4-chloro-o-xylene

Toxicity to aquatic algae and cyanobacteria

Description of key information

72 h hour ErC50 = 2.9 mg/L (95 % C.I. 2.6 - 3.2 mg/L), NOEC = 0.59 mg/L, OECD 201 (Boeri, 2004)

Key value for chemical safety assessment

EC50 for freshwater algae:

2.9 mg/L

EC10 or NOEC for freshwater algae:

0.59 mg/L

Additional information

In the key study, the effect of the test material on the growth of the green algal species Selenastrum capricornutum was investigated in a 72 hour static test conducted in accordance with the OECD Guideline No. 201 under GLP conditions.

The nominal concentrations were 0.33, 0.65, 1.3, 2.5 and 5.0 mg/L, along with a parallel control. The initial measured concentrations were 91 – 94 % of nominal concentrations. Final measured concentrations were 68 – 71 % of nominal concentrations, suggesting that the test material was not stable under test conditions. Results are therefore based on initial measured concentrations.

The algal population grew well, resulting in an average of 393 000 cells/mL in the control after 72 hours. No effects (relative size differences, unusual cell shapes, colours, flocculations, adherence of cells to test containers, or aggregation of cells) were noted during the test. Exposure of algae to the test material for 72 hours resulted in a median effective concentration (EC50) of 1.4 mg/L (95 % confidence interval = 1.2 to 1.6 mg/L) when determined using the number of cells/mL, and 2.9 mg/L (95 % confidence interval = 2.6 to 3.2 mg/L) when determined using the average specific growth rate. When treatment data are compared to the controls, the 72 hour NOEC is 0.59 mg/L when determined using the number of cells/mL or the average specific growth rate.