API PUBL 4666-1999

$30.55

The Toxicity of Common Ions to Freshwater and Marine Organisms

Published By	Publication Date	Number of Pages
API	1999	112

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Description

Whole effluent toxicity (WET) tests have become a common tool in the evaluation of effluent for discharge acceptability. The majority of toxicants identified in effluents are either inorganic trace metals (e.g., cadmium, copper, etc.) or organic compounds (e.g., diazinon, surfactants). Others, however, are inorganic ions that nearly always are present in most aquatic systems and, in most cases, are present at nontoxic concentrations. These ions include bicarbonate, calcium, chloride, magnesium, potassium, sodium, sulfate, and others. Recent investigations have indicated that, in certain effluents, deficiencies or excesses of these "common" ions can cause significant acute or chronic toxicity in WET tests. This report presents the results of a review of toxicological and physiological data on inorganic ions that have been implicated in causing significant toxicity.

The scientific literature was searched for freshwater and marine toxicity data on bicarbonate (HCO₃), borate (B₄O₇^2-), bromide (Br^–), calcium (Ca²⁺), chloride (Cl^–), fluoride (F ^–), magnesium (Mg²⁺), potassium (K⁺), strontium (Sr²⁺), and sulfate (SO₄^2-). A review also was completed on the roles that several common ions play in normal physiological functions and the impacts of abnormal levels of these ions. All states and EPA regions were surveyed to determine what, if any, guidelines currently are in place to address the question of common ion toxicity.

The impact of aberrant levels of ions differs markedly with the ion in question as well as the organism being tested. Some ions, Ca²⁺ and K⁺ for example, cause significant acute toxicity when they are deficient in the exposure media, while other ions appear to have demonstrable effects only at excess levels. Whole effluent toxicity due to the common ions can pose a problem for some dischargers who must identify and/or eliminate toxicity in their effluent. This problem arises because standard Toxicity Identification Evaluation (TIE) manipulations often are ineffective in separating ion toxicity from other potential candidates. However, techniques such as mock effluent studies and computer models can be used in conjunction with traditional TIE methods to provide definitive identification of ion toxicity.

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