tom hinton (irsn) ceh lancaster 27th-29th june 2012

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.


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


Free Radicals (unstable molecule that loses one of its electrons)


DNA damage and repair


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


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


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)


http://www.frederica-online.org/

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


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%


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


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:


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


26 April 1986

Contaminated 200,000 km2

350,000 people relocated

Radioactive releases for 10 days

CHERNOBYL


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


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


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


• Before Chernobyl

• Chernobyl overview• temporal aspects• general effects to major classes of organisms • indirect effects – confounding variables

• Possible reasons for controversy


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…


• 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)


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)


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


• 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


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


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


0.001 0.01 0.1 1 10 100 1000Gy / d

• Dose rates from gammaexposures ranged from

0.02 to 20 Gy / d


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


Second Phase

0

20

40

60

80

100

0.1 1 10 100


Rel

ati

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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


Third and Continuing Phase

0

20

40

60

80

100

0.1 1 10 100


Rel

ati

ve

Co

ntr

ibu

tio

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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


• 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


• 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


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


• ~ 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


Rel

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%)

III


• 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


• 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


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.


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


Wormwood Forest: A Natural History of

Chernobyl

Mary Mycio


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


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


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


• 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)


Perfluoroctane Sulfonate (PFOS)


• Effects from mixtures of contaminants….

3M Company


• 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


http://www.redcross.org/

In the course of a single generation, we contaminated virtually all of earth’s biological systems with

perfluoroctane sulfonate.


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


tom hinton (irsn) ceh lancaster 27th-29th june 2012

Documents

ukceh risk course

risk of hereditary effects

cancer risk

radiation responses

effects of radiation

radiation repair of

effects of radiation

risk assessments of