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Environment as a determining factor of health
Maria Rosa Girbau and Katy Salas
Lecturers at the Escola
Universitària d'Infermeria (University College of Nursing), University
of Barcelona
The state of the environment is a key factor
for the well-being of both individuals and society as a whole. Moreover,
many experts defend the idea that a suitable environment is a fundamental
human right and this has been acknowledged by the Catalan Parliament.
The writers of this article explain the hazards that are affecting the
environment and that consequently pose a threat to people's health.
Up until the first half of the twentieth century, man paid little attention
to the consequences of his impact on the environment and it was only
after the Second World War that people began to be aware of the implications
of man's actions on the environment and people's health.
Certain events, such as the nuclear bombs on Hiroshima and Nagasaki,
the oil crisis and the foreseeable depletion of other minerals, the
destruction of the ozone layer, proof of climatic change, the hazardousness
of many natural and synthetic products, unpredictable natural disasters,
the new strain of Creutzfeldt Jakob disease, etc., have all made it
very clear that indiscriminate action by man on the environment has
a boomerang effect that directly works against man himself. The words
of ecologist Ramon Margalef are poignantly fitting, "Maybe it is
us who are the planetary cancer, and it is our quality of life and survival
that are endangered and not that of planet Earth".
The environment has been considered a determining factor of people's
health for many years although it was not until the 1970s that different
models appeared to explain the causes of health impairment in inhabitants
in the developed world. Some of these models pointed to the holistic
component (Laframboise 1974) as being the cause of disease-related mortality
while others referred to the ecological model (Austin and Werner 1973),
and that of well-being (Travis 1977).
Regular advances were made concerning the genesis of contemporary diseases
on the basis of these initial contributions and in 1974 the Canadian
Minister of Health Marc Lalonde, who had worked on developing previous
models, presented a report on the health of the population in Canada
entitled "New perspectives on the health of the Canadian population".
The report described genetic factors, environmental factors, lifestyle
and the health system as being the main determinants. New concepts concerning
the determinants of health have appeared in recent years and can be
classified on five different levels: biological, physical and psychic
determinants; lifestyle determinants; environmental and community determinants;
physical environment, climate and environmental pollution determinants;
and, lastly, the factors determining macrosocial structure, politics
and a population's outlook on life.
The environment is thus clearly a fundamental element affecting the
wellbeing of both individuals and society as a whole, which calls for
a new kind of environmental awareness based on shared responsibility,
which in turn involves a change in people's attitudes based on the principle
of environmental solidarity.
In this respect, the Secretary General of the United Nations Organisation
(UNO), Kofi Annan, at the World Summit on Social Development in 1995,
contended that "a healthy society is one that takes care of its
members and gives them the opportunity to participate in the decisions
that affect their lives" and therefore their health.
At the same time, one should be aware that both social and economic
well-being are concepts that progress in tandem with sustainable development
although it is very clear that people are not sensitive to the question
of environmental problems until these are defined and socially accepted,
which shows the importance of the media in making people aware of the
hazards.
From an initial overall view of the human being, health is understood
to be a process of balance or harmony between the different dimensions
that make up the individual and his or her external environment. Man
is a key element in maintaining the necessary balance and it stands
out that the physical, biological and social environment plays a highly
important role in contemporary disease and illness (cardiovascular,
respiratory, and digestive problems, cancer, allergies, spongiform disease,
etc.), with new problems being generated in the realm of public health.
On the basis of these considerations, there is a need to involve the
different institutional, social, political, economic and professional
actors for it is these who ultimately are directly or indirectly responsible
for people's health.
Historical background
The oldest known
reference to the relationship between man and the environment dates
from the 5th century BC. The Treatise on Airs, Waters and Places by
Hippocrates (460-377 BC), states that, in order to understand health
and disease, man must be studied in his normal state and in relation
to the environment where he lives, together with the causes that have
disturbed the balance between man and his external and social environment.
Hippocrates' ideas were applied to construe the environmental conditions
of human life and they can thus be considered to be one of the earliest
roots of human ecology, along with Aristotle's works on natural history.
This ecological approach has unfortunately not prevailed in the field
of the health sciences that, for different reasons, have been highly
influenced by physiology and the study of man's internal environment
that began in France during the 19th century, and reinforced by the
advances made in the 20th century in the field of diagnosis and therapy.
At the same time, the role of the physical, psychic and social environment
in the genesis of health or disease in man has been overlooked.
