Safe Exposure Limits for Mica: Paul DeLeo and Kristian Fried to Present Study Results at SOT Meeting

If you work with mica, the results are in: historical lifetime worker exposure levels have been protecting you. An Integral Consulting study of historical data and current literature shows dramatic respiratory disease declines of more than 90 percent since the 1970s, when the effects of worker protection limits made in the 1950s were first evident.

Kristian Fried, Ph.D., DABT, Dr. rer. nat., ERT, and Paul DeLeo, Ph.D., authored the study, which they will present at the Society of Toxicology (SOT) virtual meeting during a live poster session on March 18, from 1:00 to 2:45 p.m. Eastern.  The SOT virtual meeting is from March 12 through 26, 2021, and attendees can view the poster at any time.

Mica is a chemically inert phyllosilicate mineral with a wide range of applications.

Mica is a chemically inert phyllosilicate mineral with a wide range of applications. In the early 20^th century, workers would contract respiratory diseases such as pneumoconiosis from inhalation exposure to mica from mining processes like crushing and milling.  This is why the exposure level for mica was among the first limits set by the American Conference of Governmental Industrial Hygienists (ACGIH) in 1946. Integral’s study was to evaluate whether the occupational exposure level that was revised in 1951 and that remained essentially unchanged for the following 70 years was safe—and if a recent 30-fold reduction by ACGIH is scientifically justified.

The study “Preventing pneumoconiosis: Review of a safe level for lifetime occupational inhalation exposure to mica,” evaluated historical records of pneumoconiosis rates in the U.S. workforce with respect to the long latency period for disease manifestation.  The study found that the historical occupational exposure limit of 3 mg/m³ for respirable particles was scientifically justified and protective of workers’ health.

For more information on the study, contact Dr. Fried at kfried@integral-corp.com or Dr. DeLeo at pdeleo@integral-corp.com.