| Summary: | Numerous applications of heavy metal have caused to their wide contamination in the environmental system and raised serious concerns over potential harmful effects on public health and the environment. Water, sediment, and dietary food are the main exposure media of heavy metal pollution and key determinants of adverse human and environmental health effects. Heavy metal(s) toxicity and speciation involve various mechanistic features with specific media and some of them are not clearly investigated. In particular, biological effects such as toxicity are not related to the total concentration of heavy metals in media, and many laboratory and field studies have supported this supposition. Organisms respond to the bioaccessible and bioavailable fraction of metals only, not the total concentration. The bioaccessibility and bioavailability of toxicants are dependent on chemical properties of the contaminant, the many exposure pathways, and temporal variability of these variables with respect to uptake by the target organism. Usually, bioavailable fractions are estimated using chemical or biological approaches. For this study, biological approaches were performed to better ascertain the toxic effects of heavy metals on organisms. A better understanding of bioaccessibility and bioavailability can be a useful tool in exposure and risk assessment. Therefore, this study presents experimental designs focusing on assessing of the bioaccessibility and bioavailability of metals in aquatic, benthic organisms and dietary food. This study also examines the role of metal mixtures on the adverse effects of metals.
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