Sodium dimethyldithiocarbamate

Toxicity to aquatic algae and cyanobacteria

Description of key information

ErC10 (72 h) = 0.74 µg a.i./L (geom. mean measured, OECD 201, N. pelliculosa)

ErC50 (72 h) = 1.2 µg a.i./L (geom. mean measured, OECD 201, N. pelliculosa)

Key value for chemical safety assessment

EC50 for freshwater algae:

1.2 µg/L

EC10 or NOEC for freshwater algae:

0.74 µg/L

Additional information

Three GLP studies are available, in which the toxicity ofsodium dimethyldithiocarbamate (CAS128-04-1)to aquatic algae was assessed according to OECD guideline 201.

In the first key study (Liedtke, 2012), the freshwater green alga Pseudokirchneriella subcapitata was exposed to five nominal test item concentrations in a geometric series with a spacing factor of 2 ranging from 15.63 to 250 µg/L for 96 h. The pH of the stock solution was adjusted with 0.1 M NaOH because the test item was not stable at neutral pH. Therefore, a solvent control was additionally included.

The measured test item concentrations were between 70 and 83% of the nominal values at the start of the test and between 12 to 24% of the nominal values at the end of the test. Since the test item, was not stable in the test media over the duration of the test, the results were based on the geometric mean measured test item concentrations. The determined ErC50 (72 h) and ErC10 (72 h) were 11 and 6.1 µg a.i./L, respectively.

In the second key study (Arnie, 2018), the diatom Naviculla pelliculosa was exposed to five nominal test item concentrations in a geometric series with a spacing factor of approximately 2.5 ranging from 1.0 to 100 µg a.i./L for 96 h. Test item concentrations were analytically verified by GC/MS after 0, 72 and 96 h.

At 0 h, the measured test item concentrations ranged from 71.7 to 123% of nominal values. At 72 h, the measured concentrations ranged from < LOQ to 57.2% of nominal. After 96 h, the measured concentrations were all < LOQ. This observed decline in measured concentrations indicates that the test item was not stable for the duration of the test. Therefore, results were based on the geometric mean measured concentrations of 0.64, 0.84, 1.3, 8.7, 22 and 80 µg a.i./L, equivalent to 64, 32, 21, 54, 54, and 80% of the nominal concentrations.

After 72 h, inhibition of growth rate in the 0.64, 0.84, 1.3, 8.7, 22 and 80 µg a.i./L treatment groups was -1, 20, 56, 73, 74, and 79%, respectively, relative to the negative control. Inhibition of yield in the 0.64, 0.84, 1.3, 8.7, 22 and 80 μg a.i./L treatment groups was -6, 72, 97, 99, 99, and 99%, respectively, relative to the negative control. Based on the geometric mean measured concentrations, the ErC10 (72 h) was 0.74 µg a.i./L, the ErC50 (72 h) was 1.2 µg a.i./L and the corresponding NOEC (72 h) was 0.64 µg a.i./L.

In the supporting study (Van der Kerken, 2003) the algal cells were exposed to the test material at seven different concentrations and effects on biomass and growth were determined at 72 and 96 hours (exponential growth was maintained). The 72 h-ErC50 and NOEC values were 0.25 and 0.10 mg a.i./L, respectively. Algae started to grow again when they were placed in fresh nutrient medium. Thus test substance is algistatic rather than algicidal.

In conclusion, the lowest experimentally determined effect concentrations are retained as key values for the toxicity ofsodium dimethyldithiocarbamate (CAS128-04-1)to aquatic algae, which include an ErC10 (72 h) of 0.51 µg a.i./L and an the ErC50 (72 h) was 0.72 µg a.i./L (geometric mean measured, OECD 201, N. pelliculosa).