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Ecotoxicological information

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Several studies are available on the chronic effect of arsenic to soil organisms, including microorganisms, plants, invertebrates, mammals and birds.

Available NOEC values for soil biological function cover respiration and mineralization and range from 63 mg/kg to 100 mg/kg. However, none of the identified studies is considered reliable. Based on a weight of evidence approach and an assessment of available data, the lowest reported NOEC value is the 14-wk NOEC of 63 mg/kg dw (added As) for soil respiration and N mineralization and nitrification based on Speir et al. (1992).

NOEC/EC10 values are also available for the growth of mono- and dicotyledonous plant species ranging from 10 mg/kg dw to 69.5 mg/kg dw. However, none of the identified studies is considered reliable. Based on a weight of evidence approach and an assessment of available data, the lowest reported NOEC/EC10 value is the 4-wk EC10 of 10 mg/kg dw (added As) for the growth of Zea mays based on a study by Woolson et al. (1971).

Several reliable NOEC values are available for different invertebrate species, including collembolas, enchytraeids and earthworms and ranging from 5 mg/kg dw to 10 mg/kg dw. The lowest reported NOEC value is the 4-wk NOEC of 5 mg/kg dw (added As) for the reproduction of Folsomia candida based on a study by Lock and Janssen (2002). This NOEC value can be considered conservative as the toxicity of arsenic was assessed in a freshly spiked artificial OECD substrate assuming that bioavailability and subsequent toxicity are lower in natural soils (see read-across approach).

In sum, soil invertebrates appear to be most sensitive, and the lowest reported NOEC value of 5 mg/kg dw (added As) for the reproduction of Folsomia candida (Lock and Janssen, 2002) is considered for the Chemicals Safety Assessment.