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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
ca. 240 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 95 % CL = 180-320
Details on results:
- Behavioural abnormalities: No data
- Observations on body length and weight: No data
- Other biological observations: No data
- Mortality of control: No data
- Other adverse effects control: No data
- Abnormal responses: No data
- Effect concentrations exceeding solubility of substance in test medium: No
Validity criteria fulfilled:
not specified
Conclusions:
The short-term toxicity testing of lactic acid on freshwater invertebrates (Daphnia magna) resulted in an EC50 (48 h) of 240 mg/L (nominal), which can be attributed to a pH effect.
Executive summary:

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.

Results synopsis

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.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
ca. 320 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
ca. 750 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Validity criteria fulfilled:
not specified
Conclusions:
The LC50 (48h) of Daphnia magna equals 750 mg/L.
Executive summary:

The acute toxicity of lactic acid (SY-83) 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 result 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 lactic acid (SY-83) was 320 mg/L after 48 hours, which was based on absence of mortality and abnormal effects.

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.

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
130 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
250 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Details on results:
Test solutions were not neutralised. Effects on the mobility of the daphnids are hence likely to be caused by the pH shift.
Validity criteria fulfilled:
yes
Conclusions:
The 48 h EC50 (immobilisation) of lactic acid to Daphnia magna is 130 mg/L, elicited by the pH shift.
Executive summary:

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.

 

Description of key information

There are no reliable studies available for the assessment of the short-term toxicity to aquatic invertebrates endpoint with the target substance D-lactide itself. Therefore, available data from a short-term toxicity to aquatic invertebrates study conducted with a suitable read-across partner, L(+)-lactic acid, was used to assess this endpoint.

In short-term toxicity test on L(+)-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.

For details and justification of read-across plase refer to the report attached in section 13 of IUCLID.

Key value for chemical safety assessment

Additional information

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.

Since D-lactide undergoes immediate hydrolysis in contact with water, forming lactic acid, this is the moiety of interest by read-across. Both L- and D-lactic acid are ubiquitous and essential molecules in all biological systems, and organisms are continuously exposed to significant internal and external background concentrations of L- as well as D-lactic acid. Therefore, the information on the aquatic toxicity of L-lactic acid is fully valid for D-lactic acid, and in consequence for D-lactide.