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Short-term toxicity to aquatic invertebrates

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Description of key information

With regard to the total hardness and Ca2+ content, a EC50 (48 h)  value of 2.083 mg/L should be used for the classification of Lanthanum chloride, derived in ASTM medium according to OECD 202 with Daphnia carinata. 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
2.083 mg/L

Additional information

The acute toxicity of Lanthanum chloride on Daphnia carinata was investigated in three different media according to OECD 202 (Barry and Meehan 2000). Depending on the used media the EC50 values were strongly different.

 

The investigation using tap water (TW) as test medium with a low total hardness (22 mg/L CaCO3) showed a 48 h EC50 of Lanthanum chloride of 0.076 mg/L. Following this value the 48 h EC50 of 0.086 mg/L was measured in Daphnia water (DW), based on diluted sea water having a total hardness of 98 mg/L CaCO3. In contrast, the 48 h EC50 of Lanthanum chloride in the ASTM standard medium with the highest total hardness (160 mg/L CaCO3) was 2.083 mg/L (see table below). The results showed that the hardness of the test medium reveals a significant influence on the toxicity of Lanthanum chloride on Daphnia carinata.

 

The three media varied clearly in source and chemical composition, so without extensive testing of the various components, it is not possible to figure out the factors affecting toxicity. Nevertheless, it is well established that carbonate hardness can modify the toxicity of metals to aquatic organisms (for example Cooney, 1995, Yim et al. 2006) and this may be one important factor in determining the toxicity of Lanthanum chloride to Daphnia. The total calcium concentration of the test water may be another factor affecting the toxicity because La3+ behaves much like Ca2+ in biological systems (Evans, 1983). Hardness above 140 mg/l (as CaCO3) for testing on cladocerans is recommended by Cowgill (1990). Tests at this level and above have demonstrated reproductive performance in compliance with the validity criteria.

 

Compared to the tap water, the Daphnia medium and the Elendt M4 and M7 medium the hardness of ASTM medium is moderate and compatible to standard test conditions.

Since the test result which is the most related to standard conditions should be taken for classification consideration, the 48 h effect concentration of 2.083 mg/L tested in the ASTM medium is applied for the classification of Lanthanum chloride.

 

The following table shows the total hardness of the three tested media in comparison with Elendt M4 and M7 medium proposed by the OECD 202 Guideline:

Medium

Total hardness (as mg/L of CaCO3)

48-h EC50

mg/L

Tap water (Barry and Meehan, 2000))

22*

0.076

Daphnia water (Barry and Meehan, 2000)

98*

0.086

ASTM medium (ASTM, 1992)

160*

2.083

Elendt M4 and M7 medium (OECD, 202)

approx. 250**

-

* measured

** theoretical value

 

Toxicity data for marine species are not available.

 

Cooney, J.D. (1995). Freshwater tests. In: Rand, G.M. (Ed.), Fundamentals of Aquatic Toxicology. Effects, Environmental Fate, and Risk Assessment, second ed..& Francis,, pp. 71-98.

Long KE et al. (2004). The effects of low hardness and pH on copper toxicity to Daphnia magna.Environ Toxicol Chem.2004 Jan;23(1):72-5.

Evans, C.H. (1983). Interesting and useful biochemical properties of lanthanides. TIBS December, 445 -449.

Cowgill, U.M. and Milazzo, D.P. (1990) The sensitivity of two cladocerans to water quality variables: salinity and hardness. Arch. Hydrobiol., 120(2): 185-196.