Hazard Identification and Assessment

Hazard identification is a central part in the process of evaluating the safety of a metallic or any other chemical compound. Such identification evaluates the totality of information about chemical and toxicological properties. It is important to consider different metal compounds (species) separately when evaluating metabolism, toxicokinetics, and effects. The basis for classifying toxicological properties are adverse effects observed in humans, in animals, in in vitro systems, and as modeled by computational tools. Information about chemical and toxicological properties allows the classification of substances as persistent, bioaccumulative, toxic, corrosive or irritating to the skin or mucous membranes of the respiratory or gastrointestinal tract; sensitizing to the skin or respiratory tract; toxic to reproduction and development; and mutagenic or carcinogenic. The hazard identification process characterizes the weight of evidence for causation of specific adverse effects as sufficient, limited, or insufficient. Concerning induction of effects in humans, human data are of great importance and data from animals or in vitro systems are also valuable. The mechanism of action or the mode of action, when known, provides additional support. Sometimes it is possible to describe an adverse outcome pathway. Based on all available information, a systematic analysis leads to a grading of the weight of evidence supporting that the chemical compound causes the adverse effect under consideration. Human exposures known or predicted to occur form the basis for the assessments. It is important to follow applicable ethical and legal rules when performing studies involving human subjects or animals.