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Ecotoxicological information

Toxicity to soil microorganisms

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Incubation of soil for 28 days with nominal concentrations of Cereclor S52 (52% chlorinated) at up to 400 mg/kg dry wt soil had no effect on the extent of transformation of soil nitrogen to nitrate. The NOEC is 400 mg/kg dry wt of soil in this test system.

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In a GLP study conducted according to OECD guideline 216, the effect of Cereclor S52 (a C14-17 chlorinated paraffin; 52% chlorination) at 25, 50, 100, 200 and 400 mg/kg dry wt soil (nominal concentration) on the transformation by soil microorganisms of an organic nitrogen source (lucerne) to nitrate over a period of 28 days has been assessed. Nitrapyrin, a substance known to inhibit nitrogen transformation, was found to decrease nitrate formation by 35 and 29% when present at concentrations of 3.2 and 20 mg/kg dry wt of soil, respectively.

No statistically significant decrease in nitrate formation was seen at any concentration of Cereclor S52, indicating that the no-observed-effect concentration (NOEC) in this test is 400 mg/kg dry wt of soil. Based on the default soil characteristics used in the TGD, this NOEC is equivalent to 500 mg/kg dry wt, which when adjusted for a soil organic carbon content of 2%, is equivalent to 440 mg/kg wet wt (Thompson, 2002).