Propane-1,3-diol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

P. putida

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Qualifier:

according to guideline

Guideline:

DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest)

GLP compliance:

yes

Test organisms (species):

Pseudomonas putida

Test type:

static

Total exposure duration:

16 h

Test temperature:

20±2°C

pH:

At test start:
Control - 7.25
10 g/L - 7.05

After 16 hours:
Control - 6.62
10 g/L - 6.45

Nominal and measured concentrations:

Nominal concentrations: 0, 6, 8, and 10 g/L

Details on test conditions:

After preparation of the test solutions, they were divided into 4 equal amounts of 90 mL, four of which were filled into Erlenmeyer flasks (except in the case of the highest test concentrations, where all 5 portions were used). Parallel to the mixtures with the test substance, 30 mL of solution II and solution III respectively and 60 mL of solution IV were added to 960 mL of demineralized water and this control solution was divided into 12 portions of 90 mL each. The solution II to IV were prepared according to DIN 38412, Part 8.

The test solutions were injected to 10% with an inoculum of Pseudomonas putida MIGULA in the exponential growth phase, resulting in a total volume of 100 mL of test solution. During incubation and to avoid contamination, the test solutions were closed with cotton wool plugs, that were pervious to air. A reagent zero value was determined for each concentration by replacing the inoculum with the test medium.

The initial cloudiness of the control solutions before incubation was determined by means of a photometer to be 436 nm and then the solutions were incubated for 16±1 hours at 20±2°C, whilst being shaken. The pH value was determined in one control solution an in one test solution and in one test solution with the highest concentration.

After completion of the incubation the extinction of the control at 436 nm and therefore the bacterial density was determined, in order to detect the minimum bacterial proliferation in the control solution. The pH value was determined in one control solution and in one test solution with the highest concentration.

In order to determine the inhibiting effect of the test substance on the test system the test solutions were measured by means of a photometer to be 436 nm against the control without any test substance.

Solution I
20.0 g NaNO3
4.8 g K2HPO4
2.0 g Yeast extract
2.4 g KH2PO4
Dissolved in 1 L of deionized water.
--
Solution II
20.0 g NaNO3
4.8 g K2HPO4
2.4 g KH2PO4
Dissolved in 1 L of deionized water.
--
Solution III
88.0 g Glucose-Monohydrate
Dissolved in 1 L of deionized water.
--
Solution IV
4.0 g MgSO4 x 7 H2O
0.01 g Iron citrate
Dissolved in 1 L of deionized water.

Duration:

16 h

Dose descriptor:

EC50

Effect conc.:

11 g/L

Duration:

16 h

Dose descriptor:

NOEC

Effect conc.:

6 g/L

Duration:

16 h

Dose descriptor:

EC10

Effect conc.:

8 g/L

Validity criteria fulfilled:

yes

Conclusions:

16-hour NOEC: 6 g/L
16-hour EC50: 11 g/L

Executive summary:

1,3-Propanediol was investigated for chronic bacterial toxicity according to DIN 38412, Part 8. After 16 hours incubation time, the bacterial density of Pseudomonas putida was determined in the test solutions and compared with a control solution without test substance. Under the conditions of the study, the EC50 value was determined as 11 g/L and the NOEC value was determined to be 6 g/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

6 000 mg/L

Additional information

Pseudomonas putida, a species commonly found in environmental and wastewater treatment samples, is considered representative of a microbial respiration inhibition study. A chronic bacterial toxicity study on P. putida was determined to have a NOEC value of 6000 mg/L. In addition, the test substance was readily biodegraded in an OECD 301B study conducted at 42.2 mg/L with a microbial inoculum from a municipal wastewater treatment plant. If microbial toxicity would have occurred at this concentration biodegradation of the test substance would be hampered. However, the test substance is found to be readily biodegradable. The P. putida NOEC value provides an additional margin of safety to confirm that this test substance will not inhibit sewage treatment plant microorganisms.