3-mercaptopropionic acid

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999-10-20 to 2000-03-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Remarks:

Hessisches Ministerium fuer Umwelt, Energie, Jugend, Familie und Gesundheit

Analytical monitoring:

yes

Details on sampling:

Samples were drawn from the test solutions and analyzed on the same day of collection.

Vehicle:

no

Details on test solutions:

dilution water according to DIN 38412, part 11

The test substance was introduced into the dilution water whilst stirring by aid of a magnetic stirrer for 10 min. The maximum concentration applied was 1000 mg/L. Within the definitive main test concentrations of 100, 50, 25, 12.5, and 6.25 mg/L of the test substance were used.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna STRAUS
- Source: bred in the laboratory of the test facility (originally derived from Dr. Knie, LWA Duesseldorf)
- Age at study initiation: not older than 24 hours
- Method of breeding:
- Feeding during test: test animals were not fed during the test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

20 +/- 1°C;
determined at the beginning and the end of the test in each treatment group, see below ("remarks on results including tables and figures")

pH:

determined at the beginning and the end of the test in each treatment group, see below ("remarks on results including tables and figures")

Dissolved oxygen:

determined at the beginning and the end of the test in each treatment group, see below ("remarks on results including tables and figures")

Nominal and measured concentrations:

nominal test item concentrations (mg/L): 100, 50, 25, 12.5, 6.25, and 0 (control);
the single measured test item concentrations are not reported (the biological effects based on measured concentrations are reported; see below)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed (glass stoppers)
- Material, size, headspace, fill volume: glass, 250 mL, no headspace, approx. 290 mL
- Aeration: no active aeration
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): no vehicle used


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dilution water according to DIN 38412, part 11


OTHER TEST CONDITIONS
- Photoperiod: light : dark : 16:8 hours


EFFECT PARAMETERS MEASURED: immobility


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.0

Reference substance (positive control):

yes

Remarks:

potassium dichromate (tested in a separate study)

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

17 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: geom. mean of meas. conc. between t=0h and t=48h

Details on results:

corresponding EC values based on nominal test item concentrations:
48 hour EC0 / EC50 / EC100 (mg/L): 6.5 / 17 / 46
24 hour EC0 / EC50 / EC100 (mg/L): 8.3 / 31 / 110

Results with reference substance (positive control):

A reference substance was not tested as a direct parallel to the study with the test item.

Nevertheless, the sensitivity of the test system towards toxic substances is verified once a month with potassium dichromate. The value of the EC50 in this period of time was 1.5 mg/L K-dichromate.

Reported statistics and error estimates:

Numbers of immobilized Daphnia were plotted against the respective concentration. Using a validated computer program on the basis of EXCEL 5.0, the EC50 value was determined as well as the EC100 and the NOEC together with the 95% confidence limits.

Immobilization data in the time course of the test (20 Daphnia per test concentration):

Conc. of test substance (mg/L)	Ratio immobilized Daphnia (%)
Control (0)	0 [0/20]	0 [0/20]
100	100 [20/20]	100 [20/20]
50	75 [ 15/20]	100 [20/20]
25	40 [8/20]	80 [16/20]
12.5	0 [0/20]	25 [5/20]
6.25	0 [0/20]	0 [0/20]

Numbers in brackets are the absolute numbers of animals immobilized at each concentration.

Physical parameters data in the time course of the test:

Conc. of test substance (mg/L)	PH value		O2 content (mg O2/L)		Temperature (°C)
	0 h	48 h	0 h	48 h	0 h	48 h
Control (0)	7.25	7.16	8.0	7.8	19.0	21.3
100	4.95	5.48	8.1	7.8	19.0	21.3
50	6.77	6.98	8.1	7.8	19.0	21.3
25	6.97	7.20	8.2	7.8	19.0	21.3
12.5	7.05	7.24	8.2	7.8	19.0	21.3
6.25	7.09	7.30	8.2	7.8	19.0	21.3

 

Calculated EC values based on the geometric mean measured concentrations (as recommended by OECD Guidance Document No. 23):

	24 h	48 h
EC0	5.2 mg/L	2.4 mg/L
EC50	21 mg/L	9 mg/L
EC100	88 mg/L	35 mg/L

(For each concentration, the geometric mean for the measured concentrations between t0 and t48 h were used)

Calculated EC values based on nominal concentrations:

	24 h	48 h
EC0	8.3 mg/L	6.5 mg/L
EC50	31 mg/L	17 mg/L
EC100	110 mg/L	46 mg/L

 

Chemical analysis of the test solutions performed with freshly prepared test solutions and after 48 h of incubation demonstrated that the test substance was partially oxidized, and thus there are two components, the original test substance and the oxidation product, present in the test solution.

