Ziram

Endpoint summary

Additional information

Several studies testing the biodegradation of the substance zinc bis dimethyldithiocarbamate (CAS No. 137-30-4) in different systems are available.

Biodegradation of zinc bis dimethyldithiocarbamate (CAS No. 137-30-4) in the screening test reached 7.7% after 28 d and therefore, the substance is considered as not readily biodegradable. However, some inhibitory effects of the substance towards microorganisms were observed.

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

The key water simulation study (according to OECD 309 ) was performed with a high and a low nominal test item concentration of 100 µg/L and 10 µg/L and incubated for 30 days. The total mean recoveries of the applied radioactivity were sufficient based on the guideline (> 90%). After 30 d, mineralization (formation of CO2 and CS2) reached a maximum of 31.5% AR (high dose) and 56.9% AR (low dose). 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. Total recoveries of the test substance obtained during incubation were sufficient and exceeded 90% of applied radioactivity. The test material rapidly degraded in both systems, with DT50 values of 0.3 days and 0.2 days (0.6 and 0.4 d at 12°C) for river and pond systems, respectively. Thiram (CAS No. 137-26-8) was found as a major intermediate degradation product. The mineralization rate (formation of 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 was performed according to OECD 307. Total mean recovery of radioactivity during the 28-day incubation period accounted for 97.1% ± 4.7% of applied radioactivity (AR). Under aerobic conditions zinc bis dimethyldithiocarbamate was completely dissipated by day 1. Besides the test item, two major fractions, Thiram and M1.1, were detected. M1.1 was initially detected at time 0 with mean amounts of 11.5% AR, reaching maximum mean amounts of 34.9% AR on day 1, and subsequently decreased to 11.1% AR at the end of incubation (day 28). Besides, a number of minor fractions were detected. None of the remaining fractions exceeded a mean amount of 5.7% AR (M1.11, day 1) at any time throughout the study. The calculated test item DT50 value was determined to be 0.6 day, corresponding to 1.4 days at 12 °C. Mineralization rate of the substance reached 53.2% after 28 days. Comparable 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 days).

For a brief overview of the key data on biodegradation refer to attached document below.