In 1948, the United Nations General Assembly adopted and proclaimed
the Universal Declaration of Human Rights, in which the environment
itself is not dealt with explicitly although note can be made of several
of its articles in that they demonstrate institutional and governmental
responsibility with respect to the protection of the individual.
Article 1 states that "All human beings… should act
towards one another in a spirit of brotherhood". Here, the principle
of solidarity is laid down.
Article 3 states that "Everyone has the right to... security
of person", which therefore institutes the right to live with guarantees.
Article 6 states that "Everyone has the right to recognition
everywhere as a person before the law". This can be understood
to mean the right to be protected.
Article 21.1 states that "Everyone has the right to take
part in the decision-making process...", which assumes that people
must actively participate in decisions that may compromise their integrity.
From the second half of the 20th century onwards, the ecology movement,
together with an increased awareness of environmental issues, led to
the UNO taking initiatives and it was from this point on that a series
of far-reaching international conferences began to be held. The first
world summit, known as "Only One Earth", was held in Stockholm
in 1972, with the object of assessing the hazards resulting from pollution
of the human environment. The bases for achieving international agreement
on issues involving the environment were established here, and it also
led to the United Nations Environment Programme (UNEP) being established.
The differences and difficulties in reaching global agreements on the
problems affecting both rich and poor countries, which still persist
today, became evident at this international summit where Indira Gandhi
is attributed with saying, "environmental problems in the developing
countries are not the collateral effects of excessive industrialisation
but a reflection of the inadequacy of development".
At the 30th World Health Assembly in the city of Alma-Ata (1977), the
World Health Organisation (WHO) agreed to draw up a series of objectives
for achieving health for all by the year 2000, amongst which appeared
the preservation of the environment. In 1984, the European Regional
Office drew up a list of 38 objectives, corresponding to Europe, that
made explicit reference to the creation of healthy environments (objectives
nos. 18 to 25).
Various other global conferences were held during the 1990s, including
the International Conference on Health Promotion (Ottawa, 1986), the
Montreal Protocol (1987) on the protection of the ozone layer; the Sundswall
Conference (Sweden, 1991), and several preparatory ones preceding the
Earth Summit in Rio de Janeiro in 1992, with the sole objective of making
progress in the knowledge of environmental hazards.
The purpose of the Rio Summit (1992), or "Earth Summit" as
it is known, was to achieve a balance between social and economic needs
and environmental needs, and three fundamental documents were drawn
up:
- Agenda 21, considered
to be a declaration of principles based on a world plan of action
for promoting sustainable development.
- The document
on Climatic Change, with the objective of reducing the gases responsible
for the greenhouse effect.
- The document
on Biological Diversity, which exhorted countries to undertake measures
to conserve plant and animal species, with a series of directives
on the most sustainable ways of managing forests.
The "Earth Summit + 5" was held in New York in 1997, with
the purpose of determining and recognising the objectives achieved in
applying the agreements reached in Rio.
As far as Climatic Change is concerned, summits have been held in Kyoto
(Japan, 1997), The Hague (2000) and Bonn (2001), with somewhat disappointing
results.
Other interesting initiatives that have reinforced some of the proposals
presented at the different international forums include the reports
presented by the Club of Rome in 1972, including the one entitled "The
limits of growth", which was updated in 1992 with the title "Beyond
the limits of growth".
Also worthy of mention is the Brundtland Report (1987), which expounded
the idea of "meeting present needs without compromising the ability
of future generations to meet their own needs", and established
the relationship between sustainable development and economic systems.
An example of a local level project is the one by the Barcelona City
Hall known as Barcelona Agenda 21, in which the commitments to face
the new environmental challenges of the 21st century, together with
the social, urban and economic development of the city in a sustainable
way with the environment, are made manifest.
Risks associated
with unsustainable development
Man's egocentric
activities imply a potential risk to the health of both individuals
and society as a whole in that the environment in which we live is highly
dynamic due to the action of different cycles (carbon, nitrogen, water,
etc.). It is also highly complex because there is an exchange of energy
and matter and, at the same time, a constant interrelationship of elements
on the different gradients or levels in nature, and the effects of man
can break the fragile balance of the environment and endanger its integrity.
The possibility therefore of man being able to live in healthy conditions
depends on his ability to adapt to changing conditions, and this ability
is related to physical, biological and social factors.
In general terms, pollution can be defined as the alteration of the
properties of an environment due to the incorporation, generally as
a result of the direct or indirect action of man, of particles, gas
compounds, disturbances, materials or radiation that lead to modifications
in the structure and function of the ecosystems affected.
