Sodium chromate

Endpoint summary

Description of key information

High quality (NTP) studies using oral dosing are available for sodium dichromate and potassium dichromate in the rat and mouse.  Repeated dose inhalation exposure studies are available for chromium trioxide.  Longer term toxicity and carcinogenicity studies are also availabel for compounds in this group

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

LOAEL

1.7 mg/kg bw/day

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Dose descriptor:

LOAEC

1.81 mg/m³

Additional information

Repeated dose oral toxicity

No studies of repeated dose oral toxicity are available for chromium (VI) trioxide, however studies are not required as the primary route of occupational exposure is likely to be inhalation. Reliable repeated dose studies are available, however, for potassium dichromate and sodium dichromate and the results of these studies can be extrapolated to the other members of the group.

Two NTP combined repeat dose / reproductive toxicity screening studies have been performed with potassium dichromate in the rat and mouse; the studies used dietary administration for up to 9 weeks. Although there was some evidence for a treatment-related effect on erythrocyte parameters in both studies, findings were of small magnitude and were not considered to be of toxicological significance. Findings of toxicological significance were limited to reduced bodyweight gain in male mice at the high dose level of 400 ppm (32 mg/kg bw/d Cr (VI)).

Two NTP 90-day carcinogenicity sighting studies were performed with sodium dichromate in the rat and mouse using administration in drinking water. The results of these studies show effects on bodyweight and food consumption and (most markedly), a microcytic hypochromic anaemia consistenet with an effect of Cr (VI) on iron homeostasis and/or haemoglobin synthesis. Histopathology revealed local irritant effects on the gastric mucosa. Findings were apparent at the lowest dose levels in these studies, equivalent to 1.7 and 3.1 mg/kg bw/d Cr (VI) in the rat and mouse respectively.

Repeated dose dermal toxicity

No studies of repeated dose dermal toxicity are available for this group of compounds, however the relevance of such studies to human occupational risk assessment will be severely limited by the corrosive nature of the compound. In practice, human dermal exposure will also be self-limiting. Given the corrosivity and the low dermal penetration of these compounds, findings in repeat-dose dermal toxicity studies will be limited to local (site of contact) effects; systemic effects are not predicted with the exception of non-specific effects secondary to local corrosivity. Additionally, performing repeated dose dermal toxicity studies cannot be justified on animal welfare grounds.

Repeated dose inhalation toxicity

The results of two published repeated exposure inhalation studies in the mouse (Adachi et al, 1986; Adachi, 1987) performed over periods of up to 12 months show that the primary effects of exposure are local corrosion and irritation of the respiratory tract. Findings were observed in mice following exposure to a concentration of 3.63 mg/m3 for 30 minutes, twice a week for up to one year; or in mice exposed to concentrations of 1.81 mg/m3 for 60 minutes, twice a week for one year. The results of this study can be extrapolated to the other compounds in this group.

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: hematopoiesis

Repeated dose toxicity: inhalation - systemic effects (target organ) respiratory: other

Repeated dose toxicity: dermal - systemic effects (target organ) other: skin

Justification for classification or non-classification

Chromium trioxide, sodium dichromate, potassium dichromate and sodium chromate are listed on Annex I of Directive 67/548/EEC and are classified as (R48/23) ' Toxic: danger of serious damage to health by prolonged exposure through inhalation'. No change to this classification is proposed.