Registration Dossier

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The lowest reliable observed EC10-value for respiration (inhibition of respiration after a 3h  incubation period) using activated sludge was, 216.5 mg Mo/L (HRC, 1994d).  Test was conducted with molybdenum trioxide (MoO3) as test substance.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
216.5 mg/L

Additional information

Data on the toxicity tests performed with aquatic bacteria and protozoa, reported as EC50, EC10 and NOECs are summarized below. It can be noted that there are insufficient useful data for aquatic micro-organisms to apply statistical extrapolation. From the extracted results, two test results were considered relevant for deriving the PNEC for micro-organisms in STPs: the activated sludge test with pure MoO3(HRC, 1994) and the activated sludge test with sodium molybdate (Stearns, 1985). As the second study resulted in the highest, unbounded NOEC (i.e., > 950 mg/L), the derivation of a PNECmicro-organism is based on the HRC (1994) study.

 

Test species / inoculum

Test compound

Test medium

Exp.time

Endpoint

End parameter

Result (mg Mo/L)

Reference

Bacteria – accepted studies for the determination of a PNECSTP

 

 

 

 

 

 

 

 

 

 

Domestic activated sludge population

MoO3, technical

activated sludge + artificial sewage

3 hour

EC50

Inhibition of respiration

1926

Huntington Research Center, 1994c

Domestic activated sludge population

MoO3pure

activated sludge + artificial sewage

3 hour

EC50

EC10

Inhibition of respiration

546

216.5 (169.1-277.3)

Huntington Research Center, 1994d

Domestic activated sludge population

Sodium molybdate

activated sludge

30 min

NOEC

Oxygen utilization

BOD-removal

> 950

Stearns, 1985

Domestic activated sludge population

Sodium molybdate

activated sludge

30 min

NOEC

Sludge dewatering

< 950

Stearns, 1985

Bacteria – rejected studies for the determination of a PNECSTP

 

 

 

 

 

 

 

 

 

 

Pseudomonas putida

NaMoO4dihydrate

Artificial

18 h

EC50

Cell multiplication (≈ growth)

50

Huntington Research Center, 1994a

Pseudomonas putida

Ammonium molybdate

Artificial

18 h

EC50

Cell multiplication (≈ growth)

13

Huntington Research Center, 1994b