α,α,α,4-tetrachlorotoluene

Short-term toxicity to aquatic invertebrates

Description of key information

EC50 > 100 mg/l, nominal concentration

Additional information

Two studies on short-term toxicity to aquatic invertebrates are available.

In the key study, the acute toxicity of the test item to Daphnia magna was determined in a 48‑hour static test according to the OECD Guideline 202 (2004). No analitical monitoring was however performed during test.

For this purpose, juvenile daphnids (< 24 hours old at initiation of the test) were exposed to an aqueous test medium containing the test item at the only nominal concentration of 100.0 mg/L. The exposed organisms were checked for immobilization 24 and 48 hours after test initiation.

The pH of the control (test medium without test item) was 7.13 and the pH of test item solution immediately after preparation was 7.03, therefore, the pH of the test medium was not adjusted before the start of the test.

The room temperature was in the range 21.2 °C during the test period, according to the OECD’s recommended range (20 ± 2°C).

Light intensity during the 48 hours of test period was in the range 368-401 Lux, within the range 200-1500 Lux.

At the end of test period, in the negative control no immobilization was observed and no daphnid was found trapped on the test water surface. These values comply with the specified validity criterion that immobilization in the negative control group should not exceed 10% at the end of the test.

No immobilization was observed in the test item medium after 24 and 48 hours, therefore the NOEC (highest concentration tested without toxic effects after the exposure period) was determined to be equal to the nominal tested concentration of 100.0 mg/L.

Based on the observed effects, the LOEC and the 48-h IC₅₀were determined to be greater than the tested concentration, 100.0 mg/L.

In the supporting study, the authors assessed the acute toxicity of p-chlorobenzotrichloride to Daphnia magna Straus (Crustacea) in a static system. The test was performed according to DIN 38 412 Part 11, which is similar to the OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test). The test organisms were exposed for 24h to six different concentrations of p-chlorobenzotrichloride (i.e. 8.31; 83.1; 103.9; 166.3; 415.7; 831.4 mg/L) and a negative as well as a reference control (i.e. potassium dichromate; 2.0 mg/l) was included. For each condition, two replicates, each containing 10 dapnids between 3 and 24h, old were used.

Under the test conditions an EC50 (24h) was reported of 209.9 mg/L with a 95% confidence interval ranging from 188.4 to 417.4 mg/L and the negative and reference control gave the expected results.

Although the statistical analysis used results in a EC50-value with a large 95% confidence interval, it is likely that performing the test according to the OECD guideline 202 (meaning 48h of exposure and analysis with appropriate statistical methods such as probit analysis) would also give a EC50-value above 100 mg/L but less than this observed value.