Release Of Asbestos Fibers Research Articles

On the release of asbestos fibers from weathered and corroded asbestos cement products

The controversy on whether weathered and corroded asbestos cement products are emitting biologically significant asbestos fiber concentrations in ambient air has not been resolved. Nor is it known if the weathered and corroded asbestos cement products release asbestos fibers which have the same carcinogenic potency as "standard" chrysotile. The purpose of this research project was to develop a method for sampling and measuring asbestos fiber emissions from solid planar surfaces (i.e., roofs and facades) consisting of asbestos cement products and to develop methods for studying the physical and chemical changes and the carcinogenic potency of the emitted fibers. Using this method asbestos fiber emissions in ambient air have been measured in the FRG during 1984/1986. The emissions of asbestos fibers longer than 5 microns were in the range 10(6) to 10(8) fibers/m2.hr. The ambient air concentrations of these asbestos fibers were for the most part less than 10(3) fibers/m3. It was shown that the emitted asbestos fibers were chemically changed and it was shown with animal experiments that their carcinogenic potency did not differ from the carcinogenicity of "standard" chrysotile fibers.

The release of asbestos fibers from vinyl-asbestos floor tiles

There have been extensive studies of the release of asbestos fibers from friable materials used for construction. To date very little is known about the release of asbestos fibers from materials we assume to be non-friable. Since one of the major uses of asbestos was in the manufacture of floor tiles, and flooring is scoured prior to applying sealants, we have studied the release of asbestos from tiles treated in ways which model the processes tiles would be subjected to over their time of use.Vinyl-asbestos tiles were gathered and assayed for their asbestos content by TEM and polarized light microscopy (PLM). Containments were set up and the following experiments performed: 1. 9 inch square tiles were drilled 10 times with a 3/4 inch drill 2. tiles were drilled once with the drill bit above 3. tiles were boken into 1 1/2 inch pieces 4. tiles were broken into 4 pieces 5. tiles were stripped, and then coated with sealants prior to further scrubbing.

Non-Occupational Exposure to Asbestos in Buildings: A Practical Risk Management Program

Current federal regulations do not address non-occupational exposure to asbestos. In the absence of such regulations, if asbestos-containing materials are present in a building, it is advisable to develop a management program to ensure that the inhalation risk to building occupants does not increase with time and that appropriate steps are taken during activities which have the potential to release asbestos fibers to air. When numerous areas of a building contain asbestos, priorities must be established for selecting and implementing appropriate surveillance or interventions for control. We present a framework for implementing an Asbestos Risk Management Program, the primary objective of which is to minimize the risk of employee and public exposure to asbestos in air. The program includes a decision framework for evaluating and ranking building areas according to the asbestos fiber release potential, and assigns priorities for control interventions. Another decision framework is presented for selecting an...

Non-Occupational Exposure to Asbestos in Buildings: A Practical Risk Management Program

Current federal regulations do not address non-occupational exposure to asbestos. In the absence of such regulations, if asbestos-containing materials are present in a building, it is advisable to develop a management program to ensure that the inhalation risk to building occupants does not increase with time and that appropriate steps are taken during activities which have the potential to release asbestos fibers to air. When numerous areas of a building contain asbestos, priorities must be established for selecting and implementing appropriate surveillance or interventions for control. We present a framework for implementing an Asbestos Risk Management Program, the primary objective of which is to minimize the risk of employee and public exposure to asbestos in air. The program includes a decision framework for evaluating and ranking building areas according to the asbestos fiber release potential, and assigns priorities for control interventions. Another decision framework is presented for selecting an air monitoring strategy and for making appropriate decisions based upon measured airborne fiber concentrations. Procedures are included for minimizing employee exposure, operating a maintenance permit system and maintaining an episode response plan. Procedures for employee education and training, medical surveillance programs, asbestos monitoring and record-keeping also are presented.

Engineering and Operating Approaches for Controlling Asbestos Fibers in Drinking Water

Techniques are available to minimize the concentration of asbestos fibers in drinking water. Filtration research conducted at locations on Lake Superior and in the Cascade Mountains in Washington has shown that amphibole and chrysotile fibers can be removed by granular media filtration. Removal percentages can exceed 99% when the raw water is coagulated properly and the filtered water turbidity is 0.10 ntu (nephelometric turbidity units) or lower. Filtered water fiber counts below detectable limits of 0.1 to 0.01 X 10(6) fibers/L can be attained. A study by the Metropolitan Water District of Southern California showed that when raw water chrysotile counts ranged from 200 X 10(6) fibers/L to 2000 X 10(6) fibers/L, filtered water fiber counts frequently exceeded 1 X 10(6) fibers/L. Even so, striving to attain a filtered water turbidity of 0.1 ntu resulted in improved fiber removal. Pilot scale and distribution system research projects have shown that asbestos cement (AC) pipes can be protected from dissolution and leaching effects that can result in release of asbestos fibers into drinking water. Suggested techniques include modifying low pH, low alkalinity waters so they are not aggressive; coating the pipe wall with a chemical precipitate; and applying a cement mortar lining to the pipe wall. Operation and maintenance practices related to the distribution system, when AC water mains are in service, can influence the fiber count in tapwater. Main flushing can stir up sediment that accumulates in low-flow and dead-end areas, raising the fiber count. If mains are tapped and the cuttings are not flushed away through the tapping machine, but are instead permitted to fall into the water main, the fiber count can be raised.

Engineering and operating approaches for controlling asbestos fibers in drinking water.

Techniques are available to minimize the concentration of asbestos fibers in drinking water. Filtration research conducted at locations on Lake Superior and in the Cascade Mountains in Washington has shown that amphibole and chrysotile fibers can be removed by granular media filtration. Removal percentages can exceed 99% when the raw water is coagulated properly and the filtered water turbidity is 0.10 ntu (nephelometric turbidity units) or lower. Filtered water fiber counts below detectable limits of 0.1 to 0.01 X 10(6) fibers/L can be attained. A study by the Metropolitan Water District of Southern California showed that when raw water chrysotile counts ranged from 200 X 10(6) fibers/L to 2000 X 10(6) fibers/L, filtered water fiber counts frequently exceeded 1 X 10(6) fibers/L. Even so, striving to attain a filtered water turbidity of 0.1 ntu resulted in improved fiber removal. Pilot scale and distribution system research projects have shown that asbestos cement (AC) pipes can be protected from dissolution and leaching effects that can result in release of asbestos fibers into drinking water. Suggested techniques include modifying low pH, low alkalinity waters so they are not aggressive; coating the pipe wall with a chemical precipitate; and applying a cement mortar lining to the pipe wall. Operation and maintenance practices related to the distribution system, when AC water mains are in service, can influence the fiber count in tapwater. Main flushing can stir up sediment that accumulates in low-flow and dead-end areas, raising the fiber count. If mains are tapped and the cuttings are not flushed away through the tapping machine, but are instead permitted to fall into the water main, the fiber count can be raised.