Spackle is a compound of powder that contains glue and gypsum powder. When the two are mixed with water it turns into a plastic paste that is used to repair holes in plaster. Until 1970, spackle was often made with asbestos because of its ability to resist fire and insulate. In fact, starting in about 1930, some forms of spackle were put on walls and ceilings with a trowel to make creative the creative patterns that were popular at that time.
The problem lies when this spackle starts to deteriorate or is sanded or even removed. When these things happen the asbestos is released into the air in the form of dust that can be easily inhaled. The tiny fibers in the dust can become stuck in the lungs and the linings of certain organs. The result of this can be mesothelioma, which is an incurable cancer. It is usually fatal, in part because the symptoms take decades to appear and are often initially mistaken for something else.
These days, people who work in remodeling and demolition are at risk for exposure to asbestos in not just the spackle but also the many other products that probably contain asbestos in structures built between 1900 and 1980. There are guidelines for both the EPA and OSHA that ensure careful handling of asbestos repairs, which must be professionally done only by licensed contractors.