RADIATION ECOLOGY 1045
man on his environment than the atom bomb and nuclear
reactors. Understanding of nearly all pollutant chemicals
in the environment is being enhanced by use of tech-
niques and principles of ecological cycling developed by
radioecologists.CURRENT DEVELOPMENTS IN RADIATION
ECOLOGYThe last several years have witnessed a major decrease of
interest in, and hence support of, research in radiation ecol-
ogy. In the United States the research programs and projects
initiated primarily under the Atomic Energy Commission
(AEC) have been mostly dismantled. The rationale behind
these policy shifts is difficult to comprehend; however, it
seems to have been associated with a perception that most
of the scientific challenges associated with the ecological
aspects of radiation are either sufficiently understood or can
contribute little to those practical issues related to radia-
tion protection that are still of concern. Despite this ratio-
nale, there has been little change in the long-standing public
fear of ionizing radiation and its potential consequences. In
addition, the recent major accident at the Russian nuclear
power station at Chernobyl (1986), in which 50–100 Mci
was released into the environment, not only raised or exacer-
bated fears in those public sectors already concerned about
radiation problems associated with nuclear power but also
served to galvanize resistance in large groups (e.g., the Soviet
public and other East European populations) that hitherto
had either accepted nuclear power or manifested little if any
public resistance.
The Chernobyl accident underscored both the inef-
fectuality of political boundaries against environmental
contamination and the role of food chains, both natural
and agricultural, in exposing humans and other organisms
to potentially harmful levels of radionuclides. Likewise,
Chernobyl focused interest on the direct consequences of
radiation on ecosystems in the zones of high contamination
(within a radius of 18 km of the reactor site). The release of
large quantities of^134 Cs and^137 Cs resulted in the contamina-
tion of lakes, streams, and forests in the path of the plume.
The need to understand the rates of transfer and patterns of
bioaccumulation of these radionuclides in different ecologi-
cal pathways became manifest in many European countries
located thousands of kilometers away from the reactor. In
Sweden, for example, high concentrations of^137 Cs were
found in reindeer and moose (1,000 to 10,000 Bq/kg) and
in several species of freshwater fish. The relatively rapid
buildup of radionuclides in these organisms was the result
of processes which can affect both the rate and extent of bio-
accumulation in food chains. Thus the Chernobyl accident
has emphasized an increased need for additional research in
radiation ecology.
Food chains are the ecological pathways by which many
substances are moved in terrestrial and freshwater envi-
ronments. In the case of radionuclides, these pathways are
important in the assessment of radiation exposure to criticalpopulation subgroups and human populations. Until recently
the uptake and transfer coefficients used in regulatory models
were mainly generic default values intended for use in lieu
of site-specific information. The Chernobyl accident demon-
strated the importance of and need for geographic-specific
data on individual radionuclide behavior in terrestrial and
fresh-water pathways.
Unlike the United States, most other countries are
involved in extensive radioecological research. This
research is aimed at obtaining data for predicting exposure
resulting from transport of radionuclides in agricultural
food chains. The processes of interest in terrestrial envi-
ronments are those involving atmospheric deposition onto
soils and vegetation; resuspension and leaching from these
surfaces; uptake from soils by the edible portions of vegeta-
tion; and transfer into meat, milk, and other animal products
utilized by humans. In the aquatic environment the key pro-
cesses involve the bioaccumulation of radionuclides from
sediments, water, and algae into the edible components of
aquatic biota.
The assessment of the environmental and health impacts
resulting from radiation exposure is dependent on the use
of mathematical models, which, like all other models, are
prone to uncertainty. The best method for evaluating uncer-
tainties in the predictions of dose-assessment models is to
test predictions against data obtained under real-world con-
ditions. The large extent of contamination following the
Chernobyl accident has provided exactly this type of oppor-
tunity. Currently an international cooperative effort known as
BIOMOVS (BIOspheric MOdel Validation Study) is under
way to test models designed for the calculation of environ-
mental transfer and bioaccumulation of radionuclides and
other trace substances. More than 20 assessment models are
now being tested against data collected from numerous sites
throughout the Northern Hemisphere. Upon completion of
the initial model testing effort of the BIOMOVS project,
additional long-term testing is being planned and organized
by the International Atomic Energy Agency (IAEA).
Another issue of concern that has not received research
attention recently in the United States in the direct effect
of ionizing radiation on populations and communities of
organisms. This issue invariably arises whenever there is a
nuclear-related incident. In the case of the Chernobyl acci-
dent, radiation exposures in the immediate vicinity of the
reactor resulted in 28 human fatalities, with a larger number
or persons (209) suffering varying degrees of radiation sick-
ness. Pine forests within several kilometers of the reactor site
received sufficient contamination to result in an accumulated
dose of more than 1000 rads. According to Soviet reports,
pronounced morphological damage to pine foliage was vis-
ible within 5 months after the accident in the zones where
the doses ranged from 300 to 1000 rads. Lethal effects in the
1000 rad zone were also manifest by this time, and by winter
(7 months postaccident) 400 ha of forest was destroyed. An
ecological preserve has been established in one of the natu-
ral areas subjected to high levels of radionuclide contamina-
tion. The Soviet government has announced its intention to
carry out long-term radioecological observations and studiesC018_001_r03.indd 1045C018_001_r03.indd 1045 11/18/2005 11:04:28 AM11/18/2005 11:04:28 AM