The Webweavers: Last modified Tue, 20 Jul 2005 10:02:51 GMT
of surface freshwaters. Any use of residential, industrial or
agricultural land will have an impact on the quality of surface freshwaters
and groundwaters. Since water is essential for all forms of life, quality
standards for the use of freshwater supplies are strictly defined by official
regulations. Drinking water must be free of toxic chemicals and pathogens
which are to be eliminated by standard water treatment facilities.
quality water, which cannot enter the urban water distribution system, may be
used, depending on the contamination level, in agriculture or industry, or can
be classified as toxic waste which requires a special means of disposal.
Toxic heavy metals can be released from specific
production processes: for example,
chromium is released from tannery activities, cadmium from foundry
waste, lead from the paint industry. Finally, toxic
can be released
into the environment, and their different degrees of chemical and biological
degradability may cause damage to living organisms.
Examples of toxic organic chemicals found in freshwaters are pesticides used
in agriculture, and detergents or surfactants, easily recognised by their
characteristic foam. Some of these surfactants have been seen to mimic typical oestrogen
activity on humans with the result, in the case of drinking water, of an
increase in testicular and breast cancer and a
decrease in the number of spermatozoa.
Fig. 2: Polluted river in U.K.
(Credit: Ben Osbome)
Indoor pollution. Confined spaces such as houses, offices and other enclosed
workplaces are characterised by important types of chemical and biological
Biological pollution refers to the presence of fungi, molds,
spores, bacteria and viruses, which are examples of indoor biological
pollutants. These find an ideal habitat in
houses – in suspended particulate matter, house dust (host to mites and other
species responsible for asthma attacks), pets, poorly maintained air
conditioners and damp walls. Common health effects are allergies and other
reactions of the immune system which lead to asthma, dermatitis, etc.
Added to this we can mention chemical pollution, which includes: (i)
combustion products from badly-ventilated or malfunctioning heating
appliances, cooking stoves and tobacco smoke, (ii)
volatile organic compounds
from pressed wood products, wallpaper and
common household products (hair spray, glue, cleaning agents, pesticides, etc.).
Adequate ventilation is an effective way
to maintain good indoor air quality, although
it does allow outdoor air pollutants to enter.
Finally, a radioactive natural gas,
(a member of the uranium family which can cause cancer) completes the
list of potential indoor pollutants.
Because of its gaseous nature, radon,
emitted from particular types of rocks and soil, groundwater or earth-derived
construction materials, can easily infiltrate any buildings which may be above
Toxic and carcinogenic
substances from passive smoking indoors.
| Fig. 4:
Coatings and paint on walls
and furniture, etc. release over time various
volatile organic compounds (formaldehyde, solvents, etc.).
Emission of organic substances (lipids and their oxidation products) from