Human Health and the Environment 5

Human Health and the Environment 5 - H uman Health and the...

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Human Health and the Environment Lecture 5: Heavy Metals and Human Health Heavy Metals We say that heavy metals are all elements that have metallic characteristics but they also have a very high atomic weight – number one definition is based on atomic weight The second definition says that it is based on the density of the element – density of elemental forms of these metal They say that all elements that have density higher than 7g/cm3 belong to this group Some other scientists say that this is not true – we are going to base this definition on a specific gravity We actually don’t know or don’t agree with what heavy metals are and not only that Some elements known as metalloids (not really truly metals) Arsenic is it doesn’t have full characteristics but we still consider arsenic as a heavy metal There is another term that is very often used and seen in literature; this is known as trace elements It is different than metals – trace elements can be any element found in environment of lower concentration (very low sometimes hard to detect) For us here in our class and for most of the people heavy metals are toxic – only elements that are toxic based on their toxicity Where can we find them? They are coming from the ground – part of normal geological ground core of the planet We humans extract them as ore and mine them as ore and then extract them from the ore in different forms sometimes in a pure form or sometimes as a salt and incorporate them as different kinds of products After that, when we mine them, use them for some products, that product will finish their life cycle and possibly can be reused or can be deposited if some depositions occur again under the ground This closed circle of metals – before metal finished circle it is very widely spread everywhere in water, environment, food, air Most of them are toxic especially in some certain concentrations because every metal is toxic in some concentration (some of them in extremely low concentrations) They affect different types of organs and accumulate in certain parts of our body – selected tissues Life Support EESA10H3 S
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Classification of metals There are 3 basic groupings of the metals First is class A – not very toxic, low toxicity (i.e. K, Na, Mg, ,Ca, Al), are essential elements for plants, for us, they contribute to many physiological processes in our body and they are needed in significant amounts (that is why we call them macronutrients) and are essential These elements tend to form ionic bond; are usually positively charged Other class is class B – is very toxic (i.e. Hg, Ti, Pb, Ag, Au), these elements are not essential (we don’t need them for any process in our body), they just can interfere with the processes in our body and cause some adverse effects They have high electron negativity (opposite from class A), tendency to acquire electrons, form a covalent bond (form pairs of electrons)
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Human Health and the Environment 5 - H uman Health and the...

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