Ball clays are hydrous aluminum silicates of approximate formula Al2O3, 2SiO2 2H2O. They are inert (insoluble, non-flammable, non-decomposing, non-polymerizing) and non-toxic by ingestion. See 'Silica' for more information.
Ball clays contain free quartz, in some cases up to 25%. Do not breathe dust. Prolonged inhalation even at low levels may cause delayed lung injury (silicosis). Follow guidelines for Crystalline Silica (Quartz).
IARC Monograph Volume 42, 1987 concludes that "there is a limited evidence for the carcinogenicity of crystalline silica in humans". IARC classification 2A. The NTP Sixth Annual Report on Carcinogens, 1991, has added crystalline silica to its list of substances that are "reasonably anticipated to be carcinogens".
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