Potassium dimethyldithiocarbamate

Endpoint summary

Additional information

Experimental data from tests investigating the fate of KDDC in the environment were not conducted since studies from a similar analogue are considered to be suitable for this purpose. Conclusions regarding this section have been drawn based on studies performed on SDDC (Sodium dimethyldithiocarbamate, CAS No. 128-04-1). Both KDDC and SDDC represent salts of dimethyl dithiocarbamic acid (DDC) that are capable of dissociating into the respective ions (K⁺and Na⁺) when exposed to water. The physico-chemical parameters of both substances are listed in the table below.

Table 1. Physico-chemical parameters of KDDC and SDDC

Parameter	KDDC	SDDC
CAS no.	128-03-0	128-04-1
IUPAC Name	potassium dimethyldithiocarbamate	sodium dimethyldithiocarbamate
Molecular weight	159.3 g/mol	143.2 g/mol
Molecular formula	C3H7NS2.K	C3H7NS2.Na
Melting point	Partial melting from 81.5 to 85.0°C followed by slow decomposition	Decomposition at ≥ 253°C
Relative density at 20°C	1.51	1.4
Vapour pressure at 25°C	8.76×10^-5Pa	< 2×10^–4Pa
Log Pow at 20°C	read across to SDDC	pH 5: = –3.2 pH 7: < –2.28 pH 9: < –2.33
Water solubility	read across to SDDC	37.4 - 40% (w/w) pH 10.5

Considering the similarities in molecular structure and characteristics of these two substances, an analogue approach from SDDC to KDDC is justified.

KDDC exhibits a low vapour pressure and low volatility. Therefore, photodegradation is not an important degradation pathway. Nevertheless, if emitted into the air, KDDC will be rapidly photodegraded (estimated half-life = 4.6 hours for indirect photodegradation, OH-radicals). Furthermore, based on the available information from the analogue substance, KDDC is expected to undergo rapid photolysis in water as well (half-life = 19 hours). Once released into the water phase, hydrolysis might contribute significantly to the degradation of this substance, especially under acidic and neutral conditions (half-lives of 0.6 h and 41.6 hours at pH 4 and 7, respectively).

KDDC is considered to be readily biodegradable and therefore, additional tests on biodegradation in water, sediment and soil are not deemed necessary. Based on the available information, this substance is not expected to persist in the environment.

The estimated Henry’s Law constant (<6.3×10^-08Pa m³/mol at 20 °C) indicates that KDDC will not tend to evaporate from the water surface. This substance has no potential for adsorption to solid particles (log Koc = -0.12) and based on its log Kow (<0) and estimated BCF (0.84), bioaccumulation in biota is not expected.