Environmental Engineering Reference
In-Depth Information
Table 3.6 Size of asbestos fibres revealed by measurements taken near an asbestos quarry in
Quebec [
32
]
Outdoor air MDDEP (Bisson and
Couture, 2007) (f/ml)
Indoor air AVAQ (Marier et al. 2007)
(PCMe fibres/ml)
Counting
criteria
L
5
m, D
3
m, and ratio L/D
L
5
m, D
0.25
m and
3
m
>
μ
<
μ
>
μ
μ
<
μ
3:1
and ratio L/D
3:1
>
>
Average
0.0029
0.0020
Minimum
0.00038
0.000553
Maximum
0.028
0.010
Upper limit of
95 % Cl
0.0035
0.0031
Concentrations vary from 6-22
μ
g/Nm
3
in indoor air to 28-96
μ
g/Nm
3
[
33
]
Once the use of asbestos in large-scale applications was limited because of its
proven cancer-causing characteristic, asbestos mining decreased considerably, but
did not stop. Consequently, in order to limit the danger of asbestosis and lung
cancer, numerous studies have been carried out to establish strict and coherent rules
for asbestos exploitation [
31
-
34
].
As shown in Fig.
3.6
, asbestos fibres can vary in size from 80-90 nm to 10
m.
As a result, they are considered potentially dangerous for any kind of living
cells [
33
].
Table
3.6
shows values of asbestos fibres measured inside and outside buildings
situated near an asbestos quarry in Quebec (Canada).
μ
3.2.3 Exploitation of Natural Construction Materials
Stone quarries and gravel pits are major sources of nanoparticle pollution, espe-
cially if stone crushers and/or sorting machines are used for sorting sand or crushed
material by grain size.
Most technological processes of rock removal (or extraction by water bed
dredging), transport (conveyor belts or trucks), grain sorting and storage take
place in open air, therefore wind carries away stone dust and fine sand particles.
In a stone quarry located near Harare (Zimbabwe), in a usual working month, the
level of PM expressed as respirable and inhalable PM varied with the distance from
the crusher and the stone sorting machine, as shown in Fig.
3.7
[
35
].
The PM amounts in the two categories represent maximum and minimum values
corresponding to discontinuous operations of unloading stone from the crusher. The
obvious general tendency is a concentration decrease with the distance from the
quarry machines. The smaller the particles are, the smaller the decreasing tendency
is. PM
4
and PM
2.5
emissions in a silica sand quarry in Arizona were measured
before and during plant operation with vibrating sieves [
36
]. The values exceeded
the limits established in US EPA, but this is a general issue of any plants operating
with particulate matter.
