Barium chromate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.005 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.005 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.005 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

10 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

31 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

31 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

3.2 mg/kg soil dw

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

17 000 g/kg food

Assessment factor:

10

Additional information

Since the background concentration in the ecotoxicological test media is negligible, the PNEC total and the PNEC added are considered to be equal.

BaCrO4 is a salt and will release Ba or Cr ions (transformation products via hydrolysis, dissociation,…). These ions will be responsible for any potential environmental and human systemic effect, rather than the initial non-transformed substance.

Barium and chromium are both natural elements, natural part of the earth’s crust and present in natural background concentrations in all environmental compartments.

 

Due to several physico-chemical processes, chromium can exist in different chemical forms, some of which are more bioavailable and toxic than others (depending on pH, hardness and dissolved organic matter, for instance). In particular, a significant difference may exist between Cr(VI) and Cr(III), which are the most stable oxidation states of chromium at pH range of natural waters. Once Cr (VI) is released in the environment, reduction will occur. Cr(VI) can be removed naturally in water by reductants such as aqueous Fe(II), dissolved humic acids, and Fe(II)-bearing minerals and Cr(III) will be formed. Cr (VI) in the air reacts with dust particles or other pollutants to form Cr(III). The environmental effects assessment is therefore based on the Cr(III) assessment.

 

As widely reported in relevant chromate assessments (i.e. RAR 2005, INERIS 2005), in aquatic environment, adsorption of Cr(VI) to particulate matter decreases when pH increases and competing dissolved anions are present. On the other hand, Cr(III) adsorption increases with pH and decreases where competing dissolved cations are present. Under the same conditions, Cr(III) adsorption to particulate matter is higher than Cr(VI). In sediment, reduction of Cr(VI) to Cr(III) is expected in anaerobic sediments: at environmental pH, adsorption of Cr(III) to sediment is likely to occur and when pH decreases below 5, Cr(III) becomes more mobile.

The behaviour of Cr(VI) in soil is similar to its behaviour in sediment compartment. Adsorption to the soil matrix is expected to increase with increasing acidity of the soil. Under neutral to alkaline conditions Cr(VI) is expected to become highly mobile in soil. Furthermore, it may leach into anaerobic layers where reduction to Cr(III) would be expected. As for sediment, Cr(III) is expected to be rapidly and strongly adsorbed into soil. In groundwater, Cr(VI) is reduced to Cr(III) in presence of low oxygen concentration or reducing conditions.

 

For human health, it can not be assumed that Cr (VI) is rapidly reduced to the less toxic Cr (III) and consequently, Cr (VI) is assumed for human health