When asking the question of what the potential risks to health are,
certain factors need to be taken into account which are closely linked
to how serious the effect is, such as:
- the characteristics
and degree of solubility of pollutants
- the quantity
of substance or pathogen
- the period of
exposure to risk
- the mechanisms
of action or toxicodynamics
- the defence
mechanisms of the affected organ and/or tissue
- the entry route
and subsequent transformation of the substance
- immunity characteristics,
and other variables that make the individual more susceptible, such
as age, previous pathologies, etc.
Atmosphere
The atmosphere
is the layer of gas that forms a sphere surrounding the Earth. It is
made up of a mixture of gases in variable proportions according to altitude
(troposphere, stratosphere, mesosphere and thermosphere) and is responsible
for the temperature.
Atmospheric pollution is the degradation of the layer of gases due to
the increase of elements that are normally present or by the presence
of substances and/or particles that are foreign to its normal composition.
Air pollution is a process that begins with gas and/or particle emissions
and man has been exposed to it since the discovery of fire, although
unsustainable development has increased the quantity and quality of
polluting agents and today affects both industrialised and developing
countries.
The presence of pollutants in the atmosphere may be the result of natural
causes such as volcanic eruptions, soil erosion, sand storms, earthquakes,
anaerobic fermentation processes, plant pollination, etc. and/or anthropogenic
and/or artificial causes, such as road traffic, industrial processes
and power stations, domestic and industrial heating, waste incineration,
nuclear testing, war, etc.
Man ingests different harmful elements by way of the respiratory tract
(into the lungs by inhaling), by contact with the skin (cutaneously)
and orally (by direct or indirect ingestion).
Inhalation: Gases, vapour, aerosols and particles in suspension
can all penetrate the respiratory organs. Size and shape, together with
an individual's respiratory parameters determine the levels of pollutant
absorption and penetration to the deeper respiratory tracts.
Skin contact: Many substances can penetrate the skin, such as biocides
and organic solvents. Factors to be taken into account are the condition
of the skin (erosion of the skin makes absorption easier), body temperature
and peripheral circulation (an increase in these leads to higher absorption).
Oral ingestion: This is the most frequent way that pollutant
substances found in drinking water enter the body.
These substances are mainly metabolised by the liver, kidneys, lungs,
skin and the gastrointestinal tract, with elimination occurring mainly
via the urine and bile. The elimination of volatile and gaseous substances
is by way of exhaling.
There are numerous effects of air pollution and it is both difficult
to quantify them and to establish causal relationships. Mention should
be made, however, of the fact that they are especially dangerous for
people with chronic pulmonary illness (emphysema, bronchitis, asthma),
for the elderly and for babies. According to the WHO, between 30-40%
of the cases of asthma and 20-30% of all respiratory problems may be
related to air pollution in certain towns and cities, and it is considered
to be one of the main causes reducing life expectancy in general, together
with non-disabled life expectancy.
Some of the most significant aspects due to its effects on health are
as follows:
- Carbon monoxide
(CO): non-water soluble in the mucous membranes of the respiratory
apparatus, which facilitates its ability to penetrate the alveolar
walls, with a great affinity for one of the four iron atoms in the
haemoglobin molecule (210-240 times more than oxygen molecules), which
transforms it into carboxyhaemoglobin. This interferes with
the correct exchange of gases in the capillaries and produces anoxia
due to lack of O2.
Clinical manifestations include cephalalgia, dizziness, faintness,
nausea and vomiting. Serious intoxication can lead to cardiac irregularities
due to myocardial ischemia, which can cause angor and infarct; neurological
disturbances with obnubilation and coma; cutaneous irregularities,
with pallor and cyanosis; and psychomotor dysfunctions with co-ordination
impairment.
- Sulphur oxides
(SOx): water-soluble, which facilitates absorption in the upper
sections of the respiratory tract, causing irritation of the mucous
membranes and bronchial constriction. Clinical manifestations may
worsen if they interact synergically with other particles in suspension
in the atmosphere, which facilitates penetration to the alveola. They
also stimulate the taste and smell senses.
- Nitrogen
oxides (NOx): non-water soluble in the mucous membranes of the
respiratory apparatus, these penetrate the alveolar walls, where they
combine with haemoglobin (Hb) and are transformed into nitrosamines
with carcinogenic properties. Clinical manifestations include irritation
of the mucous membranes, pulmonary edema, chronic pulmonary fibrosis
and death due to asphyxia.
- Tropospheric
ozone (O3):
a secondary pollutant formed by the action of ultraviolet radiation
on the oxygen molecules, which transform by dissociation into two
reactive atoms that subsequently combine together with other oxygen
molecules to form an ozone molecule. It is insoluble, which facilitates
penetration in the respiratory tract. Clinical manifestations include
irritation of the mucous membranes, dry throat, cephalalgia, fatigue,
decline, an increased breathing rate, a decrease in the pulmonary
function, and it is even related to a decrease in the ability to concentrate.
- Solid particles:
the degree to which these have an effect is in relation to their ability
to penetrate the pulmonary cavities, which has to do with molecular
size and their affinity with the humidity of the air. They can act
as inert particle deposits on the alveolar walls, which hinders gaseous
exchange. They can also affect people through the ingestion of foodstuffs
made of ingredients affected by particles that have been absorbed
by plant life through dry deposition.
- Others:
such as fluorides, lead, mercury, cadmium and asbestos. As a result
of their ability to volatilise, they are absorbed by breathing and
can lead to irritation of the mucous membranes and respiratory difficulties.
Some, like asbestos, are potentially carcinogenic.
With respect to the effects on the atmosphere, mention must be
made of the influence of carbon dioxide (CO2), nitrogen oxides (NOx),
methane (CH4), chlorofluorocarbons (CFC) and ozone (O3) on the greenhouse
effect. This is the increase in temperature due to the presence
of gases in the layers of the atmosphere that prevent infrared (long
wavelength) radiation from escaping out into space, which contributes
to the warming of the atmosphere.
Its effects on health are linked to shifts in the increase of average
air temperature, with alterations to ecosystems and loss of biodiversity.
This therefore hinders the availability of food resources, the destruction
of natural habitats due to the increase in sea-level (which in turn
contributes to human migrations) and an increase in diseases transmitted
by vectors (malaria), due to the increase in humidity.
Predictions are constantly being made in order to assess the impact
according to the different potential scenarios (population, radiation,
humidity, precipitation, erosion, agriculture, forests, absorption mechanisms
in plants and oceans, etc.).
The presence of chlorofluorocarbons (CFCs) in the layers of the atmosphere
causes depletion of the ozone layer situated in the stratosphere and
formed of O3. The depletion of this layer is produced by the action
of CFCs, which are highly volatile and chemically stable gases used
in refrigeration units, pesticides, air conditioning, aerosols, foam,
etc. On reaching the stratosphere, they are broken down by the action
of ultraviolet rays and give off chlorine and bromide molecules that
destroy the ozone.
This layer is vital for living beings in that it protects them from
the sun's ultraviolet radiation. The decrease in stratospheric ozone
is connected with the appearance of melanomas, cataracts and inhibition
of the immune system.
Other harmful effects are due to acid rain, which leads to the
acidification of the components in ecosystems; temperature inversions,
which impede the vertical circulation of pollutants and their dispersion;
and photochemical smog, with clinical manifestations in the form
of coughs, nose and throat irritation, bronchial constriction, visual
impairment and inability to concentrate.
The vulnerability of plants to atmospheric pollution must also
be taken into account. They can suffer from growth retardation, yellowing
of the leaves and death in extreme situations. Animals as well are vulnerable
and they can undergo a decline in productivity, breeding irregularities
and death by poisoning on ingesting contaminated plant matter.
The most outstanding material effects are the social consequences
of the loss of architectural and artistic heritage, together with the
cost of restoration and maintenance of damaged structures.
Water
Water is essential
for life. All living beings are made predominantly of water and it is
the most abundant substance on the planet, two thirds of which is covered
with water. 97% is found in liquid form in the ocean, 2.25% is in a
solid state in the ice caps, glaciers and in the form of snow, a small
quantity occurs in the form of vapour in the atmosphere and a mere 0.75%
is fresh water apt for human consumption when it is not polluted, in
rivers, lakes and underground aquifers.
A human being can survive with between 2.5 to 5 litres of water per
day. However, the demand in industrial societies can reach 500 litres
per person per day, taking into account all types of use and is also
the most demanding in terms of quality. The growing demand increasingly
reduces the time taken between the disposal of water supplied and the
next time it is used. The problem is thus one of quality and quantity.
In historical terms, water has played a very important role in the health
of the world's societies. 80% of all illnesses in the world are directly
or indirectly related to water (due to floods; drought; the transmission
of epidemics such as cholera and other diarrhoea-causing illnesses;
as a habitat for insects that transmit diseases such as malaria, dengue,
Rift Valley fever, etc.).
