Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Solubility and stability of Arsenic acid in water

 

The available data on arsenic acid indicate a high solubility of the substance with a value of 302 g/L in water. This means that the ranges of testing concentrations are far below the solubility limit of Arsenic in water. 

 

Moreover, Henry’s law constant (H) quantifies the partitioning of chemicals between the aqueous phase and the gas phase.

For chemicals with H values less than 0.01 Pa m3/mole, the chemical is less volatile than water and as water evaporates the concentration of the chemical in the aqueous phase will increase; for chemicals with H values around 100 Pa m3/mole, volatilisation will be rapid.

For arsenic acid, the H value was calculated to be 0.868 Pa m3/mole at 25 °C (EUSES calculations based on the Vapour pressure = 1845 pa, water solubility = 302 g/L and mol. weight = 142 g/mol).

 

Therefore, based on his physico-chemical properties, Arsenic acid is not expected to volatilise.

 

Moreover, several in several studies the tested concentrations were measured analytically. The recoveries were quite high (more than 90%) indicating a good solubilisation of the test substance.

 

Based on these observations it can be concluded that the test substance arsenic acid stays in solution in water. Therefore the absence of concentrations monitoring is not invalidating for the aquatic studies.

 

Arsenic acid toxicity to aquatic organisms

 

A large set of data on aquatic toxicity of arsenic acid is available.

 

Large differences of toxicity were observed between the tested species. Individual studies as well as data reviews are available.

The validated references are listed in the table below.

 

Freshwater organisms

 

Species

Test duration/ conditions

Endpoint

Result (mg/L)

Reference

Fish

Rainbow trout, juvenile

Rainbow trout,alevin

96 h

96 h

LC50

LC50

= 67.5

> 360

Buhl KJ & Hamilton SJ (1990)

Fathead minnow (Pimephales promelas)

96h

LC50

25.6

Eisler R (1988)

Fathead minnow (Pimephales promelas)

35 d

LOEC

NOEC

1.9

0.97

Machado M.W

Rainbow trout, juvenile

 

24 weeks

NOEC

13 µg As/g diet

Cockell K.A (1991)

Daphnia

Daphnia pulex

96h

LC50

3.4

Theegala, C. S. (2007)

Daphnia magna

96h

NOEC

44.66 mg/l (35.22-50.93)

Fargasova A., (1994)

Daphnia pulex

21d

NOEC

> 1

Theegala, C. S. (2007)

Daphnia pulex

26d

LOEC

 

NOEC

0.020 arsenate = 10.5 arsenic

5 µg/L As

Chen, CY (1999) cited in Lepper P., 2007

Algae and other aquatic plants

Scenedesmus obliguus

96h

EC50

0.159

Chen, F (1994) cited in Lepper P., 2007

Asterionella

24 d

NOEC

0.160

ConwayHL (1978)

Ankistrodesmus falcatus

14 d

EC50

NOEC

0.256

0.01

Vocke, R.W. (1980)

Scenedesmus obliquus

14 d

LC50

0.048

Vocke, R.W. (1980)

Selenastrum capricornutum

14 d

LC50

NOEC

30.7

12

Vocke, R.W. (1980)

Microorganisms

Pseudomonas putida

16h

EC10

6.75

Bringmann, G (1976)

 

Marine organisms

 

Species

Test duration/ conditions

Endpoint

Result (mg/L)

Reference

 

 

 

 

 

Sheepshead minnow (cyprinodon vertegatus)

96 h

LC50

NOEC

28

13

Lelievre, M.K. (1990)

Mysid shrimp (Mysidopsis bahia)

96h

LC50

2

Lelievre, M.K. (1990)

Strongylocentrotus purpuratus

48 h

LOEC

EC10

0.011

0.006

Garman(1997) cited in Lepper P., 2007

Skeletonema costatum

6 d

LOEC

0.013

Sanders J.G. (1979) cited in Lepper P., 2007

Conclusion:

 

The available toxicity data on freshwater and marine organisms belong to the same growth order. The lowest long term data belong to the range 5-10 µg/L and were observed on invertebrate and algae species.