Metals, their Biological Functions and Harmful Impacts - Mining and the Environment: From Ore to Metal - page 475

11

Metals, their Biological
Functions and Harmful
Impacts

Metals are Naturally Occurring
Elements

In chemistry we learn that all known matter is made up of 109 known elements (not
all of them are naturally occurring). Elements are the most basic substances consisting
of atoms arranged in characteristic structures. An element cannot be broken down
by chemical means into anything simpler. Elements are further subdivided into metals
and nonmetals. Interestingly, most known elements are metals (86 in total) but over
80% of the Earth's crust, the area of interest for the mining industry, is made up
of nonmetals. On the periodic table, metals are all the elements to the left of the
diagonal line running from boron to astatine ( Figure 11.1 ).

Chapter Eleven offers a brief discussion of some of these metals, their biological functions
and harmful impacts. It does appear that increased global concern about the state of the envi-
ronment has led to over-emphasizing the harmful impacts of metals and certainly to down-
play their benei ts. This may be related to the unfavourable views of society towards mining.
Metals are naturally occurring elements, and life has evolved in their presence.
Industrial activities and human use of metals have liberated, transformed and accumulated
metals in some geographic areas and for some metals such as lead or mercury, changes
in concentrations can be detected on a global scale. It is also true that on occasions these
human activities have caused harm for public health and the environment (USEPA 1995;
MMSD 2001). Metals which are of most environmental concern include arsenic, cadmium,
chromium, lead and mercury (listed in alphabetic order). However, the fact that methyl
mercury is a serious threat to life does not support claims that mercury in all forms and
concentrations is equally harmful. Similarly, while exposure to lead can result in poisoning

Metals are naturally occurring
elements, and life has evolved in
their presence.