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 DNELlong-term for sodium tungstate, from which all other soluble tungsten substance DNELs were derived, is 3 mg sodium tungstate/m(3) (1.7 mg W/m(3)), and the inhalation DNELlong-term for tungsten blue oxide, from which all other sparingly soluble tungsten substance DNELs were derived, is 7.3 mg tungsten blue oxide/m(3) (5.8 mg tungsten/m(3)). Although derived using different methodologies and supported by different studies, the occupational inhalation DNELslong-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/m(3) for soluble tungsten compounds and 5 mg tungsten/m(3) as metal and insoluble tungsten compounds.

An update to the toxicological profile for water-soluble and sparingly soluble tungsten substances

“…Neurobehavioral assessment of pups born and nursed from WO 4 2− -exposed rats found elevation of distress vocalizations in the 125 mg/kg/d group, and the righting reflex showed unexpected sex-dependent differences (but not dose-dependent), where male pups demonstrated faster righting than females ( McInturf et al 2008 , 2011 ). When looking closer at these results, it can be noted that the statistical difference observed in the righting reflex between male and female pups was due to a decrease in male righting reflex with increasing dose (but not statistically significant), combined with a numerical increase in the righting reflex among females ( Jackson et al 2013 ).…”

“…Using the studies done by McCain et al (2010) and Rajendran et al (2012) , Jackson et al (2013) calculated the values of derived no effect levels (DNELs) for occupational long-term inhalation, according to the REACH program's guidance on characterization of dose-response for human health. The inhalation DNEL long-term for ST, from which values for all other soluble tungsten substance DNELs were derived, is 3 mg/m 3 (1.7 mg tungsten/m 3 ), and the inhalation DNEL long-term for WO 2.91 is 7.3 mg/m 3 (5.8 mg tungsten/m 3 ).…”