Boron

Toxicity to soil macroorganisms except arthropods

Description of key information

In total 24 individual high-quality NOEC/EC10 values (for five different species) are selected for the PNEC derivation, ranging from 5.2 mg B/kg dw for Eisenia andrei growth to 315 mg B/kg for Eisenia andrei survival (Stantec Consulting & Aquaterra Environmental Consulting, 2003). Ecotoxicity reference values of the five species ranged from 17.0 mg B/kg soil dw for E.luxuriosus to 70.1 mg B/kg soil dw for E.fetida.

Data (EC10, NOECs) were generated in single-species toxicity tests with invertebrates, and are based on added nominal values because background concentrations are not always available, and the added risk approach is followed because of the significant difference in bioavailability between boron naturally present in soils and added soluble B.

Additional information

The identified reliable long-term data for the soil invertebrate species were used for the determination of a PNEC for the terrestrial compartment, using the statistical extrapolation method. All reported effect levels were generated with boric acid as test substance. The reference values for the enchytraeids E. fetida and E.andrei represent the geometric mean of several tests that assessed reproduction and growth, respectively, as effect criterion. All other values represent the outcome of an individual study that was conducted with the respective species.

 

Boric acid and borates have been registered as pesticides effective against a number of terrestrial insects, for example cockroaches, termites and ants. However the studies that establish efficacy as a pesticide are not relevant for use in describing ecotoxicological responses from boron present in soil because these pesticide studies typically involve use of a specially formulated diet or bait or treated article.

For example, Durmuş and Büyükgüzel (2008) reported effects on survival and development of larvae of the Greater Wax Moth, Galleria mellonella, when fed artificial diets containing 0.2 % sodium tetraborate. No effects were observed when fed 0.1 % sodium tetraborate. Yang et al. (2000) reported reduction in survival and reproduction of the Caribbean fruit fly Anastrepha suspensa when fed 0.1 to 0.5 % sodium tetraborate. Since the diets were not soil-based (as might occur for an earthworm), such studies cannot be relied upon for derivation of a PNECsoil. The critical boron concentrations in food (approx. 0.1 % or 1000 mg B/kg) are orders of magnitude above the soil effects concentrations of boron for invertebrates (5-300 mg B/kg). Because boron does not magnify through the food-chain and soil to plant bioaccumulation factors for boron derived from tests performed in real soils are generally < 100 and internal boron concentrations in plants are largely controlled by plant-specific requirements for this essential element, it can be concluded that the secondary poisoning of insects through plant material is not critical for boron.

 

All NOEC or EC10 values (including selected, non-selected, unbounded and rejected values) and their corresponding robust study summaries are summarized in Appendix F from the “Boron effects assessment in the terrestrial compartment” report. Further additional information on boron toxicity to the terrestrial compartment can also be found in the Background Document “Environmental effects assessment of boron”, which is attached in the technical dossier in IUCLID Section 13.