Zinc, [1,2,3-propanetriolato(2-)-.kappa.O1,.kappa.O2]-, homopolymer, stereoisomer

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

No test data on the toxicity to microorganisms are available. Under environmental conditions the organometallic substance will partly dissociate into the zinc cation and the glycerol anion. A comparison of the acute LC50 and EC50 values for soluble zinc [cf. to the current registration dossier of CAS 1314-13-2, 2017] for the test substance and glycerol [OECD SIDS 2002] indicate that the acute aquatic toxicity of zinc is considerably higher than that of glycerol while the toxicity of zinc and the test substance are in the same range. For this reason and the fact that zinc dissolved from the test substance, zinc will be the causative factor for toxicity and not glycerol. Therefore, the environmental risk assessment based, as a worst-case scenario, on different zinc salts. Several data were available for this endpoint. Formerly (ECB 2008), and in the REACH-registrations of a number of zinc substances of November 2010, a PNEC of 52 µg/L for STP was derived, based on the lowest EC50 of 5.2 mg Zn/L observed in a sludge respiration inhibition test (Dutka et al. 1983). According to the guidance (ECHA 7.8.17.1) preference should be given to nitrification inhibition because respiration inhibition is a less sensitive endpoint. A study conducted by Juliastuti et al. (2003) reported a NOEC of 0.1 mg Zn/L in an ISO 9509 nitrification inhibition test. Applying the rules for PNEC setting (ECHA R.10, table R.10.6) this result yields a PNEC STP of 100 µg Zn/L (AF of 1).

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

4 h

Dose descriptor:

NOEC

Effect conc.:

0.1 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

inhibition of nitrification rate

Description of key information

A nitrification inhibition test with Zn sulfate on activated slugde originating from a municipal wastewater treatment plant was performed leading to a NOEC of  100 µg Zn/L.

Depending on local conditions and existing concentrations, disturbances in the biodegradation process of activated sludge are possible.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 µg/L

Additional information

No test data on the toxicity to microorganisms are available. Under environmental conditions the organometallic substance will partly dissociate into the zinc cation and the glycerol anion. As a worst case approach the hazard potential for the present compound is therefore derived from zinc sulfate.

Several data were available for this endpoint. Formerly (ECB 2008), and in the REACH-registrations of a number of zinc substances of November 2010, a PNEC of 52 µg/L for STP was derived, based on the lowest EC50 of 5.2 mg Zn/L observed in a sludge respiration inhibition test (Dutka et al. 1983). According to the guidance (ECHA 7.8.17.1) preference should be given to nitrification inhibition because respiration inhibition is a less sensitive endpoint. A study conducted by Juliastuti et al. (2003) reported a NOEC of 0.1 mg Zn/L in an ISO 9509 nitrification inhibition test. Applying the rules for PNEC setting (ECHA R.10, table R.10.6) this result yields a PNEC STP of 100 µg Zn/L (AF of 1).