Cancer Hazard. Contains quartz (crystalline silica) which may cause cancer. Risk of cancer depends upon duration and level of exposure to the dust. Not an acute hazard. Prolonged inhalation of dust may cause lung injury. Inhalation of high concentrations of dust may cause mechanical irritation and discomfort of the respiratory tract. Repeated exposure may have chronic effects. When cleaning up dry dust NIOSH or MSHA approved particulate filter respirators should be used. *Clay in moist form poses no health risk. Inhalation of dry clay dust should be avoided