Ziram

PBT assessment

PBT assessment: overall result

Reference

Reference 1

Name:

Ziram

Type of composition:

legal entity composition of the substance

State / form:

solid: particulate/powder

Reference substance:

Ziram

Reference 2

Name:

zinc bis(dimethyldithiocarbamate)

Type of composition:

boundary composition of the substance

State / form:

solid: particulate/powder

Reference substance:

zinc bis(dimethyldithiocarbamate)

PBT status:

the substance is not PBT / vPvB

Justification:

The PBT assessment of the substance is based on the criteria set out in the “Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT Assessment” (2017).

Persistence (P):

Zinc bis dimethyldithiocarbamate (CAS No. 137-30-4) is not readily biodegradable according to the OECD criteria. Several higher tier studies investigating the degradation of the substance in water column, sediment/water and soil compartments are available.

The substance hydrolyses with specific half-lives of 10.4 min (pH 5), 17.67 h (pH 7) and 6.31 d (pH 9). The main degradation product at pH 5 and 7 was carbon disulfide (CS2) whereas at pH 9 dimethyldithiocarbamic acid (DDC) and several minor metabolites were detected.

Furthermore, simulation studies are available assessing the degradation of zinc bis dimethyldithiocarbamate in water, sediment and soil.

The available simulation study in water (OECD 309), was performed with a high and a low nominal test item concentration of 100 and 10 µg/L and incubated for 30 days. Mineralization (CO2 and CS2) reached a maximum of 31.5% AR (high dose) and 56.9% AR (low dose) after 30 d. The difference in the mineralization rates could be attributed to an inhibitory effect on microorganisms in the higher dose application system, as observed in further studies with microorganisms. The derived DT50 value based on test material analysis for the high dose system of 100 µg/L was 2.47 days (5.8 days at 12°C). Moreover, on the basis of mineralization rate, as set out in the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11: PBT/vPvB assessment (2017), the substance can be considered as not persistent or very persistent in freshwater, since its presumed mineralization half-life (based on mineralization rate of 56.9% AR in 30 days) was reached within 40 d (if mineralization rate is above 50% at 30 days, it is assumed that the mineralization DT50 of the test item is equal or below 30 days).

The key sediment simulation study (according to European Community Commission Directive 95/36/EC, Annex I, 7.2.1, Route and Rate of Degradation in Aquatic Systems, 1995) was performed with two different water/sediment systems (pond and river) and incubated for 101 days. The mineralization rate (CO2 and CS2) reached 48.6% of the total applied radioactivity (AR) in the pond system and 84.2% AR in the river system after 101 d. Thus, on the basis of the criteria set out in the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11: PBT/vPvB assessment (2017), the substance can be considered as not persistent or very persistent in freshwater sediment, since its presumed mineralization half-life was reached within 120 d (presumed mineralization DT50 < 120 days).

The key simulation study in soil (according to OECD 307) resulted into a test item DT50 values of 0.6 day, corresponding to 1.4 days at 12 °C based on test item analysis. Mineralization of the substance reached 53.2% after 28 days. High mineralization rates were also reached in the supporting studies. Thus, on the basis of the criteria set out in the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11: PBT/vPvB assessment (2017), the substance can be considered as not persistent or very persistent in soil, since its presumed mineralization half-life was reached within 120 d (presumed mineralization DT50 < 120 day).

As a weight if evidence, it is concluded that zinc bis dimethyldithiocarbamate (CAS No. 137-30-4) is not considered to be persistent, as indicated by the presumed mineralization half-lives and does not meet the P and vP-criterion.

Bioaccumulation (B):

Zinc bis dimethyldithiocarbamate has a log Kow of 1.65 (EU Method A.8), which is below the trigger value of 3. The substance is not ionizable or surface active. Thus, the substance does not meet the screening criterion for bioaccumulation and is not considered to be bioaccumulative (B) or very bioaccumulative (vB).

 

Toxicity (T):

Based on the available data the substance is considered to be toxic. Screening criteria reveal L(E)C50 values of < 0.01 mg/L. Furthermore, the substance is classified as H373 according to Regulation (EC) No 1272/2008 and thus meets the T-criterion.

 

In conclusion, the substance is not PBT/vPvB.