On the other hand, the introduction of personal hygiene, public sanitation
and advances made in microbiology have made an enormous contribution
to improving the quality of life and health of the world's population.
Water is therefore a precious and scarce asset. So much so, in fact,
that the European Water Charter was proclaimed in Strasbourg
in 1968. Point 1 states that "there is no life without water and
it is a treasure indispensable to all human activity". It ends
with point 12 that states that "Water knows no frontiers: as a
common resource it demands international co-operation".
Sources of water
pollution
Polluted water
is hereby understood to mean water containing substances that are alien
to the natural composition of water and/or micro-organisms that may
represent a hazard to people. In this case, it cannot be used for drinking,
cooking, irrigating crops, or in the food industries.
- Pollution
of urban origin: this results from all of the activities in a
town or city used fundamentally for domestic, commercial, small industry,
public infrastructure and transport purposes. This type of waste water
may carry a biological and chemical load.
- Pollution
of industrial origin: given the wide variety of different industrial
processes, waste water originating here may contain a chemical load
(heavy metals, various types of compound, etc.), a physical load (increase
in temperature, radioactivity) and a microbiological load (bacteria,
viruses, fungi, etc.). In spite of environmental protection laws,
the disposal of industrial waste water continues to present a high
risk for rivers, lakes and the sea, and thus for human health.
- Pollution
of agricultural origin: the great increase in the use of chemical
fertilisers to make crops more profitable, together with all types
of biocides to prevent plagues and disease from affecting plants,
has led to a great increase in the pollution of run-off water and
groundwater.
- Pollution
of livestock origin: liquid manure that is generated on today's
intensive livestock farms is a real problem in terms of elimination
due to the high content of nitrogen and other compounds, together
with the microbiological load.
- Marine pollution:
considering that coastlines are often highly built up and industrialised
areas, the waste water from these areas is the main source of pollution
constantly affecting marine waters but not the only one. The maritime
transport of passengers and goods is the other source that all too
often has been the origin of important ecological disasters, such
as spills of oil and other hazardous substances into the sea due to
accidents, or the cleaning of tanks at high sea by oil tankers (which
quite naturally is prohibited).
Types of pollutants
Pollutants in water
can be biological, chemical and physical.
Biological pollutants: these are microbiological agents capable
of causing infectious diseases in man and animals. They can be classified
as:
- Bacteria:
such as, for example, Vibrio Cholerae that produces cholera, an infectious
disease that causes vomiting, fluid evacuations that are similar to
rice water, acidosis and muscular cramps; Salmonella typhi, which
causes typhoid fever that comes on with the sudden appearance of fever,
asthenia, exanthema in the thorax and abdomen, hepatosplenomegaly,
and diarrhoea, as well as unconsciousness, and other types of salmonellosis,
etc.
- Viruses:
such as, for example, the hepatitis A virus, an infectious disease
that spreads by orofecal transmission, with a period of incubation
of between 15 and 60 days and produces fever, symptoms of discomfort
and non-specific digestive disorders and jaundice. It is endemic to
the Mediterranean basin. Enteroviruses: these cause digestive irregularities.
Adenoviruses: these cause adenoidal and amygdaloid irregularities.
Reoviruses: these can cause intestinal and/or respiratory irregularities.
- Parasites:
such as, for example, various types of amoebiasis, that cause
a dysentery-type syndrome that can subsequently spread and affect
other organs like the liver, lungs, kidneys, brain, etc, with amoebic
abscesses being produced. Helminthiasis (due to intestinal worms)
can occur in different phases of its life cycle (egg, larva, adult,
etc.).
- Fungi:
these reproduce by way of spores and some may be pathogens for man
and animals. They live in humid conditions, such as, for example,
around the edges of public swimming pools or on the ground where there
are public showers (athlete's foot).
Chemical pollutants:
these are chemical elements or compounds found in water from different
sources that may be toxic for human beings, animals, and aquatic flora.
Contact is either by ingestion of contaminated water, through the skin
and/or mucous membranes, especially if these are impaired in any way
(wounds, cuts, erosion, etc.), and by inhaling vapours or aerosols.
The repercussions that a particular chemical substance can have on a
person's health will depend on: its chemical form, its concentration,
the form of contact, the transformations it may undergo, either due
to reaction with other substances or processes of accumulation in the
food chain, and the susceptibility of the individual or group.
The most common pollutants are:
Nitrates: the concentration in surface waters is usually below
5 mgr/litre. These concentrations can be much higher in groundwater.
Direct consumption or food preparations for babies (feeding bottles)
using water with high nitrate concentrations can cause methaemoglobinaemia
(cyanosis due to hypoxia).
Fluorides: These are salts used in a wide number of industrial
processes, in chemical synthesis, insecticides, pesticides and rodenticides.
While fluoride is considered to be essential in preventing dental decay,
in high concentrations it can lead to fluorosis, which is characterised
by loss of weight, brittle bones, anuria, aesthenia, general discomfort,
rigid joints, and discoloration of teeth in the formation stage.
Mercury, lead, cadmium, nickel and other metals: these are highly toxic
and in general they tend to accumulate. Minamata disease (from the bay
in Japan) is a serious and complex set of toxic symptoms, with nervous
and psychic disorders due to the ingestion of mercury in the sea and/or
water polluted by spillage from vinyl chloride industries. Saturnism
is acute or chronic lead (or lead salt) poisoning and can be extremely
serious. Cadmium can be found in water as a result of industrial spills
and plastic and metal piping.
Arsenic: Therapy using arsenic has been used for over 3000 years
although it is also a very well known poison (it is merely a question
of dosage) that is highly toxic, produces vomiting, diarrhoea, the breakdown
of fat in the liver, and weakness in the limbs and even paralysis.
Selenium: certain selenium salts, such as selenium sulphide,
are used as a topical antimycotic for treating ringworm, as a keratolitic
and in scalp disorders (seborrheic dermatitis and dandruff). In large
doses it is highly toxic.
Organo-chlorate compounds: these are compounds found in insecticides,
pesticides, the best known being DDT, aldrin and endosulphan. They are
liposoluble and tend to accumulate. DDT has been found in the layer
of body fat in penguins in the Antarctic.
Hydrocarbons: Numerous hydrocarbons, particularly benzopyrenes
(which are potentially carcinogenic), have been found in seawater; they
have a low solubility in fresh water although this can increase with
the presence of anionic detergents (surfactants). These produce foam
in the turbulent stretches of rivers and obstruct waste water treatment
processes and the natural purification of currents. It has been compulsory
for detergents to be biodegradable since 1960.
Physical pollution: the temperature of water varies according
to the season of the year although if it is used as a coolant (in thermal
power stations and nuclear power stations), the increase in temperature
leads to an increase in solubility and alters the biological processes
that take place in it (colonies of legionella can form in the open part
of cooling towers for they need a certain temperature).
Radioactivity can occur in water for natural reasons (radioactive elements
in the lithosphere) although it is normally found as a result of the
radioactive activities developed by man.
Waste water
treatment:
The large demographic
increase, industrialisation and the intensification of livestock breeding
and agriculture that occurred during the 20th century have, as a whole,
by far exceeded the natural purification capacity of the water cycle,
as a result of which water has to be treated artificially.
There are various processing techniques in waste water treatment plants,
and these are either physico-chemical and/or biological.
Physico-chemical processing: in schematic terms, this consists of the
initial filtering of coarse material, a second filtering of smaller
material, a flocculation process (with ferrous sulphate or aluminium
chloride), a sedimentation process and lastly a sand bed filtering process
and then disposal into a river or sea by way of an ocean outfall at
a distance of various kilometres from the coast.
In the case of waste water treatment plants, a preliminary chlorinating
process is carried out after filtering to reduce the microbiological
load. The sand bed may be replaced by an active carbon bed (that has
a high absorption capacity) in the last phase, together with an oxidation
process using added ozone, and a final chlorinating process that makes
it apt for distribution to the mains network.
Biological processing is based on imitating natural purification.
It basically consists of filtering, with the water being passed through
pools of active clay (that contain bacteria capable of breaking down
the organic material) and fat separators. It is then subjected to a
sedimentation process and finally a decanting process.
Waste
Considering that
the soil plays a key role in the exchange of material and energy and
acts as an active receptor of all of the components in the air and in
water, waste constitutes a reservoir of micro-organisms that are potentially
hazardous and capable of infecting the population in general.
Man is an important factor that alters the dynamics of the soil, with
waste being uncontrollably dumped on the environment as a consequence
of the consumer model that modern day society has mistakenly chosen
and considers to be the product of wellbeing.
There are many causes for the increase in waste that is turning the
planet into a gigantic landfill site. This phenomenon is both of great
concern and dangerous because eliminating, processing and recycling
waste may compromise people's quality of life and impede the sustainable
development that is so avidly sought after.
