| Abstract |
Inorganic metals and metal compounds have unique characteristics that should be considered when assessing their risks. Some of these characteristics typically are not considered when assessing the risks of organic substances. For example, metals are neither created nor destroyed by biological or chemical processes; they are transformed from one chemical form to another. Native (zero valence) forms of most metals and some metal compounds are not readily soluble, and as a result, toxicity tests based on soluble salts may overestimate the bioavailability and toxicity of these substances. Some metals (e.g., copper (Cu), selenium (Se), and zinc(Zn)) are nutritionally essential elements at low levels but toxic at higher levels, and others (e.g., lead (Pb), arsenic (As), and mercury (Hg)) have no known biological functions. Because metals are naturally occurring, many organisms have evolved mechanisms to regulate accumulations, especially accumulations of essential metals. This metals risk assessment Framework identifies metals principles that are fundamental truths (or properties) of metals. The metals principles should be addressed and incorporated into inorganic metals risk assessments. |
