Effects of Radiation on Biota Tom Hinton IRSN

Effects of Radiation on Biota Tom Hinton (IRSN) CEH Lancaster 27 th-29 th June 2012

OBJECTIVES To have a fundamental, introductory understanding of: • 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 UK-CEH Risk Course; June 2012 2

Ionization The radiation emitted from radioactive atoms can be of sufficient energy to cause ionization of other atoms. Ionization occurs when energy is sufficient to eject an electron UK-CEH Risk Course; June 2012 3

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 UK-CEH Risk Course; June and 2012 Schultz, 1982) 4

Different kinds of DNA damage induced by γ-radiation per 0. 01 Gy base loss base change H OH single stand break double stand break interstrand crosslinks UK-CEHJ. Risk Course; June 2012 Feinendegen, Pollycove. Nucl. Medicine. 2001. V. 42. p. 17 N-27 N 5

Free Radicals (unstable molecule that loses one of its electrons) UK-CEH Risk Course; June 2012 6

DNA damage and repair UK-CEH Risk Course; June 2012 7

Fate of Mutations Somatic Cells Cell Death Cancer Germ Cells Decrease in number and quality of gametes UK-CEH Risk Course; June 2012 Increased embryo lethality Alteration to offspring 8

Fate of mutations in non-human biota For humans, risk of hereditary effects in offspring of exposed v individuals is about 10% of the cancer risk to the exposed parents (UNSCEAR, 2001) v For non-human biota the risk of hereditary effects is unknown Cell Confer a selective advantage Spread in the population Deleterious mutations Remove from the population Mutation Neutral mutations UK-CEH Risk Course; June 2012 Persist over many generations 9

Knowledge of ionising radiation’s effect on wildlife is the basis for the derivation of radiological risk benchmarks UK-CEH Risk Course; June 2012 10

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) www. ceh. ac. uk/PROTECT UK-CEH Risk Course; June 2012 11

Radiation Effects on Non. Human Biota Early Mortality premature death of organism Morbidity reduced physical well being including effects on growth and behavior Reproduction is thought to be a more sensitive effect than mortality Reproductive Success reduced fertility and fecundity UK-CEH Risk Course; June 2012 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 12

41 studies that included 28 species and 44 toxicants Population Growth Rate (Forbes & Calow, 1999) 52% Time to reach sexual maturity Mortality of juveniles Reduction in number of offspring No correlation 31% Mortality of adults UK-CEH Risk Course; June 2012 13

Fundamental Differences In Human and Ecological Risk Analyses Type Human Ecological Unit of Observation individual varies population, community, ecosystem Endpoint lifetime cancer risk Dose-Response relationships established varies not established > mortality, < fecundity, sublethal effects UK-CEH Risk Course; June 2012 for chronic, low level exposure to radiation, alone, or mixed with other contaminants 14

Predicting radiological effects to wildlife is complicated because: Populations are resilient Compensating mechanisms exist Blaylock (1969) studies at Oak Ridge DIRECT EFFECT: Increased mortality of fish embryos exposed to 4 m. Gy / d COMPENSATING MECHANISM: Fish produced larger brood sizes NET RESULT: No effect to population Indirect effects often occur that are unpredictable UK-CEH Risk Course; June 2012 15

Responses of Animals to Radiation Are Complicated by: - other stresses (chemical, physical, biological) - life cycle stage and physiological condition - environmental variables Pika LD 50 in captivity: ~ 5. 6 Gy LD 50 in the wild: ~ 3. 8 Gy UK-CEH Risk Course; June 2012 (Markham, et al. 1974) 16

CHERNOBYL 26 April 1986 Radioactive releases for 10 days Contaminated 200, 000 km 2 350, 000 people relocated UK-CEH Risk Course; June 2012 17

Wildlife Defies Chernobyl Radiation By Stephen Mulvey BBC News 20 April 2006 “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”. Sergey Gaschak UK-CEH Risk Course; June 2012 18

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 UK-CEH Risk Course; June 2012 19

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 UK-CEH Risk Course; June 2012 20

• Before Chernobyl • Chernobyl overview • temporal aspects • general effects to major classes of organisms • indirect effects – confounding variables • Possible reasons for controversy UK-CEH Risk Course; June 2012 21

Factors Influencing the Sensitivity of Plants to Radiation Increasing Sensitivity Decreasing Sensitivity Large nucleus Large chromosomes Acrocentric chromosomes Small nucleus Small chromosomes Metacentric chromosomes Low chromosome number Diploid or haploid Sexual reproduction Long intermitotic time Long dormant period High chromosome number High polypolid Asexual reproduction Short intermitotic time Short or no dormant period UK-CEH Risk Course; June 2012 (Sparrow, 1961) 22

Pre-Chernobyl… Lethal Acute Dose Ranges (Data from: Sparrow et al 1967) UK-CEH Risk Course; June 2012 23

Pre-Chernobyl… Effects from Short Term Exposures (5 to 60 d) • minor effects (chromosomal damage; changes in reproduction and physiology) • intermediate effects (selective mortality of individuals within a population) UK-CEH Risk Course; June 2012 24

DOSE (Gy) to DOSE RATE (Gy / d) CONVERSION (5 to 60 d) x/10 Gy / d UK-CEH Risk Course; June 2012 25

Within Chernobyl’s 30 -km zone • 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 I II UK-CEH Risk Course; June 2012 III 26

First 20 to 30 days • Severe effects to biota • Gamma exposure dose rates were > 20 Gy / d • Dominated by short-lived isotopes 99 Mo; 132 Te/I; 133 Xe; 131 I; 140 Ba/La • High dose to thyroids from iodine I UK-CEH Risk Course; June 2012 27

