tom hinton (irsn) ceh lancaster 27th-29th june 2012
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Effects of Radiation on Biota
Tom Hinton (IRSN)
CEH Lancaster 27th-29th June 2012
OBJECTIVES
• radioactive decay and ionization as it relates to effects of radiation
• DNA’s role as the primary target for the induction of biological effects
• the broad similarities in radiation responses among organisms
• the wide variation in responses among organisms
• free radicals and their role in the biological effects from radiation
• repair of damage from radiation
• mis-repair of damage and the fate of mutations within a population of organisms
• fundamental differences in human versus ecological risk analyses from the perspective of radiation effects
• a general idea of the state of knowledge about radiation effects and some of the major data gaps that need to be addressed
To have a fundamental, introductory understanding of:
2UK-CEH Risk Course; June 2012
Ionization
Ionization occurs when energy is sufficient to eject an electron
The radiation emitted from radioactive atoms can be of sufficient energy to cause ionization of other atoms.
3UK-CEH Risk Course; June 2012
DNA is the primary target for the induction of biological effects from radiation in ALL living organisms
Broad similarities in radiation responses for different organisms……and yet, wide differences in radiation sensitivity
(Whicker and Schultz, 1982) 4UK-CEH Risk Course; June 2012
base lossbase change
single stand break
double stand break
interstrand crosslinks
O OHH
H
Feinendegen, Pollycove. J. Nucl. Medicine. 2001. V.42. p. 17N-27N
Different kinds of DNA damage induced by γ-radiation per 0.01 Gy
5UK-CEH Risk Course; June 2012
Free Radicals (unstable molecule that loses one of its electrons)
6UK-CEH Risk Course; June 2012
DNA damage and repair
7UK-CEH Risk Course; June 2012
Fate of MutationsFate of Mutations
SomaticCells
SomaticCells
GermCells
GermCells
Decrease in number
and quality of gametes
Decrease in number
and quality of gametes
Increased
embryo lethality
Increased
embryo lethality
Alteration to
offspring
Alteration to
offspringCell
DeathCell
DeathCancerCancer
8UK-CEH Risk Course; June 2012
For humans, risk of hereditary effects in offspring of exposed individuals is about 10% of the cancer risk to the exposed
parents (UNSCEAR, 2001)
For non-human biota the risk of hereditary effects is unknown
Fate of mutations in non-human biota
Mutation
Cell
Confer a selective
advantage
Confer a selective
advantage
Deleterious
mutations
Deleterious
mutations
Neutral mutationsNeutral
mutations
Spread in the
population
Spread in the
population
Remove from the
population
Remove from the
population
Persist over many
generations
Persist over many
generations9UK-CEH Risk Course; June 2012
Knowledge of ionising radiation’s effect on wildlife is the basis for the derivation
of radiological risk benchmarks
10UK-CEH Risk Course; June 2012
www.ceh.ac.uk/PROTECT
Data Base of Knowledge on Effects of Radiation Exposure on Biota
FREDERICA (www.frederica-online.org)
– An online database of literature data to help summarise dose-effect relationships
– FREDERICA can be used on its own; or in conjunction with the ERICA assessment tool (for conducting risk assessments of wildlife exposed to ionising radiation)
(> 1500 references; 26 000 data entries)
11UK-CEH Risk Course; June 2012
Radiation Effects on Non-Human Biota
Early Mortalitypremature death of
organism
Early Mortalitypremature death of
organism
Morbidityreduced physical well being including effects
on growth and behavior
Morbidityreduced physical well being including effects
on growth and behavior
Reproductive Success
reduced fertility and fecundity
Reproductive Success
reduced fertility and fecundity
These categories of radiation effects are similar to the endpoints that are often used for risk assessments of other environmental stressors, and are relevant to the needs of nature conservation and other forms of environmental protection
