enclosure
Four Main Principles of Handling Asbestos
Regardless of the quantity of asbestos material disturbed, four general principles of asbestos handling should be applied each and every time.
- 1. Enclose the Work Area
A simple enclosure prevents the migration of asbestos dusts to surrounding areas. The degree of enclosure depends upon the type of asbestos job performed. Elaborate, well-scaled enclosures are needed for high risk jobs performed inside of buildings. Drop sheeting may be adequate for low and moderate risk jobs. Glove bags may be used to enclose limited pipe sections when removing cold pipe insulation. - 2. Minimize Fibre Release
Inhalation of asbestos fibres presents a serious health risk. The release of airborne asbestos fibres should be minimized. Wherever possible asbestos material should be thoroughly sprayed with water and a wetting agent before it is disturbed. Only asbestos-approved vacuum cleaners may be used to collect asbestos debris or to draw contaminated air away from the source of disturbance. - 3. Protect the Worker
It is impossible to eliminate the release of fibres when disturbing most asbestos materials. Therefore it is important to ensure that anyone within the work area wear the appropriate personal protective equipment: an approved respirator, coveralls and hood, work boots and gloves. Workers should shower as soon as possible after leaving the work area. Other personal protective equipment may also be required; e.g. hardhat, hearing protection. - 4. Ensure Cleanup
An asbestos job is not complete until all equipment and surfaces in the work area have been cleaned of residual asbestos debris. All asbestos-contaminated waste must be discarded in a sealed drum or plastic bag. This includes gross asbestos debris, contaminated plastic sheeting used for enclosures and disposable personal protective equipment.
The above presentation was made by Mr. Glyn P. Jones to the membership of the Building Operators Association (Calgary) during their April 14, 1998 meeting. Mr. Glyn P. Jones is co-founder and principal of Environmental Health Professionals Ltd.; has more than twelve years experience working in Occupational Hygiene; has designed and managed hundreds of asbestos surveys and abatement projects and is frequently invited to lecture in his field and has taught university and college courses in Occupational Hygiene.
For more information Glyn can be reached at (403) 244-3233.
On behalf of the Association I would like to thank Mr. Jones for his extremely informative presentation. Many members obtained new information which will, at one point, be applicable in the proper performance of their job.
The editor
First published May 1998
