Registration Dossier

Administrative data

Workers - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
6.8 mg/m³
Most sensitive endpoint:
repeated dose toxicity
Route of original study:
By inhalation
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
Overall assessment factor (AF):
45
Modified dose descriptor starting point:
NOAEC
DNEL value:
307 mg/m³
AF for dose response relationship:
1
Justification:
default
AF for differences in duration of exposure:
6
Justification:
extrapolation form sub-chronic to chronic
AF for interspecies differences (allometric scaling):
1
Justification:
default for inhalation
AF for other interspecies differences:
2.5
Justification:
default
AF for intraspecies differences:
3
Justification:
Eurometaux (2010) recommends for metals
AF for the quality of the whole database:
1
AF for remaining uncertainties:
1
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
low hazard (no threshold derived)
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:
no hazard identified

Additional information - workers

The most relevant routes of potential exposure to workers would be the dermal and inhalation routes. Based on the available acute toxicity data (oral, dermal, inhalation), tungsten dioxide is not likely an acute toxicant, and therefore, derivation of DNEL long-term will be sufficient to control potential risks associated with short-term exposures. In addition, based on the available data, WO2 is not likely irritating to either the eyes or skin, or sensitizing to the skin. Therefore, based on the available data, WO2 does not appear to elicit local toxicity effects. As such, derivation of a DNEL for local effects is not necessary.

No repeat-dose toxicity data are available for WO2; however, a 28-day inhalation toxicity study is available on TBO, which is used for read-across and is considered the key long-term study for derivation of the DNELs. In this study, 5 rats/sex/dose were given TBO nose-only for 6 hours per day, 7 days/week, for 28 days at doses of 0 (control), 0.08, 0.325, and 0.65 mg TBO/L air. The NOAEC was deemed to be greater than 0.65 mg TBO/L air (650 mg/m³). The starting dose of 650 mg TBO/m³ needed to be modified, as the experimental animals were exposed for 6 hrs per /day, whereas workers are exposed for 8 hrs per /day. In addition, for occupational exposure, the starting point needs to be modified to correct for respiratory volume under standard conditions (6.7 m³/person) versus under conditions of light activity for workers (10 m³/person). Based on ECHA’s recommendations, it is assumed that respiratory absorption is equivalent between the animals and humans. Therefore, the corrected dose is 330 mg TBO/m³. Because WO2 and TBO have a slightly different molecular weight (WO2 vs. WO2.9-2.99), for purposes of calculation of the DNEL it will be assumed that 330 mg TBO/m³ is equivalent to 307 mg WO2/m³. An interspecies assessment factors for the inhalation route of 2.5. is used. Eurometaux (2010) recommends an AF of 3 for intraspecies variability in workers, which is based on the ECETOC task force’s analysis of the intraspecies variability of toxicokinetic and toxicodynamic parameters from human data. To account for extrapolation from a subacute study to chronic, ECHA recommends using an AF of 6.

The overall AF used to derive the systemic DNELlong-term for the inhalation route for the worker is 45 (2.5 x 3 x 6).

Worker DNELlong-term for the inhalation route = 307/45 = 6.8 mg WO2/m³ (equal to 5.8 mg W/m³). It should be noted that the inhalation DNELlong-term for the worker of 5.8 mg W/m³ is consistent with the current threshold limit value (TLV) for tungsten Metal and insoluble compounds of 5 mg W/m³. It should also be noted that this DNEL is not based on a NOAEL but on the highest dose tested on a 28day study which did not elicit an adverse effect. Thus the DNEL is over conservative and only meant to be indicative.

A systemic DNELlong-term for the dermal route for the worker has not been derived. Based on the available data for the dermal route the potential for acute and local effects is low. In addition the systemic toxicity is assumed to be negligible based on an oral NOAEL of 75 mg Na2WO4/kg/d derived from a 90 day feeding study in rats. The systemic toxicity of both compounds (WO2 and N2WO4) is based on free Tungsten. The water solubility of WO2 is very low and about two orders of magnitude lower than that for Na2WO4. Thus, a corrected NOAEL would exceed the limit dose of 1000 mg/kg/d.

General Population - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information

General Population - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified

General Population - Hazard via oral route

Systemic effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:
no hazard identified

Additional information - General Population

Tungsten dioxide is used only in an industrial setting. Exposure to the general population is not expected.