Reproduction is thought to be a more sensitive effect than mortality
12UK-CEH Risk Course; June 2012
Mortality of juveniles
Reduction in number of offspring
Time to reach sexual maturity
Mortality of adults
Population Growth Rate
41 studies that included 28 species and 44 toxicants(Forbes & Calow, 1999)
52%
No correlation
31%
13UK-CEH Risk Course; June 2012
Fundamental Differences In Human and Ecological Risk Analyses
Type Unit of Observation Endpoint Dose-Response Human individual lifetime cancer relationships risk established
Ecological varies varies not established population,
community,ecosystem
> mortality,
< fecundity,sublethaleffects
for chronic,low level exposure
to radiation, alone, ormixed with other
contaminants
14UK-CEH Risk Course; June 2012
Populations are resilient
Indirect effects often occur that are unpredictable
Blaylock (1969) studies at Oak RidgeDIRECT EFFECT: Increased mortality of fish embryos exposed to 4 mGy / dCOMPENSATING MECHANISM: Fish produced larger brood sizesNET RESULT: No effect to population
Compensating mechanisms exist
Predicting radiological effects to wildlife is complicated because:
15UK-CEH Risk Course; June 2012
Pika
LD50 in captivity: ~ 5.6 GyLD50 in the wild: ~ 3.8 Gy
(Markham, et al. 1974)
Responses of Animals to Radiation Are Complicated by:
- other stresses (chemical, physical, biological)
- life cycle stage and physiological condition
- environmental variables
16UK-CEH Risk Course; June 2012
26 April 1986
Contaminated 200,000 km2
350,000 people relocated
Radioactive releases for 10 days
CHERNOBYL
17UK-CEH Risk Course; June 2012
Wildlife Defies Chernobyl Radiation
By Stephen Mulvey BBC News
“It contains some of the most contaminated land in the world, yet it has become a haven for wildlife - a nature reserve in all but name”.
20 April 2006
Sergey Gaschak
18UK-CEH Risk Course; June 2012
Chernobyl ‘Shows Insect Decline'
By Victoria Gill,Science Reporter, BBC NEWS
18 March 2009
“Two decades after the explosion at the Chernobyl nuclear power plant, radiation is still causing a reduction in the numbers of insects and spiders”.
A. Moller and T. Mousseau
19UK-CEH Risk Course; June 2012
Pre-Chernobyl…
• wealth of data about the biological effects of radiation on plants and animals
• early data came from…• laboratory exposures• accidents (Kyshtym, 1957)• areas of naturally high background• nuclear weapons fallout • large-scale field irradiators
20UK-CEH Risk Course; June 2012
• Before Chernobyl
• Chernobyl overview• temporal aspects• general effects to major classes of organisms • indirect effects – confounding variables
• Possible reasons for controversy
21UK-CEH Risk Course; June 2012
Increasing Sensitivity Decreasing SensitivityLarge nucleus Small nucleus
Large chromosomes Small chromosomes
Acrocentric chromosomes Metacentric chromosomes
Low chromosome number High chromosome number
Diploid or haploid High polypolid
Sexual reproduction Asexual reproduction
Long intermitotic time Short intermitotic time
Long dormant period Short or no dormant period
Factors Influencing the Sensitivity of Plants to Radiation
(Sparrow, 1961) 22UK-CEH Risk Course; June 2012
Lethal Acute Dose Ranges (Data from: Sparrow et al 1967)
Pre-Chernobyl…
23UK-CEH Risk Course; June 2012
• minor effects (chromosomal damage; changes in reproduction and physiology)
Effects from Short Term Exposures (5 to 60 d)
Pre-Chernobyl…
• intermediate effects (selective mortality of individuals within a
population)
24UK-CEH Risk Course; June 2012
0.001 0.01 0.1 1 10 100 1000Gy / d
x/10
DOSE (Gy) to DOSE RATE (Gy / d) CONVERSION
(5 to 60 d)
25UK-CEH Risk Course; June 2012
Within Chernobyl’s 30-km zone
0
20
40
60
80
100
0.1 1 10 100
months post accident
Rel
ati
ve
Co
ntr
ibu
tio
n
D
ose
(%
)
I II III
• Environmental effects were specific to 3 distinct time periods
• Biota were exposed to a diverse group of radioisotopes
• Tremendous heterogeneity and variability (in all parameters)
• Accident occurred at a period of peak sensitivity for many biota