Air Exposure Rates on 26 April 1986 0. 02 Gy /d 0. 2 Gy /d 20 Gy /d (1 R / h ~ 0. 2 Gy / d; UNSCEAR 2000) UK-CEH Risk Course; June 2012 28

• Dose rates from gamma exposures ranged from 0. 02 to 20 Gy / d UK-CEH Risk Course; June 2012 29

First Phase • Acute adverse effects within 10 -km zone • Mortality to most sensitive plants and animals • Reproductive impacts to many species of biota Gy / d UK-CEH Risk Course; June 2012 30

Second Phase • Decay of short-lived isotopes • Radionuclide migration • β to δ ~ 6: 1 to 30: 1 with > 90 % of dose from β II UK-CEH Risk Course; June 2012 31

Third and Continuing Phase • Dose rates are chronic, < 1% of initial • Beta to gamma contributions more comparable, depends on bioaccumulation of Cs • 137 Cs and 90 Sr dominate dose III • Indirect effects dominate • Genetic effects persist; although some results are controversial UK-CEH Risk Course; June 2012 32

General Effects to Plants • Morphological mutations 1 to 15 Gy (e. g. leaf gigantism) • Hardwoods more radioresistant • Shift in ecosystem structure: Deceased pine stands were replaced by grasses, with a slow invasion of hardwoods • Genetic effects extended in time 1993, pines of 5 to 15 Gy had 8 X greater cytogentic damage than • Evidence of adaptive response UK-CEH Risk Course; June 2012 33 controls

General Effects to Plants 0. 3 Gy / d • Growth and developmental problems • Inhibition of photosynthesis, transpiration • Chromosome aberrations in meristem cells • Short term sterility • High mutation rates in wheat due to nontargeted mechanisms Twisted needles Gy / d UK-CEH Risk Course; June 2012 34

General Effects to Rodents • During Fall 1986, rodents population < 2 - to 10 -fold, dose rates 1 to 30 Gy/d (δ & β) • At ~ 0. 1 Gy/d temporary infertility, reduced testes mass • Increased mortality of embryos • Dose-rate dependent increase in reciprocal translocations • Numbers of mice recovered within 3 years (immigration), but cytogenetic effects persisted UK-CEH Risk Course; June 2012 Gy / d 35

Effects Data from Rodents Collected in Phase III Are Ambiguous and Controversial From virtually no effect…. … to significantly elevated mutation rates • ~ 30 to 40 generations post-accident • lower dose rates • chronic exposures III • inadequate dosimetry • sample size and technique sensitivity • indirect effects (immigration) • interpretation of results from new methods (microsatellites) UK-CEH Risk Course; June 2012 36

General Effects to Soil Invertebrates • 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 UK-CEH Risk Course; June 2012 37

General Effects to Soil Invertebrates • Dose and effects to invertebrates in forest litter were 3 - to 10 fold higher than those in agricultural soils • 30 Gy altered community structure (species diversity) for 2. 5 years UK-CEH Risk Course; June 2012 38

Indirect Effects of Human Abandonment Pripyat Abandoned 4 km N of Reactor 50, 000 people 135, 000 people and 35, 000 cattle evacuated Dozens of towns and villages deserted. UK-CEH Risk Course; June 2012 39

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 Russian Boar Wolves Przewalski Horses UK-CEH Risk Course; June 2012 40

Wormwood Forest: A Natural History of Chernobyl Mary Mycio UK-CEH Risk Course; June 2012 41

Barn Swallows at Chernobyl • partial albinism as a phenotypic marker for mutations ( ↑ 10 x) • 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 UK-CEH Risk Course; June 2012 42

UK-CEH Risk Course; June 2012 43

IAEA Guidelines 1 & 10 m. Gy / d 0. 000001 Gy / d UK-CEH Risk Course; June 2012 PNEDR for ecosystems 44

Potential Causes for Controversial Data • Poor dosimetry can cause misinterpretation of data • Spatial heterogeneity of exposure; free-ranging wildlife • Confounding variables and indirect effects • Lack of analogous controls • Questionable statistical analyses • What constitutes a “significant effect”? ? • Adaptation to generations of chronic exposure UK-CEH Risk Course; June 2012 45

Most research is not directly relevant to responses in nature Data Plentiful Data Scarce but Least Relevant but Most Relevant Individual response Mortality Acute exposure External gamma Laboratory Short-term Population response Reproduction Chronic exposure Multiple exposure route Field Long-term UK-CEH Risk Course; June 2012 46

Questions remaining to be answered… • What is the extent of inherited, transgenerational effects from chronic, low-level irradiation? • What is the significance of molecular effects to individuals and populations? • STAR Network of Excellence in Radioecology identified long term research needs in their Strategic Research Agenda (www. star-radioecology. org) UK-CEH Risk Course; June 2012 47

• Effects from mixtures of contaminants…. Perfluoroctane Sulfonate (PFOS) UK-CEH Risk Course; June 2012 48

3 M Company UK-CEH Risk Course; June 2012 49

• 760 random samples from across the U. S. PFOS was in every sample • 600 mores samples from the American Red Cross PFOS was in every sample • 1500 samples from Belgium, the Netherlands and Germany PFOS was in every sample but two Alarmed, 3 M notified EPA, and in 2000, 3 M stopped production of PFOS UK-CEH Risk Course; June 2012 50

UK-CEH Risk Course; June 2012 51

In the course of a single generation, we contaminated virtually all of earth’s biological systems with perfluoroctane sulfonate. UK-CEH Risk Course; June 2012 52

Radiation 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 UK-CEH Risk Course; June 2012 Metals Organics 53