Relation between environment and health

Prof. Madi Al Jaghbeer

• Content :

Definition of health and environment. Theories of disease causation. Environmental diseases. Environmental health. Environmental health actions (interventions).

• Health : according to WHO is a state of complete physical , mental and social well-being and not merely the absence of disease or infirmity .

• Environment : everything that surrounds us that is affected by us and is affecting us .

• Theories of diseases causation :

Humoral theory (Hippocrates).

Contagion theory (Fracastoro).

Germ theory ( Pasteur , Lister and Koch).

Current disease concepts .

• Humoral theory (Hippocrates) 430-330 B.C.

The Human body contains blood, phlegm , yellow bile and black bile . These are the things that make up its constitution and causes its pains and its health .

Health is primarily a state in which these constituent substances are in the correct proportion to each other both in strength and quantity and are well mixed .

Diseases arise from humoral imbalances and imbalances arise from natural causes :

1) Heredity : phlegmatic parents have phlegmatic children .

2) Regimen : Diet and other behavior .3) Climate : Temperature , wind and moisture .

Treatment either addresses :1) The causes of humoral imbalance : change in diet

or environment.2) Humoral imbalance itself : rid body of excess bile

or phlegm (induce vomiting , evacuation of bowels and veins were opened to let blood ).

• Contagion theory (Fracastoro) 1546

Contagion is a corruption which develops in the substance of a combination , passes from one thing to another and is originally caused by infection of the imperceptible particles .

He called the particles Seminaria (seeds). Differences between diseases are explained by

they’re having different “active particles” different seeds.

He did not abandon the humoral theory he blended it with his contagion theory suggesting that seeds for different diseases have different affinities for different humors .

Treatment : destroy or expel the seeds of contagion1) Destroy : extreme heat and cold.2) Expel : bowel movements , urination , sweating

and blood-letting .

• Germ Theory :

Pasteur (1850s) : Was able to show that yeast increased in weight , nitrogen and carbon content during fermentation , inferring that yeast is a living organism that is a cause of fermentation in beer and wine .

He challenged the theory of spontaneous generation : fermentation does not take place in absence of contamination by air.

Joseph Lister (1867): appreciated the significance of Pasteur’s theory , and stated “ it is not to its oxygen or to any of its gaseous constituents that the air owes this property but to minute particles suspended in it which are the germs of various low forms of life “ .

Robert Koch (1870-1880) : there are many different kinds of bacteria and specific kinds are responsible for specific disease .

• Current disease concepts :

1890 : researchers has recognized that microbes much smaller than bacteria are responsible for rabies and many other diseases , modern concept of virus originated.

1930s : antibiotic cures for bacterial infections .

Researchers in 20th century have revealed other causes of disease (other than infectious) :

1) Genetic 2) nutritional 3) immunological 4) metabolic 5) cytological .

Modern medicine classifies diseases according to:1) Organ systems : cardiovascular , renal , respiratory

etc…2) Pathogenesis : oncology , infectious , metabolic ,

nutritional etc…

• Environmental diseases

Lesions and diseases caused by exposure to chemical or physical agents in the ambient , workplace , and personal environment .

Personal environment : environment that pertains more to the individual and is greatly influenced by use of tobacco , alcohol ingestion , therapeutic and non-therapeutic drug consumption and the likes.

Factors in the personal environment generally have a larger effect on human health than does the ambient environment .

Environmental diseases could be encountered due to :

1) Disasters (Chernobyl nuclear accident ).2) Chronic exposure to relatively low levels of

contaminants .

Sensitivity of individual towards contaminants is affected by various factors :

1) Age .2)Genetic predisposition.3) different tissue sensitivities of exposed persons.

• Important environmental diseases :

Lung diseases : 1) Asthma : plant pollen , dust , mold and animal

dander.2) Black lung disease : coal miners’ lungs become

coated with coal dust causes chronic condition in which breathing becomes painful and difficult.

3) Bronchitis : Fire-fighters and smokers are at increased risk .

4) Asbestosis : breathing asbestos causes severe lung disorder could lead to lung cancer , asbestos was used for insulation in houses , schools and work-places before laws were passed to ban its use .

5) Silicosis : Lung disease caused by exposure to the silica in the dust of clay . Pottery workers are at increased risk .

Cancers :

beside lung cancer , environmental toxins that could lead to cancers : pesticides , herbicides , radioactive substances.

Liver or bladder cancer : in people working in plastic manufacturing.

Lung cancer : asbestos , chromium and coal tar.

Gulf war syndrome :

many US veterans have complained about symptoms that they attribute to their participation in the Persian – Gulf war in 1991.

Symptoms : chronic fatigue , aching muscles and joints , skin rashes , memory loss , miscarriages and babies born with birth defects.

Scientists do not know main cause but argue that veterans might be reacting to chemical weapons , biological weapons , pesticides , vaccines , oil fires or infectious diseases that they were exposed to .

Sick building syndrome

People attribute a variety of symptoms to the building were they work .

Common complaints : headaches , dizziness , nausea , tiredness , concentration problems , sensitivity to odors , dry itchy skin , dry cough , irritated eyes , nose and throat .

generally as soon as affected people leave the building their symptoms vanish and they feel well again .

Factors that may contribute : (1) Humidity(2) poor ventilation (3) poor temperature control(4) pollution from outdoor sources (pollen , car exhaust or

smoke )(5) chemicals from inside the building ( cleaning agents ,

glues , copy machine chemicals )(6) Bacteria ,viruses and molds .

