[1,2,4]Triazolo[1,5-a]pyrimidine-2-sulfonamide, N-(2,6-difluorophenyl)-5-methyl-

Toxicity to aquatic algae and cyanobacteria

Description of key information

An algae toxicity study (Hughes JS (1991)) was conducted using Selenastrum capricornutum. The study showed that the 5-day EC25 was 2.86 µg/L (95% CL 2.25 - 3.62 µg/L) and the 5 day EC50 was 4.93 µg/L (95% CL 4.17 - 5.82 µg/L). The observed effect concentration (NOEC) based upon the mean standing crop values on day 5 was determined by an analysis of variance and Dunnett's test to be 0.36 µg/L.
Four additional algae toxicity studies were also available (Hughes JS & Alexander MM (1992a), Hughes JS & Alexander MM (1992b), Hughes JS & Alexander MM (1992c) and Hughes JS & Alexander MM (1992d)) on Navicula pelliculosa, Anabaena flos-aquae, Skeletonema costatum and Lemna gibba respectively. The first three studies gave 5 day EC50 values of 51.1 mg/L , 0.167 mg/L and 61.3 mg/L  respectively and in the case of Lemna gibba, a 14 day EC50 of ≥5.1 and ≤5.6 µg/L. Although of equal reliability to the key study (Klimisch 2), these studies were not selected as key as they did not represent a worst case result and were conducted on species that are less commonly used to address this REACH endpoint. As such, they are provided as supporting information.

Key value for chemical safety assessment

EC50 for freshwater algae:

4.93 µg/L

EC10 or NOEC for freshwater algae:

0.36 µg/L

Additional information

The key study was chosen on a worst case basis and was also performed on typical algae species used to address this endpoint. The study was performed according to an EPA guideline and was in line with GLP standards. It was considered robust enough to be a key study.

The four supporting studies were all reliable tests performed to EPA guidelines. All showed high levels of toxicity to aquatic algae.