Page 252 - Textbook of Pathology, 6th Edition

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Environmental and
Chapter 9
Chapter 9
Nutritional Diseases

SECTION I
INTRODUCTION Non-therapeutic toxic agents (e.g. alcohol, lead, carbon
monoxide, drug abuse)
Environmental chemicals
The subject of environmental hazards to health has assumed
great significance in the modern world. In olden times, the 3. Injury by physical agents:
discipline of ‘tropical medicine’ was of interest to the Thermal and electrical injury
physician, largely due to contamination of air, food and water Injury by ionising radiation
by infectious and parasitic organisms. Subsequently, the 4. Nutritional diseases:
interest got focussed on ‘geographic pathology’ due to Overnutrition (obesity)
occurrence of certain environment-related diseases confined Undernutrition (starvation, protein energy malnutrition,
to geographic boundaries. Then emerged the knowledge of vitamin deficiencies).
‘occupational diseases’ caused by overexposure to a pollutant
by virtue of an individual’s occupation. Currently, the field
of ‘environmental pathology’ encompasses all such diseases ENVIRONMENTAL POLLUTION
caused by progressive deterioration in the environment, most Any agent—chemical, physical or microbial, that alters the
of which is man-made. In addition, is the related problem of composition of environment is called pollutant. For survival
over- and undernutrition. of mankind, it is important to prevent depletion of ozone
Some of the important factors which have led to the layer (O ) in the outer space from pollutants such as
3
alarming environmental degradation are as under: chloroflurocarbons and nitrogen dioxide produced in
1. Population explosion abundance by day-to-day activities on our planet earth due
2. Urbanisation of rural and forest land to accommodate to industrial effluent and automobile exhausts.
the increasing numbers
General Pathology and Basic Techniques
3. Accumulation of wastes AIR POLLUTION
4. Unsatisfactory disposal of radioactive waste
5. Industrial effluents and automobile exhausts. A vast variety of pollutants are inhaled daily, some of which
But the above atmospheric pollutants appear relatively may cause trivial irritation to the upper respiratory path-
minor compared with voluntary intake of three pollutants—use ways, while others may lead to acute or chronic injury to the
of tobacco, consumption of alcohol and intoxicant drugs. The lungs, and some are implicated in causation of lung cancer.
WHO estimates that 80% cases of cardiovascular disease and Whereas some pollutants are prevalent in certain industries
type 2 diabetes mellitus, and 40% of all cancers are (such as coal dust, silica, asbestos), others are general
preventable through ‘three pillars of prevention’: avoidance pollutants present widespread in the ambient atmosphere
of tobacco, healthy diet and physical activity. The WHO has (e.g. sulphur dioxide, nitrogen dioxide, carbon monoxide).
further determined that about a quarter of global burden of The latter group of environmental pollutants is acted upon
diseases and 23% of all deaths are related to modifiable by sunlight to produce secondary pollutants such as ozone
environmental factors. Infant mortality related to and free radicals capable of oxidant cell injury to respiratory
environmental factors in developing countries is 12 times passages. In highly polluted cities where coal consumption
higher than in the developed countries. and automobile exhaust accumulate in the atmosphere, the
Attempts at prohibition of alcohol in some states in India air pollutants become visible as ‘smog’. It has been reported
have not been quite effective due to difficulty in implemen- that 6 out of 10 largest cities in India have such severe air
tation. Instead, prohibition has only resulted in off and on pollution problem that the annual level of suspended
catastrophe of ‘hooch tragedies’ in some parts of this country particles is about three times higher than the WHO standards.
due to illicit liquor consumption. An estimated 50,000 persons die prematurely every year due
The present discussion on environmental and nutritional to high level of pollution in these cities.
diseases is covered under the following groups: The adverse effects of air pollutants on lung depend upon
a few variables that include:
1. Environmental pollution: longer duration of exposure;
Air pollution total dose of exposure;
Tobacco smoking impaired ability of the host to clear inhaled particles; and
2. Chemical and drug injury: particle size of 1-5 μm capable of getting impacted in the
Therapeutic (iatrogenic) drug injury distal airways to produce tissue injury.