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Ecotoxicological information

Toxicity to terrestrial plants

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Description of key information

No reliable toxicity data were available for terrestrial plants. Hence, no toxicity data could be put forward for this type of soil organisms for the derivation of a terrestrial PNEC.

Key value for chemical safety assessment

Additional information

A limited amount of data on the effect of barium exposure to plants have been identified, but none of the data were useful for risk assessment purposes.

 

Barium in the environment is mainly present in forms with low solubility (as sulfate or carbonate), and therefore the risk of barium ecotoxicity is considered to be very low. Phytotoxicity of barium seems to be relatively low, although few investigations have addressed critical toxicity concentrations for barium in soils and plants. Unfortunately, no data on internal toxic barium concentrations in relation to clearly established substrate Ba-levels are available. The lack of such information hampers the evaluation of the environmental risk of ambient Ba (Llugany et al, 2000).

 

In a first study Llugany et al (2000) exposed freshly germinated bush beans seeds (Phaseolus vulgaris) to several Ba-levels in solution (total Ba exposure time 48h; total treatment time 96h). Exposure to 50µM barium had no negative effect on plant growth. Barium concentrations of 500 M or higher were clearly toxic to the bean plants. After only 24 h exposure to 5,000 M Ba, the primary leaves of some plants exhibited withered areas, and wilted primary leaves were observed after 48 h exposure to barium. Secondary root elongation was the growth parameter most sensitive to Ba and was completely inhibited by 500 M barium. The primary root was more Ba-tolerant, and a severe elongation inhibition was only observed in the 5,000 M barium treatment. This treatment also caused a significant reduction of the root and shoot dry weight. The dry weight of the developing trifoliate leaves was most severely decreased, but the primary leaves that had achieved maximum expansion before the start of the barium treatment were hardly affected. Data, however, are not useful for PNEC-derivation; the authors themselves stated “that these results from nutrient solution studies are not directly extrapolable to the field”.

 

In another study, Carter and Wain (1964) reported on the toxicity of barium to wheat (species not specified), but here too exposure occurred via the water phase (i.e., Ba-concentration in solution). A nominal EC50of 1.72 g/L (12.5 mmol) was reported (endpoint: root growth).

 

The third study that reported on Ba-toxicity in solution for plants was described in Suwa et al (2008). Barium (Ba)-induced phytotoxicity at 100, 1000, or 5000 μM Ba (13.7, 137 and 687 mg/L, respectively) in soybean plants (Glycine max) was investigated under hydroponic culture conditions. Soybean growth and leaf photosynthetic activity were significantly inhibited by all three levels of barium treatments.