Cement refers to a material that sets and hardens, and can bind other materials together. The most common type is Portland cement, which is created by heating limestone to 1450 degrees Fahrenheit and adding other materials, including gypsum. Portland cement can then be used as a base to form other blended cements, which will harden even in inclement weather or underwater.
Before 1973, asbestos was regularly used in siding cement because of its ability to provide strength with flexibility and its characteristic of being fireproof. It was mixed into the cement as a binder to provide the ½-inch thickness that is required for siding. Asbestos cement is made with ten percent asbestos, plus sand and Portland cement. Once mixed, it could be molded or cast into siding shingles, roofing tiles, and other items.
Asbestos and Cement Plants
Before the early 60s, amosite or crocidolite asbestos was used for making the siding cement. After the early 60s, these materials were replaced with chrysotile asbestos. This elevates the risks of cement plant workers who were employed before the mid-70s of developing mesothelioma or asbestosis. According to a medical study that was conducted in 1987 on different cement plants, the results showed that workers who worked with amosite/crocidolite asbestos had slightly more cases of asbestos cancer compared to workers who worked with chrysotile asbestos, although both types present a considerable risk for health issues. Chrysotile asbestos was often contaminated with another type of asbestos that contained amphibole fiber. The fibers that were found in amosite and crocidolite asbestos when studied close-up appear as hard, long needles. When ingested or inhaled these sharp fibers burrow under soft tissue.
Medical researchers are still unclear why malignant mesothelioma occurs, but they do understand that the sharp fibers can burrow deep within the lungs and with time find their way to any part of the body. Because research suggests that these fibers tend to interact with the DNA of cells, this can cause them to become malignant. Another risk factor that increases the chances of developing this form of cancer is smoking. Individuals who were exposed to asbestos and smoke have a 9000 times higher chance of developing this cancer than those who do not smoke.