Minerals - The Ecology of Building Materials - page 72

Table 6.2: Potential pollution in the production phase

Metals Boiling point (°C) Potential process pollution

Cast iron up to 3000 SO 2 , CO 2 , dust, Ar (when smelting scrap iron)

Steel 1535 Pb, Hg, Cd

Aluminium 2057 PAH, Al, F, CO 2 , SO 2 , dust

Chrome 2200 Cr

Cadmium 767 Cd, SO 2

Nickel 2900 Ni, SO 2

Zinc 907 Pb, Hg, Cd, SO 2

Lead 1620 Pb, Cd, SO 2

Copper 2310 SO 2 , Cd

Zincing Cr, Fl, phosphates, cyanides, organic solvents

Galvanizing Cr, Fl, phosphates, cyanides, organic solvents

Note: The boiling point indicates the risk of vapourizing during different processes, such as when making
alloys

The usage cycle of metals in buildings causes relatively few environmental prob-
lems, except for particles that are washed off the surface when exposed to different
weather conditions. Lead roofing and flashings and metallic salts used in the
impregnation of timber can lead to the
pollution of local wells or soil. Large
amounts of metal, as in reinforcement
for example, can lead to a stronger
electromagnetic field in the building.
In waste products, metals that are
exposed to running water release
metallic particles into soil and water
which can damage many different
organisms, depending upon the
amount and degree of poison con-
tained in them. It is important to note
that pollution due to metals is irre-
versible. Metals left in the natural
environment will always be there -
they do not decompose. Even if the
amount of metals released is reduced,
the total amount of metals ending up
in the environment will still be
increasing. The possibilities of recy-
cling metals, however good, only
postpone the inevitable pollution.

Figure 6.1: Heavy extraction of minerals can cause damage and
destroy the local biotopes and the quality of the groundwater.