Freshwater

Cadmium :: freshwaters ecosystems

Key concerns

The toxicity of cadmium to aquatic organisms is variable, and it depends on both the species and environmental factors such as water hardness, salinity, temperature, pH, organic matter content and the presence of other metal ions, especially calcium and zinc (WHO 1992). Toxicity to aquatic organisms generally increases with increasing temperature and decreasing salinity and hardness. Early life stages of organisms, especially embr yonic and larval stages, are more sensitive to the effects of cadmium than the adult stage.

Boron :: all ecosystems

Key concerns:

Boron toxicity in plants is most likely to occur following the continued use of boron-contaminated irrigation waters, however, direct exposure from airborne emissions may also produce localized toxic effects (Howe 1998). Symptoms of boron toxicity in plants include yellowing, spotting or drying of leaf tissues, especially on the tips and sides of older leaves (Gupta et al. 1985).

Antimony :: all ecosystems

Key Concerns:

There is a paucity of data on the effects of antimony on species and their ecosystems.

Emissions of antimony, such as those from smelters, can remain in the atmosphere for more than one month and therefore be transported over long distances (ATSDR 1992; Steinnes 1997). Antimony in soil is likely to be in the form of antimony sulphide, which is slightly soluble, and therefore potentially bioavailable.

By-products or contaminants :: freshwater ecosystems

Key Concerns:

PAHs are acutely toxic to aquatic organisms due to the formation of toxic metabolites. The PAHs which are most toxic to algae are benz(a)anthracene and benzo(a)pyrene, with EC50 values ranging from 1 to 29 µg/l and 5 to 15 µg/l, respectively (WHO 1998). Corresponding EC50 values for 3 ring PAHs range from 240 to 940 µg/l. Naphthalene is less toxic than other PAHs, with EC50 values in algae ranging from 2800 to 34 000 µg/l.

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