Development Of Worker Inhalation Derived No Effect Levels For Tungsten Compounds

Abstract

Under the European Community (EC) Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), the risk to humans may be considered controlled if the estimated exposure levels to a substance do not exceed the appropriate derived no-effect level (DNEL). In order to address worker exposure, DNELs are derived for the worker population. The most significant route of exposure to workers to both soluble and sparingly soluble tungsten substances is through inhalation. In order to meet the REACH registration requirements, occupational long-term inhalation DNELs were developed according to the European Chemical Agency (ECHA) REACH guidance on characterization of dose-response for human health. The inhalation DNEL_long-term for sodium tungstate, from which all other soluble tungsten substance DNELs were derived, is 3 mg sodium tungstate/m³ (1.7 mg W/m³), and the inhalation DNEL_long-term for tungsten blue oxide, from which all other sparingly soluble tungsten substance DNELs were derived, is 7.3 mg tungsten blue oxide/m³ (5.8 mg tungsten/m³). Although derived using different methodologies and supported by different studies, the occupational inhalation DNELs_long-term for soluble and sparingly soluble tungsten compounds are similar to the current National Institute for Occupational Safety and Health (NIOSH) recommended exposure level (REL) and the American Conference of Industrial Hygienists (ACGIH) threshold limit value (TLV) 8-h time weighted average (TWA) of 1 mg tungsten/m³ for soluble tungsten compounds and 5 mg tungsten/m³ as metal and insoluble tungsten compounds.

Acknowledgments

The authors are grateful to the staff of IIT Research Institute (IITRI), the U. S. Army Center for Health Promotion and Preventative Medicine, for conducting many of the key studies used for derivation of the DNELs. Funding for some the research presented in this article was provided by the Tungsten REACH Consortium. All studies and results were developed in support of registration of tungsten compounds in accordance with the EU legislation on Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH).