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microsoftinternetexplorer4
((foundations
of medicine))
air pollution
social
& economic aspects of air pollution:
these comprise:
a. destruction of plant and animal life.
b. corrosion of metals.
c. damage to buildings.
d. cost of cleaning, maintenance and repairs nuisance.
e. air pollution also reduces visibility in towns.
f. it can soil and damage clothings.
major
air pollutants:
ozone, o3 :
ozone is a gas, at ground level it is a hazard (bad ozone), however, in
stratosphere it serves to absorb some of potentially harmful ultra-violet (uv)
radiation from the sun, which is believed to cause skin cancer, among other
things (good ozone) sources o3 is not emitted into the atmosphere. o3is formed from o3 precursors, volatile organic compounds and
nitrogen oxides.
bad ozone effects:
¨ diverse effects on human health.
¨ ecological effects: damage vegetables and trees.
major nitrogen containing compounds:
n2 is a dominant gas of the
atmosphere 78% by volume. nox (nitrogen oxides) are formed from n2and o2 during high temperature combustion of fuel in cars.
noxeffects:
¨ 
cause the reddish-brown haze in city air which contribute to
heart and lung problems and may be carcinogenic.
¨ nox is an acid precursor which is a source of acid
rain when: nox + h2so4? hno3
¨ nox are the precursor of nitrate particulates.
¨ nox are major contributors to the formation of ground
level bad ozone.
major sulfur containing compounds:
sulfur dioxide so2 is a
colorless gas with a sharp odor, primary pollutant has anthropogenic (man-made)
and natural sources.
sulfur is present in many fuels e.g. coal
& crude oil over a wide range of concentration. combustion causes its
oxidation to sulfur dioxide.
so2 effects:
· 
at a relatively high concentrations so2 causes severe
respiratory problems.
· so2 is an acid precursor, which is a source of acid
rain produced when so2 with water dropinglets form sulfuric acid h2so4.
· sulfur dioxide is a precursor of sulfate particulates.
major carbon containing compounds:
carbon monoxide is a colorless, odorless, flammable gas
produced from incomplete combustion in petrol-engined motor cars &
cigarette smoke.
co effects:
it is highly poisonous to human and most
animals, co reduces the ability of hemoglobin to attack oxygen.
co2 is a key greenhouse gas.
volatile organic compounds:
organic gases are those that contain both
hydrogen and carbon but may also contain other atoms. hydrocarbons (hcs) are
organic gases that contain only hydrogen and carbon, e.g. methane ch4.
metals as pollutants: lead
is a highly toxic material.
particulate matters (aerosols) are solid or liquid particles
composed of one or several chemicals. e.g. dust, pesticides, pollen, bacteria
cells, sulfate, nitrate.
sources
industrial and agriculture activities, natural sources: dust
storm.
effects:
¨ diverse health effect.
¨ urban haze leading to visibility reduction.
water pollution
human
impact on water cycle:
1. polluting the water cycle.
2. withdrawing water resources.
consequences of overdrawing surface water:
¨ inevitable shortage.
¨ ecological effects.
consequences of overdrawing ground water:
¨ falling water tables and depletion.
¨ diminishing surface water.
¨ land subsidence.
¨ salt water intrusion.
chemical
pollutants of water:
organic chemicals: many of these compounds come from living things, while
others are made in laboratories.
synthetic organic substances include: gasoline, oils, plastics,
some pesticides and fertilizers, solvents, and wood.
crude oil is one of the most common and
dangerous organic pollutants. crude oil enters surface water systems as a
result of spills at drilling sites, or from shipwrecked or damaged oil tankers.
inorganic chemicals: include acids, salts, and heavy metals. examples of
dangerous heavy metals: mercury, lead, cadmium, nickel, and chromium. heavy
metal compounds are often by products of industrial processes such as metal
treatment, paints, and plastic production.
factories sometimes discharge these materials directly into
surface water. heavy metals are poisonous, ingestion of these materials can
cause brain, liver, and kidney damage.
radioactivity:
radioactive elements give off radiation
when they decay. radioactive elements such as uranium 235 and plutonium 239 are
used as:
¨ fuel in nuclear power plants.
¨ others are used in medicine.
¨ uranium mines and nuclear fuel.
¨ refineries produce radioactive waste.
the disposal of radioactive waste both
solid and liquid may result in water pollution.
plants
nutrients and cultural eutrophication:
plants in water require a sufficient
supply of nutrients to grown and mature properly. the most common nutrients
found in out water are: nitrogen, phosphorous and carbon. large amount of
nutrients can cause problems such as algae blooms.
algae is a general term of small,
chlorophyll containing plants such as seaweed. when a body of water has a high
level of nutrients, aquatic plants will grow and reproduce quickly. if algae
grow in high density it will block the sunlight from reaching plants at greater
depth lead to death. when algae die, the decaying process uses oxygen in water
decreasing o2 dissolved, this will cause aquatic animals to die. the
process of aquatic overgrowth of algae, followed by death, decay, and o2depletion is called eutrophication, this can result from human
influences on the chemicals that enter water. (this process causes an imbalance
between plants & animals in the water)
thermal
pollution of water:
power plants and other industrial
facilities give off large amount of heat, which can pollute water.
a large increase in water temperature due
to human activities is called thermal pollution. thermal pollution usually
occurs in lakes, rivers, or shallow bays located near power plants or
industrial sites.
an increase in water temperature
decreases the amount of dissolved oxygen the water can hold (bod).
the fish suffocate because they cannot get enough oxygen.
the increase in water temperature is also
destructive to developing eggs and young fish.