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by Dr PHUA Kai Lit
School of Medicine and Health Sciences
Monash University Sunway Campus
Bandar Sunway, Malaysia


Defined as the "study of the distribution & determinants (causes) of disease".

(1) Distribution by ethnicity ("race"), class (working, middle, upper class), gender ("sex"), age, region (rural, urban, suburban. Also, low income, middle income and high income country), educational level, occupation, marital status (single, married, widowed, divorced)

(2) Determinants e.g. tobacco smoking and lung cancer. Problem of multiple causation.


(1) Physical environment: Air, water and land around us e.g. desert and sand storms affecting the lungs, mountain and "thin air" problem, cities and air pollution

(2) Biological environment: Exposure to disease-causing organisms, vectors of disease such as flies and mosquitoes

(3) Socioeconomic environment e.g. crowded slum housing and TB, squatter areas sited next to smokestack factories


Diseases of the lungs and respiratory system

Respiratory tract infections e.g. URTI (Upper Respiratory Tract Infection)
Lobar and bronchopneumonia
Chronic bronchitis & emphysema
Tumours (cancers) e.g. lung cancer, nasopharyngeal cancer
Occupational lung diseases e.g. silicosis, asbestosis, byssinosis ("brown lung disease" of textile workers), "black lung disease" of coal miners
Legionnaire's disease (water from air-conditioners may contain the bacteria)


Indoor Air Pollution
(a) Home - tobacco smoke (passive smoking from environmental tobacco smoke or ETS), smoke from fires (cooking, heating e.g. fireplaces, lighting e.g. candles and oil lamps), chemicals (sprays, paints, carpets), radiation (radon gas), asbestos (insulating material, fire-retarding material)

(b) Temples - joss sticks, candles, oil lamps

(c) Workplace - chemicals (paints, solvents), dust (silica, metal or wood dust), asbestos fibres, harmful gases, radiation

Outdoor Air Pollution
(a) Motor vehicle exhaust - lead, sulphur dioxide etc

(b) Factory emissions

(c) Radiation

(d) Smoke from fires e.g. the "Haze"


Primary, secondary and tertiary prevention

Primary prevention - prevent the disease from actually occurring e.g. BCG vaccination against tuberculosis, make the workplace safer - reduce exposure to dust, chemicals, smoke, radiation (ventilation, respirators, lead shields against radiation)

Secondary prevention - early detection and prompt treatment e.g. X-rays of lungs to detect silicosis

Tertiary prevention - rehabilitation & restoration of as much of affected function as possible


Tobacco smoke contains over 2,000 dangerous chemicals

Smokers - lower class people, males (but more and more females are smoking)

People usually start smoking during teenage years. They become addicted to nicotine

Increases risk of cancers of the respiratory system. Also increases risk of heart disease, stroke, hypertension, low birthweight babies in pregnant women

Contradictory positions to tobacco in Malaysia e.g. anti-smoking campaigns. But, Govt also has a National Tobacco Board to promote tobacco cultivation among farmers. Govt also derives tax revenue from tobacco. Govt radio and TV derive revenue from advertising of tobacco. Govt bodies also invest in tobacco companies e.g. EPF is a shareholder in British American Tobacco Malaysia (BAT).


The 4E's Approach

ECONOMIC - high taxes on tobacco and tobacco products

ENFORCEMENT - illegal to sell cigarettes to people below a certain age, restrict advertising

EDUCATION - health education campaigns (focus on children and teenagers)

ENVIRONMENTAL MODIFICATION - prohibit cigarette vending machines, establish no smoking areas