26UK-CEH Risk Course; June 2012
• Severe effects to biota
• High dose to thyroids from iodine
First 20 to 30 days
0
20
40
60
80
100
0.1 1 10 100
months post accident
Rel
ati
ve
Co
ntr
ibu
tio
n
D
ose
(%
)
I
• Gamma exposure dose rates were > 20 Gy / d
• Dominated by short-lived isotopes 99Mo; 132Te/I; 133Xe; 131I; 140Ba/La
27UK-CEH Risk Course; June 2012
100C O O L IN G P O N D
1 km
T O W N O F P R IP YAT
R E A C T O R1
10
100
100
1
0 .1
R IV E R P R IP YAT
20 Gy /d2 Gy /d
0.02 Gy /d
0.2 Gy /d
(1 R / h ~ 0.2 Gy / d; UNSCEAR 2000)
Air Exposure Rates on 26 April 1986
28UK-CEH Risk Course; June 2012
0.001 0.01 0.1 1 10 100 1000Gy / d
• Dose rates from gammaexposures ranged from
0.02 to 20 Gy / d
29UK-CEH Risk Course; June 2012
0.001 0.01 0.1 1 10 100 1000Gy / d
• Acute adverse effects within 10-km zone
• Mortality to most sensitive plants and animals• Reproductive impacts to
many species of biota
First Phase
30UK-CEH Risk Course; June 2012
Second Phase
0
20
40
60
80
100
0.1 1 10 100
months post accident
Rel
ati
ve
Co
ntr
ibu
tio
n
Do
se (
%)
II
• Decay of short-lived isotopes
• Radionuclide migration
• β to δ ~ 6:1 to 30:1 with > 90 % of dose from β
31UK-CEH Risk Course; June 2012
Third and Continuing Phase
0
20
40
60
80
100
0.1 1 10 100
months post accident
Rel
ati
ve
Co
ntr
ibu
tio
n
Do
se (
%)
III
• Dose rates are chronic, < 1% of initial
• 137Cs and 90Sr dominate dose
• Beta to gamma contributions more comparable, depends on bioaccumulation of Cs
• Indirect effects dominate
• Genetic effects persist; although some results are controversial
32UK-CEH Risk Course; June 2012
• Shift in ecosystem structure: Deceased pine stands were replaced by grasses, with a slow invasion of hardwoods
• Genetic effects extended in time1993, pines of 5 to 15 Gy had 8 X greater cytogentic damage than controls
General Effects to Plants
• Morphological mutations 1 to 15 Gy (e.g. leaf gigantism)
• Hardwoods more radioresistant
• Evidence of adaptive response
33UK-CEH Risk Course; June 2012
• Growth and developmental problems
Twisted needles
0.001 0.01 0.1 1 10 100 1000
Gy / d
0.3 Gy / dGeneral Effects to Plants
• Inhibition of photosynthesis, transpiration
• Short term sterility
• Chromosome aberrations in meristem cells
• High mutation rates in wheat due to non-targeted mechanisms
34UK-CEH Risk Course; June 2012
General Effects to Rodents
• During Fall 1986, rodents population < 2- to 10-fold, dose rates 1 to 30 Gy/d (δ & β)
0.001 0.01 0.1 1 10 100 1000
Gy / d
• Dose-rate dependent increase in reciprocal translocations
• Increased mortality of embryos
• Numbers of mice recovered within 3 years (immigration), but cytogenetic effects persisted
• At ~ 0.1 Gy/d temporary infertility, reduced testes mass
35UK-CEH Risk Course; June 2012
• ~ 30 to 40 generations post-accident • lower dose rates • chronic exposures• inadequate dosimetry • sample size and technique sensitivity• indirect effects (immigration)• interpretation of results from new
methods (microsatellites)
From virtually no effect….… to significantly elevated mutation rates
Effects Data from RodentsCollected in Phase III Are
Ambiguous and Controversial
0
20
40
60
80
100
0.1 1 10 100
months post accident
Rel
ati
ve
Co
ntr
ibu
tio
n
Do
se (
%)
III
36UK-CEH Risk Course; June 2012
• 60 to 90% of initial contamination captured by plant canopies
• Majority washed off to soil and litter within several weeks
• Populations of soil invertebrates reduced 30-fold, reproduction strongly impacted
General Effects to Soil Invertebrates
37UK-CEH Risk Course; June 2012
• 30 Gy altered community structure (species diversity) for 2.5 years
• Dose and effects to invertebrates in forest litter were 3- to 10-fold higher than those in
agricultural soils
General Effects to Soil Invertebrates
38UK-CEH Risk Course; June 2012
4 km N of Reactor50,000 people
PripyatAbandoned
Indirect Effects of Human Abandonment
135,000 people and 35,000 cattle evacuated
Dozens of towns and villages deserted.
