Potassium dimethyldithiocarbamate

Endpoint summary

Additional information

Experimental data from tests investigating the toxicity of KDDC to terrestrial organisms were not conducted since studies from similar analogues are considered suitable for this purpose in accordance with the specifications listed in Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances and read across, on basis of structural similarity, physico-chemical properties, ecotoxicological profiles. There is no convincing evidence that any one of these chemicals might lie out of the overall profile of this analogue approach, respectively. Conclusions regarding this section were drawn based on studies performed on SDDC (sodium dimethyldithiocarbamate, CAS No. 128-04-1) and Ziram (zinc bis(dimethyldithiocarbamate), CAS No. 137-30-4). KDDC, SDDC and Ziram represent salts of dimethyl dithiocarbamic acid (DDC) that are capable of dissociating into the respective ions when exposed to water. The main differences between Ziram and KDDC/SDDC are the solubility in water and partition coefficient related to the rather covalent character of the zinc-sulphur bond with respect to the sodium-sulphur bond. The physico-chemical parameters of the three substances are listed in the table below.

Table 2. Physico-chemical parameters of KDDC, SDDC and Ziram

Parameter	KDDC	SDDC	Ziram*
Molecular weight	159.3 g/mol	143.2 g/mol	305.8 g/mol
Melting point	Partial melting from 81.5 to 85.0°C followed by slow decomposition	Decomposition at ≥ 253°C	251.0 – 252.5°C Colour change beginning at 238°C
Relative density at 20°C	1.51	1.4	1.7097
Vapour pressure at 25°C	8.76×10^-5Pa	< 2×10^–4Pa	1.8×10^–5Pa
Log Pow at 20°C	read across to SDDC	pH 5: = –3.2 pH 7: < –2.28 pH 9: < –2.33	1.65 pH range: 7.4-8.6[1]
Water solubility	read across to SDDC	37.4 - 40% (w/w) pH 10.5	9.67×10^–4g/L pH range: 7.2-7.4^1

*data are not presented within this dossier, but where subject to the respective REACh-registration of Ziram (CAS: 137-30-4, EC: 205-288-3)

An acute earthworm study is available for the analogue showing the highest resemblance to KDDC, i.e. SDDC. The remaining terrestrial endpoints were covered by data of Ziram. This approach can be considered as a worst-case scenario, since the comparison between SDDC and Ziram in a) aquatic toxicity tests (see technical dossier chapter 6.1) and b) for the terrestrial compartment (in acute earthworm studies),showed significantly lower effect concentrations for Ziram than those for SDDC (LC₅₀(14d) = 140 mg a.i./kg soil (dw)* for Ziram and LC₅₀(14d) = 787.6 mg a.i./kg soil (dw) for SDDC, respectively).

Based on the results from the studies performed on the analogue substances, KDDC may cause toxic effects to some terrestrial organisms (e.g. Eisenia fetida: NOEC of 4.053 mg a.i./kg dw soil).

The table below summarizes the effects of the analogue substances Ziram and SDDC to terrestrial organisms:

Table 4. Ecotoxicological data of SDDC and Ziram in the terrestrial compartment

Endpoint	Test duration	Effect value	Substance
Toxicity to soil macroorganisms except arthropods	14d	LC50 = 787.6 mg a.i./kg soil d.w.	SDDC
Toxicity to soil macroorganisms except arthropods	56d	NOEC = 4.053 mg a.i./kg soil d.w.	Ziram
Toxicity to terrestrial arthropods	48 h	LD50 > 100 µg per animal	Ziram
Toxicity to terrestrial plants	21 d	NOEC = 9 kg/ha	Ziram
Toxicity to soil microorganisms	56d	NOEC = 40 kg/ha	Ziram
Toxicity to birds	14 d	LD50 = 97 mg /kg bw	Ziram
Toxicity to birds	5 d	LC50 = 5156 mg/kg diet	Ziram
Toxicity to birds	20 wk	NOEC > 500 mg/kg diet	Ziram