From this perspective, it is important to understand the main causes
for the increase in urban waste in order to try and modify consumer
attitudes, reduce the volume of waste at source, and encourage waste
reuse, recycling and exploitation.
These causes include:
- Hygiene and
health needs, which have led to a spectacular increase in the use
of packaging and wrapping to prevent the risk of contamination in
handling and incorrect storage.
- The change of
eating habits, with an increase in the consumption of fast and pre-cooked
food.
- Urban growth
due to migration from rural areas, together with the demand for services
and an increase in consumption.
- The consumer
society, with its "use and throw away" habits, and an increase
in the use of paper, glass, plastic, cans, PVC, etc.
At the present time, five million people die every year as a result
of diseases connected with waste and a thousand million people are lacking
any type of garbage collection service. This is particularly serious
in the developing countries and makes the world's population highly
vulnerable to different pathogenic micro-organisms through the food
chain or by direct contact.
Helminthiasis, salmonellosis, ancylostomiasis, anthrax, leptospirosis,
tetanus, opportunistic mycoses, and toxoplasmosis, are just some of
the diseases that human beings can contract this way.
Different types of waste (urban and municipal, industrial, radioactive
and clinical) are generated by human activities, and the risk that they
present depends on the characteristics of the waste and how it is processed.
From the public health point of view, however, care needs to be taken
with the ways that waste is eliminated in order to guarantee that it
is totally harmless during collection, transportation and final disposal.
Selective collection (of glass, paper, plastic, cans, tetra brik aseptic
cartons, organic waste, medicaments, batteries, fluorescent light bulbs,
oil, domestic appliances): this is the most plausible means of recovery
because it reduces the volume of municipal waste, the consumption of
energy, water and raw materials, gas emissions, the consumption of chemical
fertilisers, it reduces pressure on landfill sites and incineration,
it impedes the presence of vectors and reservoirs (rodents, fleas, arthropodae),
and provides social benefits by creating jobs in the recycling industry.
Different ways of eliminating waste are as follows:
- Controlled
landfills: this entails difficulties, such as finding new spaces
where they can be located at a reasonable cost, places that are geologically
adequate and also willingly accepted by the neighbourhood.
- Incineration:
this way of partially eliminating waste is not totally risk-free for
public health because potentially carcinogenic substances like dioxins
are emitted into the atmosphere. A large proportion of clinical waste
contains chlorine, an element that remains undestroyed and forms hydrochloric
acid which can pollute the atmosphere.
- Underground
confinement and tanks: radioactive waste in Spain, particularly
that produced by nuclear power stations, is managed by the firm ENRESA.
The risks involved with this elimination technique are difficult to
assess because little is known about the long-term effects (radioactive
particles have a very long half-life).
Noise as a source
of pollution
Sound is the sensation
that an animal perceives by way of its hearing as a result of a disturbance
in the pressure and density in the material environment that surrounds
it (gas, liquid and/or solid), caused by a vibration that spreads out
in the form of a sound wave.
Two characteristics of sound are particularly interesting here:
1. Intensity: the degree of loudness of the acoustic vibration
or pressure, together with the alteration that is produced in the
air. It is measured in terms of dB (decibel) units. The measurement
scale is logarithmic, as to an arithmetic one, which means that an
increase of 3dB is equivalent to doubling the intensity of the perceived
sound.
The maximum permitted level, according to legislation in Spain,
is 85dB over 8 working hours. Measures must be taken to reduce noise
above this level.
The threshold level for hearing in human beings (young people) is
above 0, and the pain threshold is 125dB.
2. Frequency: this is the number of vibrations or cycles produced
per second. This is what is known as pitch, which goes from very low
frequencies (low pitch) to high frequencies (high pitch). The vibrations
are measured in Hz (Hertz). The human ear (a young person) can hear
deep sounds from 20Hz (frequencies below these are known as infrasound),
at the lower end, and up to 20,000Hz (above these are the ultrasounds)
at the high end.
Sound is one of the main forms of communication between animals and
human beings but it turns into noise when we perceive it as being uncomfortable
or when it produces a sensation of anxiety or repulsion; it can even
cause pain. The unpleasant sensation that is perceived can produce a
subjective (individual or cultural) and/or objective (well-informed)
disturbance to a person's physiology and behaviour that is/are observable
and/or measurable.
