New ATSDR Silica Study Profiles Adverse Health Affects
The Agency for Toxic Substances and Disease Registry (ATSDR), part of the Centers for Disease Control and Prevention (CDC), recently released a toxicological profile for silica. Silica is a common mineral that is a constituent of a number of construction materials, including sand, stone, concrete, brick, mortar, and polyurethane. However, silica, and particularly airborne silica dust, has been associated with a number of adverse health impacts, primarily resulting from use in the workplace. The ATSDR profile is an in-depth study that characterizes the toxicology and adverse health effects linked to silica.
Silica is generally found in two forms: crystalline and amorphous. Both types of silica are found in many commercial products, such as bricks, mortar, plaster, caulk, concrete, roofing materials, wallboard, granite, and engineered-stone counter tops. Inhalation of silica dust can be damaging to employee health and is of most concern to employers and employees. Examples of ways employees can be exposed to silica dust include:
Health effects that have been associated with occupational exposure to silica include silicosis (a progressive, fibrotic lung disease), chronic obstructive pulmonary disease (COPD), lung cancer, renal toxicity, increased risk of tuberculosis, and autoimmune diseases. Of these, silicosis and lung cancer pose the greatest risk and concern to human health, but these are typically associated with long-term or chronic exposures.
As a reminder, occupational exposures to respirable crystalline silica are regulated by the Occupational Safety and Health Administration (OSHA) as a toxic and hazardous substance by regulation 29 C.F.R. § 1910.1053 – Respirable crystalline silica. This section applies generally to all occupational exposures to silica, while a separate section, 29 C.F.R. § 1926.1153 – Respirable crystalline silica, applies specifically to occupational exposures in construction work and activities. The former regulation sets a Permissible Exposure Limit (PEL) for employees of 50 µg/m3, calculated as an 8-hour time-weighted Average (TWA). Employers must ensure that no employee is exposed to an airborne concentration of respirable crystalline silica in excess of that value over an 8-hour period.
An ATSDR toxicological profile is intended to examine, summarize, and interpret the latest data and information related to a specific toxic substance of concern, in this case silica. The profile reviews peer-reviewed data and information, and it seeks to determine the types or levels of exposure that may present significant risks of adverse health effects, or where gaps in such information may exist. In this case, there is a comprehensive review of the information available for silica. It remains to be seen if this information will lead to any changes in the current regulations regarding exposure limits. In the meantime, this report provides greatly detailed toxicological information for those interested in or who deal with potential silica exposure in their workplace. For more information, a link to the ATSDR website for the silica report chapters can be found here, and the full report can be downloaded here.