Final Toxicological Profiles for Silica, Thorium Published

The Agency for Toxic Substances and Disease Registry has published final toxicological profiles for silica and thorium. ATSDR’s toxicological profile for silica describes the health effects of exposure to both crystalline silica and non-crystalline amorphous silica. A section that discusses populations with potentially high exposures details the variety of industries and occupations in which workers are at risk for high occupational exposures to silica. These include metal, nonmetal, and coal mines and mills; hydraulic fracturing operations; construction; rubber and plastics; counter manufacture and installation; and automobile repair.

Thorium is a radioactive substance that occurs naturally in the environment. According to ATSDR, workers in the uranium, thorium, tin, and phosphate mining, and gas mantle production industries may be exposed to higher levels of the substance. Individuals who breathe air near facilities where uranium, phosphate, or tin ore is processed may also be exposed to thorium. The agency warns that studies on thorium workers have shown that breathing high levels of thorium dust increases a person’s chance of getting lung disease. Similarly, workers who had high exposures to cigarette smoke, radon gas, and thorium had cancers of the lung, pancreas, and blood.

ATSDR toxicological profiles characterize the toxicology and adverse health effects information for hazardous substances. Each peer-reviewed profile identifies and reviews the key literature that describes a substance's toxicological properties. Health and toxicologic information on the potential for human exposure; chemical and physical properties; regulations and guidelines; and production, import, use, and disposal can also be found in ATSDR’s toxicological profiles. A full list of toxic substances with published profiles is available on the agency’s website.