Birth defects : infertility , miscarriages , still birth , childhood cancer and birth defects may have links to environmental toxins (pregnant woman exposed to lead her child has high risk of being born with behavior and nervous system problems).

Chemical poisoning : lead , mercury and cadmium.

• Environmental health

According to World Health Organization is the control of all factors in the environment which exercise a harmful effect on man’s physical development , health and survival .

The WHO’s definition is not all-inclusive in terms of the natural environment , and includes only those aspects that are modifiable (not necessarily immediately but with solutions that are already available ) .

• Examples of included environmental factors:

• 1) pollution of air , water , or soil with chemical or biological agents • 2) UV and ionizing radiation ( although natural UV radiation from space is not

modifiable or only in a limited way such as by reducing substances that destroy the ozone layer ) , individual behavior to protect oneself against UV radiation is modifiable .

• 3) noise , electromagnetic field .• 4) occupational risks.• 5) built environments including housing , land use patterns and roads.• 6) agricultural methods , irrigation schemes. • 7) man-made climate change , ecosystem change.• 8) behavior related to the availability of safe water and sanitation facilities such

as washing hands and contaminating food with unsafe water or unclean hands

• Examples of excluded environmental factors:• 1) alcohol and tobacco consumption and drug abuse.• 2) diet (although it could be argued that food availability influences

diet ).• 3) the natural environments of vectors that cannot reasonably

modified (e.g. in rivers , in lakes , in wetlands) .• 4) unemployment (provided that it is not related to environmental

degradation , occupational disease, etc). • 5) natural biologic agents such as pollen in the outdoor environment.• 6) person –to-person transmission that cannot reasonably be

prevented through environmental interventions such as improving housing , introducing sanitary hygiene or making improvements in the occupational environment.

• Environmental health actions (interventions)

First action (Sir Edwin Chadwick ) .

Current actions (WHO) .

• First environmental health action

Environmental health has its origins in the early 1800’s. The first public health act was introduced in 1842 as the result of a report made to parliament by Sir Edwin Chadwick on the sanitary conditions of the laboring population of Great Britain . The report told the story of disease caused , aggravated and spread by damp and atmospheric impurities produced by decomposing waste and overcrowding

In his report Sir Chadwick stated that “ the annual loss from filth and bad ventilation are greater than the loss from death or wounds in any wars in which the country has been engaged in modern times “ . He also stated “ the younger population bred up under noxious physical agencies is inferior in physical organization and general health to a population preserved from the presence of such agencies “.

Current environmental health actions

Environmental burden of disease (EBD).Country profiles of EBD .Health impact assessment .

• Environmental Burden of disease :

quantifies the amount of disease caused by environmental risks .

through : death incidence or DALY .DALY (disability adjusted life years ) : time based

measure that combines years of life lost due to premature mortality and years of life lost due to time lived in states of less than full health .

WHO report (2006 ) states that approximately one quarter of the global disease burden and more than one third of the burden among children is due to modifiable environmental factors.

Environmentally – mediated disease burden is much higher in the developing countries (communicable diseases) although in cases of certain non-communicable diseases ( CVD and cancers ) it is larger in developed countries.

Children bear the highest death toll with more than 4 million environmentally caused death per year especially in developing countries.

Diseases with high EBD :1) Diarrhea : 94% of the diarrheal burden of

disease is attributable to environment and is associated with risk factors such as unsafe-drinking water and poor sanitation and hygiene

2) Lower respiratory tract infections : 20% in developed countries and 42% in developing.

3) Other unintentional injuries : from workplace hazards , radiation and industrial accidents 44%

4) Malaria : 42% .

Total number of lives lost each year as result of environmental factors was 15 times higher in developing countries than developed countries.

Means of reducing EBD :1) Promotion of safe household water storage.2) better hygiene measures.3) use of safer and cleaner fuels.4) more judicious use and management of toxic

substances in home and work place .5) poverty reduction , well-being and economic

development.6) Cooperation between health sectors and other sectors

such as energy , transport , agriculture and industry .

• Country profile of environmental burden of disease :

Updated country data on the burden of disease that is preventable through healthier environments.

it provides an overview of summary information on selected parameters that describe the environmental health situation of a country as well as preliminary estimates of health impacts caused by environmental risks .

These country estimates are a milestone in a first step to assist national decision makers in the sectors of health and environment to set priorities for preventive actions .

1st step : quantifying the burden.2nd step : for countries to select appropriate

interventions .

• Health impact assessment (HIA) :

According to WHO is a combination of procedures , methods and tools by which policy or project may be judged as to its potential effects on health of the population and the distribution of those effects within the population .

Value of HIA :1) Better informed decision-makers and decisions.2) healthier land uses and community designs .3) increased awareness and understanding of

health consequences . Challenges of HIA :1) Lack of time2) Lack of resources (human and money ) .

Thank you very much

• References

1)World health organization ; environmental health topics .

2)The concept of disease :structure and change ; Paul Thagard ; University of Waterloo-Ontario ; Philosophy department ; (1997)

3) Robbins basic pathology ; Kumar , Abbas, Fausto and Mitchell ; 8th edition ; chapter 8 ; (2007)

4) Environmental diseases ; U.S. National Center for Environmental Health (NCEH), Centers for Disease Control and Prevention (CDC)

5) WHO ; Quantification of the disease burden attributable to environmental risk factors ; (2006).

6) Chadwick’s report on Sanitary conditions ; Laura Del Col ; West Virginia University; (2002)

7) Health impact Assessment : Quick guide ; National Association of County and city health officials ; (2008) .