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Volatile organic compounds, e.g. Polycyclic
aromatic hydrocarbons (PAH?s)
Because of their widespread use in fuels hydrocarbons
predominate among organic atmospheric pollution.
Unsaturated compounds such as PAH's are generally the
result of the incomplete burning process. Being
unsaturated these compounds are often more reactive
and are associated with the formation of "photochemical"
smog. Many compounds exhibit a carcinogenic ability.
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Inorganic Fluorine & Chlorine compounds
Fluorine, hydrogen fluoride and other volatile fluorides
are produced during the manufacture of Aluminium and
phosphate fertilisers where they are found in the
minerals from which these are mined. Hydrogen fluoride
gas is dangerously toxic, irritating to body tissues and
at the parts per thousand level may be fatal. Exposure
to fluorides can cause fluorosis. Plants are particularly
susceptible to the effects of gaseous fluorides.
Chlorine was the first poisonous gas deployed in the 1st
World War. It is used as a manufacturing chemical in the
plastics industry and in water treatment. Incineration
of chlorinated plastics releases hydrogen chloride,
which rapidly dissolves in water vapour as hydrochloric
acid.
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Organic oxides
Such as ethylene and propylene oxide, used as
intermediaries in the chemical industry and also as a
fumigant and sterilant. Although only a limited
potential to enter the environment these are known
mutagen* and carcinogens.
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Organohalides (carbon based compounds containing
fluorine, chlorine, bromine or iodine)
These are widely used in industry, e.g. Di-chloromethane
used in paint stripper, as a blowing agent in urethane
polymer manufacture, Dichlorodifluoromethane used as a
refrigerant, Vinyl chloride used in manufacture of pipe,
hose and other PVC products. Poly chlorinated Bi-phenyls
used as heat transfer and hydraulic fluids.
Many of these compounds are known to have carcinogenic,
mutagenic and teratogenic* properties and as they
are generally difficult to break down build up in the
food chain and in the environment.
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Organo nitrogen compounds, e.g. aniline
Contaminants in this category include amines, amides,
nitriles, nitro compounds, or heterocyclic nitrogen.
Amines have a rotten fish odour an obvious reason why
air contamination by this group is undesirable. Aniline,
pyridine and naphthalenes are used in the manufacture
of dyes, amides, photographic chemicals, drugs,
pesticides, pigments, and curing agents. This group is
of particular concern in the workplace as well as the
general atmosphere as they are among some of the few
chemicals whose carcinogenic behavior has been based
on observations of humans.
* (Mutagen: alters DNA to produce inheritable traits,
can therefore cause birth defects).
* (Teratogen:
Materials classed as teratogenic, can kill the embryo or
fetus or cause other damaging changes that can
result in metal retardation, deformed organs or other
birth defects. In males damage may occur to sperm
chromosomes.)
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