Barium fluoride

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

147 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

no data: aquatic toxicity unlikely

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

79.4 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

766 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

265 mg/kg soil dw

Assessment factor:

2

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Barium fluoride will not exist in the environment as such, as it will rapidly dissociate to form barium and fluoride ions. Based on a comparison of the aquatic toxicity data summarized in this dossier, it is clear that the environmental risk assessment will be driven by the effects of barium rather than fluoride on. It is therefore considered appropriate to derive the PNEC values based on barium.

PNEC marine water:

A relevant PNEC for the marine environment cannot be determined, for the following reasons:

(i) Barium levels in sea water range from 2 to 63 μg/L with a mean concentration of about 13 μg/L (Bowen 1979).

(ii) Applying ECHA-guidance, the derived marine PNEC of 11.5 μg/L for barium (PNEC freshwater = 1.15 mg Ba/L and an AF of 100) would thus be within the range of typical barium seawater levels.

(iii) Seawater contains about 2700 mg/L sulfate (Hitchcock, 1975 cited in WHO, 2004).

(iv) Barium transported into marine systems combines with sulfate ions present in salt water to form barium sulfate.

(v) Barium in marine environments is in a steady state; the amount entering is balanced by the amount falling to the bottom as barium sulfate (barite) particles to form a permanent part of the marine sediment (Wolgemuth & Brocker, 1970). Thus, dissolved barium concentrations are controlled by the solubility of barium sulfate. The solubility product (K_sp) of barium sulfate is 1.08E^-10(CRC Handbook, 2008), resulting in maximum dissolved Ba levels of approximately 1.4 mg/L.

(vi) In sum, due to high sulfate levels in the marine environment and a low solubility of barium sulfate, dissolved barium levels will remain constant in marine waters, regardless of the amount of barium introduced to the system.

 

References:

- Bowen HMJ (1979) Environmental Chemistry of the Elements. Academic Press, London, 333 pp.

- Lide, D.R. (2008) CRC Handbook of chemistry and physics. 88^thedition.

- Hitchcock DR (1975) Biogenic contributions to atmospheric sulphate levels. In: Proceedings of the 2nd National Conference on Complete Water Re-use. Chicago, IL, American Institute of Chemical Engineers.

- WHO (1990) Barium. Environmental Health Criteria 107. International Programme on Chemical Safety.

- WHO (2004) Sulfate in Drinking-water. Background document for development of WHO Guidelines for Drinking-water Quality. WHO/SDE/WSH/03.04/114.

- Wolgemuth K & Broecker WS (1970) Barium in sea water. Earth planet. Sci. Lett., 8: 372-378.

PNEC sediment:

The PNEC_sedimentcan be derived from the PNEC_aquaticusing the equilibrium partitioning method (EPM).

A distribution/partition coefficient (K_D) between water and suspended matter for barium has been determined (see chapter 4). This resulted in a typical K_D,suspof 5,217 L/kg (logK_D: 3.72). In a first step the units have to be converted from L/kg to m³/m³using the formula below.

K_D,susp(m³/m³) = 0.9 + [0.1 x (K_D,susp(L/kg) x 2,500) / 1,000 ]

This results in a K_D,suspof 1,305 m³/m³. This value can be entered in the equation below to calculate the PNEC_sediment:

PNEC_sediment= (K_D,susp/ RHO_susp) x PNEC_aquaticx 1,000

with the PNEC_aquaticexpressed as mg/L, RHO_susprepresenting the bulk density of wet sediment (1,150 kg/m3) anda K_D,suspof 1,305 m³/m³, a PNEC_sediment that is expressed as mg/kg wet weight can be derived. This value can be converted to a dry weight-based PNEC, using a conversion factor of 4.6 kg wet weight/ kg dry weight.

This results in a PNEC_sedimentof 600.4 mg Ba/kg dry sediment

 

 

Conclusion on classification

Acute toxic effects of barium and fluoride released from BaF2 are relevant for the aquatic hazard assessment of Barium fluoride. Reliable acute and chronic toxicity data of barium and fluoride are available for three trophic levels: algae, invertebrates and fish, respectively. Based on these available results it may conservatively be assumed that the toxicological moiety of concern for the short- and long-term aquatic toxicity of BaF2 is barium.

Short-term toxicity EC/LC50 values of barium available for 3 trophic levels are situated between > 1.15 mg Ba/L and 14.5 mg Ba/L, corresponding to > 1.47 mg/L and 18.5 mg/L barium fluoride. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (a), classification for acute aquatic hazard is not required for barium fluoride as all EC50/LC50 values are above the classification criteria of 1 mg/L.

Long-term toxicity data are available for three trophic levels and range from ≥ 1.15 mg Ba/L to 2.9 mg Ba/L, corresponding to ≥ 1.47 mg/L and 3.7 mg/L barium fluoride. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (b) (i), classification for chronic aquatic hazard is not required for barium fluoride as all chronic EC10/NOEC values are above the classification criteria of 1 mg/L.