Asbestos is a set of six naturally occurring silicate minerals which all have thin fibrous crystals, with each visible fiber composed of millions of microscopic "fibrils" that can be released by abrasion and other processes. They are commonly known by their colours, as "blue asbestos", "brown asbestos", "white asbestos" and so on.
It is now known that prolonged inhalation of asbestos fibers can cause serious and fatal illnesses including malignant lung cancer, mesothelioma and asbestosis. Health issues related to asbestos exposure can be found in records dating back to Roman times. By the beginning of the 20th century, concerns were beginning to be raised, which escalated in severity during the 1920s and 1930s. By the 1980s and 1990s, asbestos trade and use started to become banned outright, phased out or heavily restricted in an increasing number of countries.