Thiram

Toxicity to aquatic algae and cyanobacteria

Description of key information

ErC10 (72 h): 56.9 µg a.i./L (geometric mean, OECD 201, static, Pseudokirchnerella subcapitata)

ErC50 (72 h): > 141 µg a.i./L (geometric mean, OECD 201, static, Pseudokirchnerella subcapitata)

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

56.9 µg/L

Additional information

One key study investigating the toxicity of tetramethylthiuram disulfide (CAS No. 137-26-8) to algae, is available.

 

Effects of tetramethylthiuram disulfide (CAS No. 137-26-8) on the growth of a freshwater green algae (Pseudokirchneriella subcapitata) applied at 5 dose rates with nominal concentrations of 47, 74, 119, 191 and 304 µg a.s./L was observed over a period of 72 hours in a static test system (OECD 201, GLP). Three replicate flasks at each test concentration, a solvent control and six control replicate flasks (Algal Growth (AAP-) Medium alone) were included in the test. The test item was analytically monitored at time points 0, 24, 48 and 72 h. The analytical verification of the test item confirmed a recovery of Thiram in the test solutions at test termination in a range from 5 to 14% of nominal concentrations. Therefore, the results of the study are based on geometric mean measured concentrations of 20, 29, 43, 75 and 141 µg a.i./L. Concentration dependent effects on growth rate and yield were observed. Exposure of P. subcapitata to the highest concentration of 141 µg/L caused a maximum inhibition of growth rate and yield of 37% and 84%, respectively. The 72-hour EC50 values for growth rate and for yield were calculated to be > 141 µg a.i./L (geom. mean measured) and 69.5 µg a.i./L (geom. mean measured), respectively. The 72-hour EC10 values for growth rate and yield of P. subcapitata were determined as 56.9 µg a.i./L (geom. mean measured) and 28.9 µg a.i./L (geom. mean measured), respectively. NOEC (72 h) values were determined to be 29 µg a.i./L (geom. mean measured) for both growth rate and yield.

 

Furthermore, one study investigating the toxicity of tetramethylthiuram disulfide (CAS No. 137-26-8) to algae species with minor reliability (RL3) is available. A reevaluation of the data revealed that not all validity criteria are met according to the recent OECD Guideline No. 201 (version 2011). The mean coefficient of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3, for 72-hour tests) in the control cultures reached 68.8% and by that exceeded the maximum of 35%, given as validity criterion in the guideline.

 

The results from the key study are considered more reliable and were used for the hazard and risk assessment.