Page 230 - Concise Pathology for Exam Preparation ( PDFDrive )

9 Environmental and Nutritional Pathology 215

c) Increased release of CO 2 and methane from organic matter in thawing ice (such as
arctic)
d) Decreased removal of CO 2 by diatoms due to their reduced growth; increased CO 2
increases the acidity of oceans which in turn disrupts the marine ecosystem
e) Increased heat energy in oceans induces variability in the weather events casing
floods, droughts and storms
• Climate change brings about cardiovascular, cerebrovascular and respiratory dis-
eases (owing to increased temperature and air pollution); increased incidence of
food- and water-borne diseases (contamination due to floods and disruption of clean
water supply); increased incidence of vector-borne infections (due to increased tem-
perature) and malnutrition (weather changes harm the crop production).

Q. Write briefly about the biological effects and mechanism of
action of ionizing radiation.
Ans. Radiation describes a process in which high-energy particles or waves travel through
a medium or space. There are two distinct types of radiation:
• Ionizing radiation: The word radiation is commonly used in reference to ionizing
radiation only (ie, having sufficient energy to ionize an atom). This occurs when an
electron is stripped (or ‘knocked out’) from an electron shell, and leaves the atom with
a net positive charge, eg, alpha particles (consist of two neutrons and two protons),
beta particles (consist of energized electrons), gamma rays (consist of photons with a
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frequency of greater than 10 Hz) and X-rays (electromagnetic waves with a wavelength
smaller than about 10 nm).
• Nonionizing radiation: Energy radiating (ie, travelling outward in straight lines in all
directions) from its source. The energy of nonionizing radiation is less and instead of
producing charged ions when passing through matter, there is only sufficient energy to
change the rotational, vibrational or electronic valence configurations of molecules and
atoms, eg, UV rays, infrared waves, microwaves and sound waves.
Radiation Units

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1. Curie (Ci): The amount of radiation emitted by a source (one Ci 5 3.7 3 10 disin-
tegrations per second of a radionuclide/radioisotope).
2. Gray (Gy): The energy absorbed by the target tissue per unit mass; corresponds to the
absorption of 10 erg/gm of tissue and is equivalent to exposure of tissues to 100 RAD
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(radiation absorbed dose). The unit ‘cGy’ (centigray) terminology has replaced ‘R’ (rads).
3. Sievert (Sv): Has replaced a term called ‘rem’. Sv quantifies a unit of equivalent dose
that depends on the biological rather than the physical effects of radiation (measures
the relative biological effectiveness of the radiation).

Morphological Effects of Radiation
• Deletions, breaks, translocations and fragmentation of chromosomes
• Disorderly mitotic spindles, polyploidy and aneuploidy
• Nuclear swelling/condensation/clumping of chromatin
• Breakdown of nuclear membrane
• Apoptosis
• Giant cells, pleomorphic nuclei, cytoplasmic swelling, degeneration of mitochondria
and endoplasmic reticulum and defects in plasma membrane
• Vascular changes, eg, endothelial swelling and proliferation with hyalinization of vessel wall
Hazards of Radiation

These are caused by the whole body irradiation having short wavelength and high fre-
quency. It may be electromagnetic waves like X-rays or particulate materials like a particles,
b particles, electrons, protons, neutrons, mesons and deuterons. The clinical manifestations
depend on the dose and duration of exposure to such radiation (Table 9.2).

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