Pathophysiology of environmental diseases

1. ENVIRONMENTAL
DISEASES
RVS CHAITANYA
KOPPALA

2. ENVIRONMENTAL DISEASES
Some of the important factors which have led to the alarming
environmental degradation are as under:
Population explosion
Urbanization of rural and forest land to accommodate the
increasing numbers
Accumulation of wastes
Unsatisfactory disposal of radioactive waste
Industrial effluents and automobile exhausts.

3. Atmospheric pollutants appear relatively minor compared with
vo luntary intake o f thre e po llutants— use of tobacco, consumption
of alcohol and intoxicant drugs.
The WHO estimates that 80% cases of cardiovascular disease
and type 2 diabetes mellitus, and 40% of all cancers are
preventable through ‘three pillars of prevention’:
Avoidance of tobacco,
Healthy diet and
Physical activity.
The WHO has further determined that about a quarter of global
burden of diseases and 23% of all deaths are related to modifiable
environmental factors.
Infant mortality related to environmental factors in developing
countries is 12 times higher than in the developed countries.

4. 1. Environmental
pollution:
Air pollution
Tobacco smoking
2. Chemicalanddrug
injury:
Therapeutic (iatrogenic) drug
injury
Non-therapeutic toxic agents
(alcohol, lead, carbon monoxide,
drug abuse)
Environmental chemicals
3. Injurybyphysical
agents:
Thermal and electrical injury
Injury by ionising radiation
4. Nutritionaldiseases:
Overnutrition (obesity)
Undernutrition (starvation, protein
energy malnutrition, vitamin
deficiencies).

5. Any agent—chemical, physical or microbial, that alters the
composition of environment is called pollutant.
For survival of mankind, it is important to prevent depletion of
ozone layer (O3) in the outer space from pollutants.
Pneumoconiosis—the group of lung diseases due to occupational
over-exposure to pollutants
ENVIRONMENTAL POLLUTION

6. AIR POLLUTION
which may cause irritation to the upper respiratory pathways, while
others may lead to acute or chronic injury to the lungs, and some are
implicated in causation of lung cancer.
Whereas some pollutants are coal dust, silica, asbestos, sulphur
dioxide, nitrogen dioxide, carbon monoxide.
The latter group of environmental pollutants is acted upon by
sunlight to produce secondary pollutants such as ozone and free
radicals capable of oxidant cell injury to respiratory passages.
In highly polluted cities where coal consumption and automobile
exhaust accumulate in the atmosphere, the air pollutants become
visible as ‘smog’.
An estimated 50,000 persons die prematurely every year due to
high level of pollution in these cities.

7. The adverse effects of air pollutants on lung depend
upon
A few variables that include:
Longer duration of exposure;
Total dose of exposure;
Impaired ability of the host to clear inhaled particles;
and
Particle size of 1-5 µm capable of getting impacted in

8. TOBACCO SMOKING
Habits
Tobacco smoking is the most prevalent and
preventable cause of disease and death.
The harmful effects of smoking pipe and cigar are
somewhat less.
Long-term smokers of filter tipped cigarettes appear to
have 30-50% lower risk of development of cancer due to
reduced inhalation of tobacco smoke constituents.

9. Smoking bidis and che wing pan m asala, z arda and
g utka are more widely practiced than cigarettes.
Habit of smoking chutta (a kind o f indig e no us cig ar) in
which the lig hte d e nd is put in mouth with higher
incidence of squamous cell carcinoma of hard palate.
Chewing of tabacco alone or mixed with slaked lime as
a bolus of paan ke pt in m o uth fo r lo ng ho urs which is the
major cause of cancer of upper aerodigestive tract and
oral cavity.
Hookah smoking, in which to bacco sm o ke passe s
through a water-filled chamber which cools the smoke
before it is inhaled by the smoker.

10. Besides the harmful effects of smoking on active smokers
themselves, involuntary exposure of smoke to bystanders
(passive smoking) is also injurious to health, particularly to infants
and children.

11. DOSE AND DURATION
It is estimated that a person who smokes 2 packs of cigarettes
daily at the age of 30 years reduces his life by 8 years than a
non-smoker.
On cessation of smoking, the higher mortality slowly declines
and the beneficial effect reaches the level of non-smokers after
20 or more of smoke-free years.