39UK-CEH Risk Course; June 2012
Przewalski Horses
Russian Boar
Wolves
With the removal of humans, wildlife around Chernobyl are
flourishing
48 endangered species listed in the international Red Book of protected animals and plants are now thriving in the Chernobyl Exclusion Zone
40UK-CEH Risk Course; June 2012
Wormwood Forest: A Natural History of
Chernobyl
Mary Mycio
41UK-CEH Risk Course; June 2012
Barn Swallows at Chernobyl• partial albinism as a phenotypic
marker for mutations ( ↑ 10x)• carotenoids used for free-radical
scavenging…rather than plumage coloration
• reduced levels of antioxidants in blood
• increase in abnormal sperm • elevated mutation rates in microsats• partial albinism correlated to reduced
mating success• clutch size, brood size and hatching
success reduced
42UK-CEH Risk Course; June 2012
43UK-CEH Risk Course; June 2012
0.001 0.01 0.1 1 10 100 1000Gy / d
d
Gy
Gy
Gyx
d
hx
h
Gy0000024.0
10241.0
6
0.000001
IAEA Guidelines1 & 10 mGy / d
PNEDR for ecosystems44UK-CEH Risk Course; June 2012
• Poor dosimetry can cause misinterpretation of data
• Spatial heterogeneity of exposure; free-ranging wildlife
• Confounding variables and indirect effects
• Questionable statistical analyses
• Lack of analogous controls
• What constitutes a “significant effect”??
• Adaptation to generations of chronic exposure
Potential Causes for Controversial Data
45UK-CEH Risk Course; June 2012
Most research is not directly relevant to responses in nature
Data Scarcebut
Most Relevant
Individual response Population responseMortality ReproductionAcute exposure Chronic exposureExternal gamma Multiple exposure routeLaboratory FieldShort-term Long-term
Data Plentiful but
Least Relevant
46UK-CEH Risk Course; June 2012
• What is the extent of inherited, transgenerational effects from chronic, low-level irradiation?
• What is the significance of molecular effects to individuals and populations?
Questions remaining to be answered…
• STAR Network of Excellence in Radioecology identified long term research needs in their Strategic
Research Agenda (www.star-radioecology.org)
47UK-CEH Risk Course; June 2012
Perfluoroctane Sulfonate (PFOS)
48UK-CEH Risk Course; June 2012
• Effects from mixtures of contaminants….
3M Company
49UK-CEH Risk Course; June 2012
• 760 random samples from across the U.S.
• 600 mores samples from the American Red Cross
PFOS was in every sample
PFOS was in every sample
• 1500 samples from Belgium, the Netherlands and Germany
PFOS was in every sample but two
Alarmed, 3M notified EPA, and in 2000,3M stopped production of PFOS
50UK-CEH Risk Course; June 2012
51UK-CEH Risk Course; June 2012
In the course of a single generation, we contaminated virtually all of earth’s biological systems with
perfluoroctane sulfonate.
52UK-CEH Risk Course; June 2012
Focusing on a single type of stressor, or on multiple stressors in isolation from others, is likely inadequate to describe the actual threats to individuals or populations
Metals
Radiation
Organics
53UK-CEH Risk Course; June 2012
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