A Proposed Control Limit for Exposure to Airborne Erionite Fibers

Abstract

The unique physical and chemical properties of the zeolite minerals have resulted in their use in many industrial processes. Environmental exposures to erionite, a commonly fibrous zeolite, have been linked to elevated incidence of malignant pleural mesotheliomas and associated pleural disorders through epidemiological investigations. The presence of erionite in the workplace, with its documented relationship to elevated rates of pleural malignancies in environmentally exposed populations, requires that individuals exposed to the mineral during the course of their work take precautions to avoid excessive airborne exposures to the mineral. A review of relevant environmental, toxicological, and epidemiological literature was undertaken to quantify the effects of erionite exposure. This review identified erionite as a potent mesothelioma risk agent. The risks were compared to those accepted by the U.S. Department of Labor Occupational Safety and Health Administration in the promulgation of the current asbestos permissible exposure limit. We recommend an 8-hour exposure limit of 0.0007 fibers of erionite per cubic centimeter of air based on comparison of the mortality data from an environmentally exposed population with the excess mortality risk accepted by the Occupational Safety and Health Administration in the 1994 asbestos permissible exposure limit. The proposed control limit is readily measured by current analytical techniques and may be used to assess the adequacy of respiratory protective equipment and other control measures supplied to exposed worker populations.