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Chromosomes. being well-defined structures that are easily vis ible
under the optical microscope. readily lend themselves to in tense
physical and biochemical study. The understanding of the structure
and function of this most critical genetic material has progressed
through a number of interesting stages. Often connected with the
development of new techniques in staining and photography. using
the standard microscope and the electron microscope. It is
interesting to look back at the history of cytogenetics. I would
like especially to emphasize the work of Karl Sax and many of his
students. Work with Tradescantia became feasible after Edgar
Anderson straightened out the ecology and Sax took advantage of the
small number of chromosomes easily visible under the microscope. As
a matter of fact. this development is seen as the foundation for
the quantitative analysis of radiation effects on chromosomes.
During the 50 years since then.- more refined studies have been
initiated. The study of cytogenetic mechanisms has become an
important tool for the recognition of the effects of environmental
factors on all liv ing systems and has made SCE studies possible.
One of the most important stages in chromosome research was the
development, in radiation biology, of radiolabeling the chromosome
with tritiated thymidine. This technique. published in 1957 by Dr.
The study of the relationship between environmental pollution and
human health is in its infancy. The number of substances and
mixtures that have been identified in uncontrolled hazardous waste
sites or that have been in advertently released into the
environment is large and data on how thes~ substances are modified
as they interact with one another as they migrate through soil,
air, and water are limited. There are also limits on our un
derstanding of how these substances may be ingested, inhaled, or
absorbed by people. The complexity of possible interactions between
biological, chemical, and physical components in a given
environment makes it virtually impossible to evaluate the potential
for adverse biological effects ade quately in the laboratory.
Other, more comprehensive methods which provide realistic and
interpretable results must be used. Many scientists believe that
humans represent the ultimate sentinel species of a toxic exposure
re sUlting from environmental pollution, however such exposures may
also se verely impact environmental health. There exists a wide
variety of organ isms in the natural environment that could be used
to provide an early warning for potential human health effects as
well as to indicate adverse ecological effects. The issue of
effective utilization of sentinel species for environment al
monitoring is a rapidly developing area of research which has grown
in importance during the last decade.
For at least 40 years there has been a great interest in the
problems created by infectious airborne agents and other toxic sub
stances transported through the air. During the Second World War,
this problem grew out of the very high incidence of upper respira
tory infections appearing in new military recruits who were brought
together in very large, open quarters. As a result, very interest
ing methods were developed to measure these airborne agents, espe
cially bacteria, and some important methods were refined for their
control. These methods primarily concentrated on ultraviolet radia
tion, propylene glycol and other means to reduce the dust in an en
vironment. Because of the specialized circumstances at that time
the whole consideration of airborne particles became prominent.
Now, with the new strides in the recognition of mutagenic and
carcinogenic effects attributed to exposure to airborne chemicals
from today's technology, the problem has again become quite promi
nent. The development of experimental chambers has made it possible
to conduct studies under carefully controlled conditions."
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