Page 93 - Soil and water contamination, 2nd edition

80 Soil and Water Contamination

• amosite, or brown ( amphibole) asbestos, also called cummingtonite/grunerite:

Fe Si O (OH)
7 8 22 2
3+
2+

• crocidolite, or blue (amphibole) asbestos, also called riebeckite: Na Fe Fe Si O (OH)
2 3 2 8 22 2
• tremolite: Ca Mg Si O (OH)
2 5 8 22 2
• actinolite: Ca (Mg, Fe) (Si O )(OH)
2 5 8 22 2
• anthophyllite: (Mg, Fe) Si O (OH) .
7 8 22 2
Asbestos minerals are chemically inert and have a high tensile strength. They can be woven,
are resistant to heat and fire and do not conduct electricity. Because of these properties,
asbestos has been used in a variety of industrial products and commercial goods, including
roofing shingles, ceiling and floor tiles, coatings, electrical insulation wire, textiles, and
automobile brakes and clutches.
In its natural form, asbestos is known to be a non-toxic, harmless material. Its health
hazard to humans is associated with its fibrous nature. When asbestos fibres become airborne,
they can be inhaled deep into the lungs. Prolonged inhalation of asbestos fibres can cause a
build-up of scar-like tissue in the lungs called asbestosis, which often results in loss of lung
function that may progress to disability or death. Asbestos may also cause lung cancer or other
diseases such as mesothelioma, a rare form of cancer that develops in the membrane lining of
many of the internal organs. Although the amphibole asbestos types (amosite and crocidolite)
are considered to be the most hazardous, exposure to all types of asbestos fibres is known to
be a serious health hazard in humans. Heavy exposure tends to occur in asbestos mining, the
construction industry and in ship repair, particularly during the removal of asbestos materials
due to renovation, repairs, or demolition. In general, the greater the exposure to asbestos, the
greater the chance of developing harmful health effects, but disease symptoms may take several
years to develop. The European Union and Australia have banned all use of asbestos and
extraction, manufacture and processing of asbestos products. In the United States, however,
many consumer products may still legally contain trace amounts of asbestos.
Although human exposure to asbestos is mostly associated with indoor environments
and construction sites where old material containing asbestos is present or is being processed,
soil contaminated by asbestos may also pose a threat to human health. Abandoned industrial
premises and former waste disposal sites are particularly likely to be contaminated by
asbestos. At such sites, asbestos may be typically found on the surface or buried at shallow
depth. Asbestos fibres in soil are not inherently hazardous to humans when left undisturbed.
However, asbestos in soil may become airborne as a result of intense activity like digging,
ploughing or vehicle movement. The fibres tend to be released more readily into the air
from dry, coarse-grained, well-drained soil. Fibres are particularly likely to become airborne
if the asbestos is present in the form of high concentrations of friable material. In general,
hazardous concentrations of airborne asbestos fibres only occur in a limited radius (about
100 m) around the point of activity.

4.2.5 Nanomaterials

As noted in section 4.1, nanomaterials are particles ranging from 1 nm to 100 nm in size,
and comprise nanoparticles, nanotubes, nanocapsules, and nanofibres. As a result of their
extremely small sizes, nanomaterials have a large surface to volume ratio and their surface
chemistry differs from that of their parent compounds. They also have distinctive optical
and electronic properties. Based on their composition, they can be classified into carbon-
based materials, metal-based materials, dendrimers and composites. As their name implies,
carbon-based nanomaterials are composed mostly of carbon, usually taking the form of
a hollow sphere, ellipsoid, or tube. Spherical and ellipsoidal carbon nanomaterials are
called fullerenes, whereas cylindrical carbon nanomaterials are called nanotubes. Spherical

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