CeLL reProDuCTIoN 361epithelial cells of the skin and intestinal lining, and red
blood cells, among other cell types. The results are
serious infections, intestinal hemorrhages, anemia, and
wounds that do not heal.
small doses of ionizing radiation over a long period
of time apparently cause less damage than the same total
dosage given all at once. This may be due in part to the
body’s ability to repair damaged DNA. even so, ionizing
radiation is associated with miscarriages, eye cataracts,
and various cancers (Chapter 22).
on the other hand, medical X-rays and diagnostic
technologies such as magnetic resonance imaging (mrI)
and PeT scanning (section 2.2) are valuable uses of
ionizing radiation in health care. so is radiation therapy
used in treating some cancers. Despite these positives,
recent studies have raised concerns about the relatively
high level of ionizing radiation that patients are exposed
to during mrI procedures, among others.Food may be irradiated to kill pathogens
Just as living body cells can be damaged or killed by
radiation, so can harmful bacteria, fungi, and other
microorganisms. As a result, foods ranging from grains
and potatoes to fruits, spices, beef, pork, and other
meats may be irradiated. Irradiated food sold in the
united states carries an identifying logo (Figure 18.8).
Irradiated food is not
radioactive, and some people
are quite comfortable eating it
because there is no scientific
evidence that it presents a health
hazard. In addition, irradiation
limits spoilage, and proponents
argue that it may reduce the
incidence of food-borne illnesses.
on the other hand, opponents
worry that irradiation might
promote the development of
radiation-resistant microbes.
some also are concerned that
irradiation may chemically change
food in ways that could harm
consumers. For the time being,
there is no scientific evidence to
support that fear.What do a routine dental X-ray and an irradiated side
of beef have in common? Both are examples of ways we
use ionizing radiation. Like some other technologies, this
one can be a double-edged sword and can even fuel
serious controversy.Irradiation has varying effects on the body
Ionizing radiation includes various potentially harmful types
of electro magnetic energy—for instance, radio waves,
visible light, microwaves, cosmic rays from outer space,
and radioactive radon gas in rocks and soil. Forms that can
harm living cells, including radon and X-rays, have enough
energy to remove electrons from atoms and change them to
positively charged ions (section 2.4).
When ionizing radiation enters an organism, it may break
apart chromosomes, alter genes, or both. If the chromosomes
in an affected cell have been broken into fragments, the
spindle apparatus will not be able to harness and move the
fragments when the cell divides. The cell or its descendants
may then die. When ionizing radiation damage occurs in
germ cells, the resulting gametes can carry damaged DNA.
Therefore, an infant who inherits the DNA may have a genetic
defect. If only somatic cells are affected, only the person
exposed to the radiation will suffer damage.
When a person receives a sudden, large dose of ionizing
radiation, it typically destroys cells of the immune system,18.5 Concerns and Controversies over Irradiation
SCIENCE COMES TO LIFE
Figure 18.8 Ionizing radiation can break apart chromosomes. The sources of radiation exposure for people in the United States.
Far right: Logo required to be placed on irradiated food products in the United States. (© John W. Gofman and Arthur R. Tamplin. From Poisoned Power:
The Case Against Nuclear Power Plants Before and After Three Mile Island, Rodale Press, 1979)Radon
54%Cosmic
8%Other chemical
sources (nonradon)
8%Chemical reactions
in the body
11%Medical X-rays
11%Nuclear
medicine
4%Appliances, other
consumer products
3%Other
1%Source: FDA.govCopyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).