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EC number: 200-018-0 | CAS number: 50-21-5
The acute toxicity of the test material, a solution of about 80 % L-(+)-lactic acid, to the fresh-water crustacean Daphnia magna was determined as described in the OECD guideline no. 202 and according to the OECD principles of Good Laboratory Practice.
The test was carried out with 4 × 5 daphnias (quadruplicate test solutions) at each concentration, and the test solutions were not replaced. The exposure duration was 48 hours. The nominal concentrations tested were 32, 56, 100, 180, 320 and 560 mg/L.
At the start of the test the test substance appeared to be completely dissolved at all concentrations tested (visually assessed).
The actual concentrations of L-(+)-lactic acid were determined enzymatically with a Boehringer test kit. They were between 42 and 76 % of nominal just after dosing (average 59 %). To test the stability, the concentrations of L-(+)-lactic acid were also analysed at the end of the test and were between 58 and 78 % of nominal (average 71 %).
The results of the test were (as nominal concentrations):
24 h EC50 (mobility): 240 mg/L
48h EC50 (mobility): 240 mg/L
48h EC100 (mobility) 320 mg/L
The 48-h EC50 based on measured concentrations was 130 mg/L.
This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Results are based on nominal concentrations.
The acute toxicity of lactic acid to Daphnia magna was assessed using the methods outlined by the Committee on Methods for Toxicity Tests with Aquatic Organisms. Water quality parameters of temperature, dissolved oxygen and pH were measured at the termination of the test and were within acceptable limits.
The results of the 48 hour static Daphnia magna toxicity study is: LC50 (48h) = 750 mg/L. All reported values were based upon nominal concentrations. The no effect level observed for SY-83 was 320 mg/L after 48 hours, which was based on the lack of mortality and abnormal effects.
In a 48-h acute toxicity study, water fleas (Daphnia magna) were exposed to L-(+)-lactic acid at nominal concentrations of 0 (control), 320 and 560 mg/L (further information on the number of concentration levels not available) under static conditions. The 48-h EC50 was 240 mg/L. The observed effects can be attributed to a pH effect. Sublethal effects were not reported. Based on the results of this study, L-(+)-lactic acid would not be classified as hazardous to the aquatic environment according to the CLP Regulation (EC) No 1272/2008.
This toxicity study is classified as supplementary information and does not satisfy the guideline requirement for an invertebrate short-term toxicity study but can nevertheless be used as supportive data or in a weight-of-evidence approach.
Test organism: Water flea (Daphnia magna)
Test type: Static
EC50: 240 mg/L
Endpoint(s) effected: Mobility
This information is used in a read-across approach in the assessment of the target substance.For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
In short-term toxicity test on lactic acid in water fleas immobilisation was observed resulting in estimated EC50 values ranging between 130 and 750 mg/L (nominal) which can be attributed to a pH effect. Lactate as such is considered not to exert any systemic effects on daphnids in the tested concentration range of up to 750 mg/L.
In three studies on short-term toxicity of lactic acid to water fleas immobilisation was observed resulting in estimated EC50 values ranging between 130 (measured) and 750 mg/L (nominal). All studies are relatively poorly documented and therefore reliable only with restrictions. However, they can be used in a weight-of-evidence approach. In one of the studies (Bowmer et al., 1998) the observed mortality was explicitly attributed to pH effects: pH at the test concentrations of 320 and 560 mg/L was measured to be 4.1 and 3.5.
The theoretical pH shift caused by lactic acid at the lowest identified EC50 of 130 mg/L (= 1.443 mmol/L), considering a pKa of 3.9, would result in a final pH of 3.43. This compares quite well to the measured pH values of 4.1 and 3.5 at test concentrations of 320 and 560 mg/L in a slightly buffered system (Bowmer et al., 1998).
Therefore, the immobilisation observed in the available short-term tests on water fleas can undoubtfully be attributed to a pH shift instead of being a toxic effect of the lactate ion/molecule. Accordingly, since any toxic effects of the lactate are of interest instead of acidification it can be concluded that within the tested concentration range (up to 750 mg/L) lactic acid does not cause adverse effects on invertebrates, except pH related toxicity. A key value (EC50) for chemical safety assessment hence cannot be identified.
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