Civil Engineering Reference
In-Depth Information
fi sh and birds, and because this volatile compound tends
to evaporate into the atmosphere rather than persist in
surface waters or soils. However, volatiles such as this
compound can pose a drinking water hazard when they
accumulate in ground water.
Acetone
- is another by-product of the combus-
tion of carbonaceous material. In small amounts the liver
breaks acetone down into chemicals that are not harmful
and uses them for everyday body functions. Breathing
moderate to high levels of acetone for short periods of
time (i.e. painting in a poorly ventilated area) can cause
nose, throat, lung and eye irritation, headaches, light-
headedness, confusion, nausea, vomiting and if the
exposure is for a long period, unconsciousness, coma
and death. It may damage the kidneys and liver.
It has slight short-term toxicity on aquatic life.
Acetone has caused membrane damage, a decrease in
size and a decrease in germination of various agricul-
tural and ornamental plants. It may also have slight long-
term toxicity to aquatic life. Chronic and acute effects on
birds or land animals have not been determined.
Polychlorinated biphenyls
- polychlorinated
biphenyls (PCBs) is the term for a group of compounds
used in the construction of electrical equipment. When
PCBs are involved in fi res that expose them to temper-
atures ranging from 500 to 700C, they form a variety
of other compounds. In fi res involving electrical PCB-
containing electrical equipment it is common for PCBs to
form a distribution of black carbonaceous soot. PCBs
have been identifi ed in soot following numerous electrical
equipment fi res and have been detected in soot samples
collected following transformer fi res. However, PCBs
are also released into the environment as a vapour,
for example when pressure relief valves of overheated
transformers operate. The pressurised release of hot PCB
vapours can entrain considerable quantities of liquid PCBs
forming a fi ne aerosol that can be distributed to areas
beyond the transformer air currents.
Exposure to PCBs can cause gastrointestinal distur-
bances and nerve damage. There is suggestive evidence
of associations between increased incidences of cancer
and exposure to PCBs. However, defi nite casual relation-
ships between exposure and carcinogenic effects are
unclear.
Fire fi ghting water/foam run-off
- obviously the
water used for fi ghting fi res is likely to be contaminated
to an extent with all of the above contaminants. In
addition, if the Fire and Rescue Service use foam to fi ght
a fi re, for example in a boiler room, the foam itself is likely
to contain perfl uorooctane sulfonate (PFOS).
PFOS is an organic compound which does not
break down in the environment, and that makes foam
spread rapidly at high temperatures, cutting the time it
takes to put out a fi re. It accumulates in organisms and
works its way up the food chain. It has been found to be
Figure 13.1
The environmental impact of fi re
Sulphur dioxide
- sulphur dioxide (SO
2
) is a colour-
less gas; it reacts on the surface of a variety of airborne
solid particles. It is soluble in water and can be oxidised
within airborne water droplets. The major health hazards
associated with exposure to high concentrations of
sulphur dioxide include affects on breathing, respiratory
illness, alterations in pulmonary defences and aggravation
of existing cardiovascular disease. In the atmosphere,
sulphur dioxide mixes with water vapour producing
sulphuric acid. This acidic pollution can be transported
by wind over many hundreds of miles, and when present
in suffi cient quantities can be deposited as acid rain.
Carbon monoxide
- carbon monoxide (CO) is an
odourless, colourless and toxic gas. It is a narcotic gas
that quickly induces sleep and because it is impossible
to see, taste or smell the fumes are particular danger-
ous. Exposure to CO can result in angina, impaired
vision and reduced brain function. At higher concentra-
tions, CO exposure can be fatal. While the direct effect
on the environment is minimal CO assists in the creation
of smog or ground level ozone.
Benzene
- is an aromatic hydrocarbon that is
produced by the burning of organic products such as
wood and other carbonaceous materials - it is also
produced in the decomposition of plastics. As an aromatic
hydrocarbon benzene contains high quantities of carbon
that are rarely fully burnt during combustion. This results
in unburnt carbon being released into the atmosphere,
which has the distinct appearance of thick black
smoke. Benzene is used in the manufacture of plastics,
detergents, pesticides and other chemicals. Short-term
exposure to high levels of benzene can cause drowsi-
ness, dizziness, unconsciousness and death. Benzene
is also known to be a carcinogen causing leukaemia and
affecting bone marrow and blood production.
Benzene is more frequently associated with risk to
humans than with risk to fi sh and wildlife. This is partly
because only very small amounts are absorbed by plants,