12. TOBACCO-RELATED DISEASES
Tobacco contains numerous toxic chemicals having adverse
effects varying from minor throat irritation to carcinogenesis.
The major diseases accounting for higher mortality in tobacco
smokers include the following (in descending order of frequency):
Coronary heart disease
Cancerof the lung
Chronic obstructive pulmonary disease (COPD).
Besides above, smokers suffer higher risk of development of a few
other cancers and non-neoplastic conditions.

14. THERAPEUTIC (IATROGENIC)
DRUG INJURY
 In general, the risk of adverse drug reaction increases with
increasing number of drugs administered.
Adverse effects of drugs may appear due to:
Overdose;
Genetic predisposition;
Exaggerated pharmacologic response;
Interaction with other drugs
Unknown factors

16. NON-THERAPEUTIC TOXIC
AGENTS
(ALCOHOLISM)Chronic alcoholism is defined as the regular imbibing of an amount
of ethyl alcohol (ethanol) that is sufficient to harm an individual
socially, psychologically or physically.
Adverse effects—acute as well as chronic, are related to the
quantity of alcohol content imbibed and duration of consumption.
Generally,
10 gm of ethanol is present in: Can of beer (or half a bottle of beer);
120 ml of wine 30 ml of 43% liquor (small peg).
A daily consumption of 40 gm of ethanol (4 small pegs or 2 large
pegs) is likely to be harmful
But intake of 100 gm or more daily is certainly dangerous.

17. ACUTE ALCOHOLISM
1. Nervous system:
Initial effect of alcohol is on subcortical structures which is
followed by disordered cortical function, motor ataxia and
behavioural changes.
These changes are apparent when blood alcohol levels do
not exceed 1 0 0 m g /dl which is the upper limit of sobriety in
drinking
Blood levels of 1 0 0 -20 0 m g /dl are associated with depression
of cortical centres, lack of coordination, impaired judgement
and drowsiness.

18. Stupor and coma supervene when blood alcohol levels are
Abo ut 30 0 m g /dl.
Blood levels of alcohol abo ve 40 0 m g /dl can cause
anaesthesia, depression of medullary centre and death from
respiratory arrest.
2. Stomach. Acute alcohol intoxication may cause vomiting,
acute gastritis and peptic ulceration.
3. Liver. Acute alcoholic injury to the liver

19. CHRONIC ALCOHOLISM
1. Liver. Alcoholic liver disease and cirrhosis are the most common
and important effects of chronic alcoholism.
2. Pancreas. Chronic calcifying pancreatitis and acute pancreatitis are
serious complications of chronic alcoholism.
3. Gastrointestinal tract. Gastritis, peptic ulcer and oesophageal
varices associated with fatal massive bleeding may occur.
4. Central nervous system. Peripheral neuropathies, cerebral atrophy,
cerebellar degeneration and amblyopia (impaired vision) are seen in
chronic alcoholics.
5. Cardiovascular system. Alcoholic cardiomyopathy and
myocardiosis with consequent dilated cardiomyopathy may occur.
Level of HDL (atherosclerosis-protective lipoprotein), however, has
been shown to increase with moderate consumption of alcohol.

20. 6. Endocrine system. In men, testicular atrophy, feminisation,
loss of libido and potency, and gynaecomastia may develop.
7. Blood. Haematopoietic dysfunction with secondary
megaloblastic anaemia and increased red blood cell volume
may occur.
8. Immune system. Alcoholics are more susceptible to various
infections.
9. Cancer. There is higher incidence of cancers of upper
aerodigestive tract in chronic alcoholics but the mechanism is
not clear.

22. DRUG ABUSE
Drug abuse is defined as the use of certain drugs for the
purpose of ‘mood alteration’ or ‘euphoria’ or ‘kick’ but
subsequently leading to habit-forming, dependence and
eventually addiction.
Some of the commonly abused drugs and substances are as
under:
1. Marijuana or ‘pot’ is psycho active substance m o st
wide ly used. It is obtained from the leaves of the plant
Cannabis sativa and contains tetrahydrocannabinol (THC). It
may be smoked or ingested.

23. 3. CNSdepressants include barbiturate s, tranq uilise rs and
alcohol.
4. CNSstimulants e . g . co caine and am phe tam ine s.
5. Psychedelic drugs (m e aning e njo yable pe rce ptio n-
g iving ) e.g. LSD.
6. lnhalants e . g . g lue , paint thinne r, nail po lish re m o ve r,
aerosols, amyl nitrite.

