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Ecotoxicological information

Toxicity to birds

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Description of key information

Avian toxicity data are available for barium but not for sulfide. Based on the findings by Schwarzbach et al (2006) and Ridgeway and Karnofsky (1952), elevated Ba-concentrations of eggs may result in deformations of the feet. 

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Additional information

Sulfide:

As sulfide does not have a potential for bioconcentration/bioaccumulation, secondary poisoning is not relevant. Further, to examine secondary poisoning (or the lack thereof), mammalian data may be considered.

Barium:

Schwarzbach et al (2006) reported levels of trace elements including barium, chromium and mercury in eggs of the California Clapper Rail (Rallus longirostris obsoletus) collected at the San Francisco Bay (South Bay and North Bay) (period: 1992 at S-B and 1998 at N-B):

- Ba-levels in eggs collected at the South Bay ranged from <0.1 to 0.59 μg/g dw, with a mean of 0.34 μg/g; Ba-levels exceeded the detection limit of 0.1 μg/l in 36 of the 38 analysed eggs.

- Ba-levels in eggs collected at the North Bay ranged from <0.2 to 4.1 μg/g dw. Ba-levels exceeded the detection limit of 0.2 μg/l in 8 of the 9 analysed eggs. Further, three embryos with deformities of the feet were found, and these effects were associated with the highest Ba-levels, ranging from 2.2 to 4.1 μg/g.

The mean Ba-concentration of normal, late-stage embryos (n=12) was 0.41 μg/g (range: 0.20–0.59 μg/g), whereas the mean Ba-concentration of deformed, late-stage embryos (n=3) was 3.00 μg/g (range: 2.16–4.13 μg/g). The difference was significant, but it should be noted that similar, significant findings were also observed for other trace elements determined simultanously, i.e., aluminium, chromium, mercury and strontium. Non-deformed late-stage embryos had Ba-concentrations that were similar to the concentration range reported for Light-footed Clapper rails in southern California by Hui et al (2002). Mean Ba-levels of 1.28 and 0.51 μg/g were found in malpositioned and normal late-stage embryos, respectively. However, Ba-levels in eggs were not significantly associated with malpositioning of late-stage embryos. Schwarzbach et al (2006) pointed out that the concentration of Ba (and other trace elements that interact with Ca or phosphate metabolism) was somewhat dependent on the stage of embryo development, with later stages having higher concentrations of these elements. Mobilization of Ba from the shell during embryo development seems likely, because the embryo extracts minerals from the shell for the developing skeleton (Tuan, 1987).

Malformation of the feet was also noted by Ridgway and Karnofsky (1952), who injected barium (as BaCl2) directly into the yolk of 4d or 8d old eggs, or onto the chorioallantoic membrane (CAM). Malformation of the toes occurred irregularly, but was seen in about 50 % of the treated embryos (8d old injection of yolk or CAM administration) that survived to 18 days. None of the embryos injected at 4 days showed toe abnormalities, and no other gross effects were noted on the embryo. However, the direct injection into the yolk or onto the CAM are not relevant uptake routes. The LD50for 4d-old eggs ‘injection in the yolk is >20 mg/egg. For 8d-old egg and administration via the CAM, the LD50values amount to approximately 11 and 0.8 mg/egg, respectively.

Malformation of the feet has not been observed for the other elements significantly elevated in deformed embryos. This may suggest that Ba was responsible for some of the observed malformations in the eggs collected at North Bay (Schwarzbach et al, 2006).