Tungsten trioxide

Neurotoxicity

Description of key information

The following information is taken into account for any hazard / risk assessment: No neurotoxicity data of sufficient quality are available for tungsten trioxide (target substance). However, neurotoxicity data are available for sodium tungstate (source substance), which are used for read-across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read-across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach description in the Category section of this IUCLID submission or Annex 3 of the CSR.

The neurotoxicity potential of sodium tungstate is reported by two publications by Sachdeva et al, 2015 and Radcliffe et al, 2009. An inhalation study reported that sodium tungstate is not appreciably transported via the olfactory pathway to the brain following a single 90-min exposure in rats, although this pathway is known to transport a number of other metals (Radcliffe et al, 2009). Sodium tungstate exposure was reported in one study to produced oxidative stress in brains from rats exposed. However, the study did not elucidate and correlate these oxidative changes with behavioral and functional alterations (Sachdeva et al, 2015).

 

Key value for chemical safety assessment

Effect on neurotoxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

125 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

Well documented scientfically sound study similar to OECD guidelines with sufficient information provided on materials and methods to evaluate results. However as this study is used in the context of a read across, Klimisch 2 is assigned.

Effect on neurotoxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Well documented scientfically sound study with sufficient information provided on materials and methods to evaluate results. However as this study is used in the context of a read across, Klimisch 2 is assigned.

Effect on neurotoxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

No neurotoxicity studies are available for tungsten trioxide. However, data were available on sodium tungstate, which are used for read-across. The sodium tungstate neurotoxicity studies are more investigative reports conducted under no standard testing guidelines which limit their usability for regulatory purposes. Based on this, none of the data from these publications warrant any classification for sodium tungstate and subsequently tungsten trioxide as neurotoxicants per CLP as more information is needed.