Sampling time (h)	Concentration of Test Substance (mg/L)
	Nominal	Measured
0	0 (control)	nd
0	100	104
0	50	53
0	25	24
48	0 (control)	nd
48	100	90
48	50	32
48	25	6

nd = no peaks detected
The samples were drawn from the test solutions and analyzed the same day of collection.

All validity criteria for the test were met.

Validity criteria fulfilled:

yes

Conclusions:

The following EC-values were calculated on basis of the nominal concentrations being tested: 24 h EC50 = 31 mg/L, 48 h EC50 = 17 mg/L

Executive summary:

3-Mercaptopropionic acid was tested for acute toxicity towards Daphnia according to OECD 202, Part I. In order to investigate the influence of the test substance towards the daphnia, the swimming behaviour of the animals was recorded. Under the conditions used for the test, immobilisation of the daphnia was observed at concentrations >12.5 mg/L. The following EC-values were calculated on basis of the nominal concentrations being tested: 24 h EC50 = 31 mg/L, 48 h EC50 = 17 mg/L

Within TOC-analyses performed with a test solution freshly prepared in tap water, and after 96h (this is the time schedule for a fish toxicity test), it could be shown, that the organic matter of the test substance remained constant in the aqueous phase. Upon chemical analyses of test solutions performed with freshly prepared test solutions and after 48h of incubation it could be demonstrated, that the test substance was partially oxidized, and thus there are two components, the original test substance and the oxidation product, present in the test solution. It cannot be distinguished between a toxic effect of the original test substance and the oxidation product because they are both present in the test solution representing also a dynamic process. For this reason, the results of this test are based on the nominal concentrations tested. As an alternative calculation (not recommended by the OECD Guideline 202 Part D using the measured concentration of the original test substance 3-mercaptopropionic acid, the following EC-values were calculated: 24 hEC50 = 14 mg/L, 48 h EC50 = 4 mg/L

These values do not represent the real environmental conditions because the test substance is rapidly oxidized by the oxygen content in the aqueous phase.

Description of key information

EC50 (48 h) = 17 mg/L (Daphnia magna)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

17 mg/L

Additional information

3-Mercaptopropionic acid was tested for acute toxicity towards Daphnia according to OECD 202, Part I. In order to investigate the influence of the test substance towards the daphnia, the swimming behaviour of the animals was recorded. Under the conditions used for the test, immobilisation of the daphnia was observed at concentrations >12.5 mg/L. The following EC-values were calculated on basis of the nominal concentrations being tested: 24 h EC50 = 31 mg/L, 48 h EC50 = 17 mg/L

Within TOC-analyses performed with a test solution freshly prepared in tap water, and after 96h (this is the time schedule for a fish toxicity test), it could be shown, that the organic matter of the test substance remained constant in the aqueous phase. Upon chemical analyses of test solutions performed with freshly prepared test solutions and after 48h of incubation it could be demonstrated, that the test substance was partially oxidized, and thus there are two components, the original test substance and the oxidation product, present in the test solution. It cannot be distinguished between a toxic effect of the original test substance and the oxidation product because they are both present in the test solution representing also a dynamic process. For this reason, the results of this test are based on the nominal concentrations tested. As an alternative calculation (not recommended by the OECD Guideline 202 Part D using the measured concentration of the original test substance 3-mercaptopropionic acid, the following EC-values were calculated: 24 hEC50 = 14 mg/L, 48 h EC50 = 4 mg/L

These values do not represent the real environmental conditions because the test substance is rapidly oxidized by the oxygen content in the aqueous phase.