24. ENVIRONMENTAL CHEMICALS
A large number of chemicals are found as contaminants in the
ecosystem, food and water supply and find their way into the food
chain of man.
These substances exert their toxic effects depending upon their
mode of absorption, distribution, metabolism and excretion.
Some of the substances are directly toxic while others cause ill-
effects via their metabolites.
Environmental chemicals may have slow damaging effect or there
may be sudden accidental exposure such as the Bhopal gas
tragedy in India due to accidental leakage of methyl isocyanate
(MIC) gas in December 1984.

25. 1. Agriculture chemicals.
Modern agriculture thrives on pesticides, fungicides,
herbicides and organic fertilisers which may pose a potential
acute poisoning as well as long term hazard.
The problem is particularly alarming in developing countries
like India, China and Mexico where farmers and their families
are unknowingly exposed to these hazardous chemicals during
aerial spraying of crops.

26. 2. Volatile organic solvents.
Volatile organic solvents and vapours are used in industry
quite commonly and their exposure may cause acute toxicity or
chronic hazard, often by inhalation than by ingestion.
Such substances include methanol, chloroform, petrol,
kerosene, benzene, ethylene glycol, toluene etc.
3. Metals.
Pollution by occupational exposure to toxic metals such as
mercury, arsenic, cadmium, iron, nickel and aluminium are
important hazardous environmental chemicals.

27. 4. Aromatic hydrocarbons. The halogenated aromatic
hydrocarbons containing polychlorinated biphenyl which are
contaminant in several preservatives, herbicides and
antibacterial agents are a chronic health hazard.
5. Cyanide. Cyanide in the environment is released by
combustion of plastic, silk and is also present in cassava and
the seeds of apricots and wild cherries.
6. Environmental dusts. These substances causing
pneumoconioses while some are implicated in cancer

28. INJURY BY PHYSICAL
AGENTS

29. THERMAL AND ELECTRICAL
INJURY
Thermal and electrical burns, fall in body temperature below 35°C
(hypothermia) and elevation of body temperature above 41°C
(hyperthermia), are all associated with tissue injury.
Hypothermia may cause focal injury as in frostbite, or systemic
injury and death as occurs on immersion in cold water for varying
time.
Hyperthermia likewise, may be localised as in cutaneous burns,
and systemic as occurs in fevers.
Thermal burns depending upon severity are categorized into full
thickness (third degree) and partial thickness (first and second
degree). The most serious complications of burns are
haemoconcentration, infections and contractures on healing.
Electrical burns may cause damage firstly, by e le ctrical
dysfunction of the conduction system of the heart and death by
ventricular fibrillation, and se co ndly by he at pro duce d by electrical

30. INJURY BY RADIATION
As discussed in the preceding chapter, the most important form of
radiation injury is ionising radiation which has three types of effects
on cells:
Somatic effects which cause acute cell killing.
Genetic damage by mutations and therefore, passes genetic
defects in the next progeny of cells.
Malignant transformation of cells.
Ionising radiation is widely employed for diagnostic purpose as well
as for radiotherapy of malignant tumours.
Radiation-induced cell death is mediated by radiolysis of water in
the cell with generation of toxic hydroxyl radicals

31. During radiotherapy, normal cells ,endothelial cells of small arteries
and arterioles are effected causing necrosis and ischaemia.
Ionising radiation causes damage to the following major organs:
Skin: radiatio n de rm atitis, cance r.
Lungs: inte rstitialpulm o nary fibro sis.
Heart: m yo cardialfibro sis, co nstrictive pe ricarditis.
Kidney: radiatio n ne phritis.
Gastrointestinal tract: stricture s o f sm allbo we land oesophagus.
Gonads: te sticular atro phy in m ale s and de structio n o f ovaries.
Haematopoietic tissue: pancyto pe nia due to bo ne m arro w
depression.
Eyes: cataract.
Besides ionising radiation, other form of harmful

32. Besides ionising radiation, other form of harmful radiation is so lar
(u. v. )
Radiatio n which m ay cause acute skin injury as sunburns, chronic
conditions such as solar keratosis and early onset of cataracts in
the eyes.
It may, however, be mentioned in passing here that
electromagnetic radiation produced by microwaves (ovens,
radars, diathermy) or ultrasound waves used for diagnostic
purposes do not produce ionisation and thus are not known to
cause any tissue injury.

33. THANQ