From the point of view of public health, continual exposure to noise
both at and away from work has become so important that a Congress on
Noise as a Public Health Problem was held in Washington in 1974. Two
years prior to this in 1972, it was recognised as being a pollutant
of the first magnitude at the Environment Summit held by the United
Nations in Stockholm. The WHO has estimated that there are 120 million
people in the world who have disabling hearing difficulties.
Noise forms part of most activities in urban life and this holds true
for the past as well as the present. In ancient Rome, as well as in
medieval cities, regulations existed to control both carriage transit
and working activities that were a nuisance to the inhabitants.
With industrialisation, the sources of noise pollution have increased
in quantity and variety. The main ones are: the transportation of people
and goods in both developed countries and large cities in the developing
world (cars, motorcycles, buses, coaches, trucks, conventional and high
speed trains, and planes), industry (machinery in operation), the building
and public works sector, leisure and entertainment installations (bars,
discotheques, open air restaurants, etc.), noise in the home (domestic
appliances, radio, TV, hi-fi, air conditioning, lifts, etc.) and in
offices (printers, photocopiers, drinks machines, etc.).
The harmful
effects of noise:
Aside from being
a nuisance, noise is also a risk to health. The effects of noise
can be divided as follows:
a) Specific effects on the hearing organ, b) effects on the physiology
or functioning of the rest of the organism, c) effects on behaviour
and activity.
a)
- Continuous exposure
(8 working hours) to noise louder than 85-90 dB constitutes a high
risk of deafness at work that in general is bilateral and irreversible
in the frequency bands of this type of noise.
- Occasional exposure
to loud noise (95-100dB) of different frequencies similar to discotheque
music produces what is known as hearing fatigue. This causes a temporary
loss of hearing ability, with the recovery time being directly proportional
to the time of exposure.
- Exposure to
a sudden short noise (pistol shot, firecracker, hammer blow, a bomb
explosion or a gas bottle explosion, for example) can produce a hearing
trauma that causes total deafness if it is loud enough and if the
individual affected is close to the source. This is a result of the
mechanisms of perception of the vibration and transmission of the
nervous impulse being affected, and is more or less reversible.
b) Continuous exposure to noise is described as being able to cause
arterial hypertension or ischemic cardiopathy in the cardiovascular
system. In the respiratory organs, it can produce apnea when the noise
is sudden and tachypnea (an increase in the respiratory rate) when it
is continuous.
Symptoms affecting the digestive system include a reduction in saliva
secretion, vulnerability to gastric ulcers, a decrease in intestinal
peristalsis, sluggish digestion, and nausea including vomiting.
Increased secretions of cortisone and adrenaline can occur in the endocrine
system. This is of special importance to pregnant women as it can lead
to a decreased irrigation in the womb and placenta, with an increase
in the cardiac rate of the foetus. The possibility of an increase in
glycemia has also been described.
Sound can affect the central nervous system in the form of insomnia,
anxiety, irritability and a decrease in the ability to concentrate.
Eyesight problems have also been observed, with a decrease in the field
of vision, difficulties in distinguishing colours and a decrease in
night vision, which may represent a hazard when driving.
- Impairment of
balance due to dizziness.
- Increase in
muscular tension.
- Increase in
skin sensitivity.
c) As far as behaviour
and activity are concerned, it is a fact that a noisy environment impedes
interpersonal oral communication. People become more nervous and aggressive,
they show signs of fatigue and emotional lability.
Background noise makes concentration and learning difficult. The risk
of making errors increases at work, together with the likelihood of
a higher accident rate.
Emphasis must be placed on the individual and cultural variability that
exists in perceiving sound as noise and in the effects it has on health.
Preventive
measures:
Different types
of measure can be adopted:
- Technical:
insulation at source (machinery can be insulated inside cabins; shock
absorbers can be used to reduce vibration; screens can be used to
separate them, etc.). Protection for people (helmets, earphones or
earplugs). Buildings (both working premises and housing can be built
with insulation materials, and carpets, curtains, wall hangings, etc.
used to deaden sound as well as being decorative).
- Legislation:
the drawing up of national, regional and municipal regulations on
noise generated by different sources.
- Education
is perhaps the most effective way of avoiding unnecessary noise at
its source. The benefits of educating people to respect the environment
are there for all because the behaviour of society as a whole is the
sum of all individual behaviour.
We believe, however, that the best strategy would be to incorporate
new consumer values in society and to develop attitudes that are much
more respectful of the environment in order to be able to continue
to enjoy this precious treasure that we have been given in the future.
As Einstein used to say, "An intelligent man is one who solves
problems, a wise man is one who avoids them".
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