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Ecotoxicological information

Toxicity to terrestrial plants

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Description of key information

Non-standard experimental data, risk assessment (PNEC derivation) bases on aquatic data and EPM 

Key value for chemical safety assessment

Short-term EC50 or LC50 for terrestrial plants:
52.7 mg/kg soil dw

Additional information

No experimental guideline study data on effects to terrestrial plants are available. Testing for short-term toxicity to plants, required in Annex IX, column 1, section 9.4.3 has been waived in accordance with column 2 restrictions.

In the literature three short-term laboratory studies were identified, which give some evidence for biological effects using several experimental settings. The submission item exhibited retarding effects on biological functions of plant tissues.

First, it seems to increase the photosynthesis rate of radish (Raphanus sativus) leaf discs measured after 3 days incubation in the dark (Jordanov & Karanov 1977). This could be regarded beneficial or nontoxic. Nonetheless chlorophyll destruction during longer darkness is a normal physiological function of leaf tissues and thus the higher photosynthesis rate after re-illumination is a result of an inhibited physiological function, i.e. the chlorophyll destruction in absence of sufficient light. The inhibitory effect was present at a concentration of 0.1 mM test item in the aqueous exposure solution, which corresponds according to EPM (same calculation procedure as described in the section on “Toxicity to soil macroorganisms except arthropods”) to EC50 < 5.3 mg/kg soil dw.

Second the study of Karanov, Vasilev and Pogoncheva (1975) gives evidence for the inhibitory effect of the submission item to physiological chlorophyll destruction of radish leaves kept in the dark. After 4 days without any light stimuli in aqueous solutions of the test item more than 50 % impairment of the chlorophyll metabolism was visible however the dose response relation was poor. As the data suggest two overlapping mechanisms, the chlorophyll destruction metabolism EC50 is however assigned to < 0.0527 mg/kg soil dw (or < 52.7 µg/kg soil dw). Beside these sublethal effects the phytotoxicity NOEC to plant leaves was found ≥ 1852 mg/L (i.e. the highest concentration tested) or converted with the EPM ≥ 527 mg/kg soil dw.

Third, the results of the study of Karanov, Vasilev and Hristova (1975) on growth retarding effects of the submission item to peas (Pisum sativum) were not be finally assessed as the method publication (Knight et al. 1975) was not evaluated. The data suggest phytotoxicity NOEC ≥ 158.2 mg/kg soil dw, sublethal NOEC ≥ 0.527 mg/kg soil dw, and sublethal EC50 ca. 52.7 mg/kg soil dw of DMI to peas were found.

In conclusion there is evidence that the submission item potentially can cause impairment of terrestrial higher plant growth regulation physiology. The available data suggest a short-term NOEC of ca. 527 µg/kg soil dw and a EC50 of ca. 52.7 mg/kg soil dw on the basis of biochemical effects to radish. As the data suggest -however at high concentrations- some specific mode of action related to the photosynthesis apparatus of higher terrestrial plants, the aquatic effects were assessed in Duckweed (aquatic higher plant) rather than algae in order to get more evidence on the relevance of the literature data.

  • Knight BE, Taylor HF, Wain LR (1969). Ann Appl Biol 63:211