Asbestos in Braided Packing
Braided packing is used in plumbing applications, specifically for valves and pumps. It consists of braided yarn-like material (at the present time, usually carbon fiber) that contains a dispersion agent. In the past, this might have been paraffin or wax; today, graphite is the preferred material.
Through most of the twentieth century, the braided yarn used for packing was likely to have been made of asbestos fiber. Asbestos, although actually a form of rock, is very strong and durable, yet flexible enough to be woven into fabric, cord, etc.
Geologists have identified a number of asbestiform minerals, but only three have had any commercial value. These are chrysotile, crocidolite and amosite. Most asbestos used for braided packing was most likely of the chrysotile type. The most common diseases resulting from exposure to chrysotile are asbestosis, which results in a build-up of scar tissue inside the lungs, and mesothelioma.
Hazards Associated with Braided Packing Products
With most asbestos-based materials, the health risk to people comes from the potential to inhale asbestos fibers into the lungs. Asbestos braided packing is somewhat unusual in that the real exposure danger was not so much inhalation of fibers (the dispersion agent would have kept the fibers from escaping into the air) but ingestion through drinking water. Asbestos fibers in water supplies have been linked to gastrointestinal and kidney cancer in several North American communities. The braided packing material used in municipal water supply valves and pumps can break down over time, and when it does the tiny asbestos fibers can escape the dispersion agent and enter the drinking water.
Some industrial workers would encounter asbestos exposure risks from braided packing as well. Installers generally would not encounter excessive quantities of airborne asbestos, as they would usually be working with new, intact material, but repairmen, plumbers, maintenance personnel, and others that opened valves and pumps to work on them would have encountered degraded and damages asbestos braiding, and would often have removed such materials by hand prior to replacing it with new packing. For many years this type of work was done with little or no safety equipment and so even modest levels of exposure to braided packing could have resulted in significant asbestos risk.Sources
Bowker, Michael. Fatal Deception: The Untold Story of Asbestos (New York: Touchstone, 2003)
Sadler, Terry D. et. al. "The Use Of Asbestos-Cement Pipe For Public Water Supply and the Incidence of Cancer in Selected Communities in Utah." Journal of Community Health, vol. 9 no. 4 (Summer 1984)