1. EFFECTS OF RADIATION ON BIOTA AND SETTING BENCHMARKS Radiation Protection of the Environment (Environment Agency Course, July 2015)

2. Understand how radiation affects biological systems Put effects information into context for wildlife radiation protection Know how a benchmark is derived Be aware of how benchmarks are used in assessments By the end of the presentation and practical you should….

3. Ionization Ionization occurs when energy is sufficient to eject an electron – importance of DNA The radiation emitted from radioactive atoms can be of sufficient energy to cause ionization of other atoms.

4. base loss base change single stand break double stand break interstrand crosslinks OOH H 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

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

6. DNA damage and repair

7. Fate of Mutations Somatic Cells Somatic Cells Germ Cells Germ Cells Decrease in number and quality of gametes Increased embryo lethality Alteration to offspring Cell Death Cell Death Cancer

8.  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 Deleterious mutations Neutral mutations Spread in the population Remove from the population Persist over many generations

9. FREDERICA (www.frederica-online.org)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)

10. Early Mortality premature death of organism Early Mortality premature death of organism Morbidity reduced physical well being including effects on growth and behavior Morbidity reduced 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

11. 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, sublethal effects for chronic, low level exposure to radiation, alone, or mixed with other contaminants

12. Populations are resilient Indirect effects often occur that are unpredictable Blaylock (1969) studies at Oak Ridge DIRECT EFFECT: Increased mortality of fish embryos exposed to 4 mGy / d COMPENSATING MECHANISM: Fish produced larger brood sizes NET RESULT: No effect to population Compensating mechanisms exist

13. Pika LD 50 in captivity: ~ 5.6 Gy LD 50 in the wild: ~ 3.8 Gy (Markham, et al. 1974)

14. 26 April 1986 Exclusion Zone 3,500 km 2 116,000 people relocated Radioactive releases for 10 days

15. 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

16. 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

17. 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

18. Increasing SensitivityDecreasing Sensitivity Large nucleusSmall nucleus Large chromosomesSmall chromosomes Acrocentric chromosomesMetacentric chromosomes Low chromosome numberHigh chromosome number Diploid or haploidHigh polypolid Sexual reproductionAsexual reproduction Long intermitotic timeShort intermitotic time Long dormant periodShort or no dormant period (Sparrow, 1961)

19. minor effects (chromosomal damage; changes in reproduction and physiology) Effects from Short Term Exposures (5 to 60 d) intermediate effects (selective mortality of individuals within a population)

20. IIIIII 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

21. Gy / d Acute adverse effects within 10-km zone Mortality to most sensitive plants and animals Reproductive impacts to many species of biota Dose rates from gamma exposures ranged from 0.02 to 20 Gy / d Dose dominated by short-lived isotopes 99 Mo; 132 Te/I; 133 Xe; 131 I; 140 Ba/La

22. II Decay of short- lived isotopes Radionuclide migration β to δ ~ 6:1 to 30:1 with > 90 % of dose from β

23. III Dose rates are chronic, < 1% of initial 137 Cs and 90 Sr dominate dose Beta to gamma contributions more comparable, depends on bioaccumulation of Cs Indirect effects dominate Genetic effects persist; although some results are controversial

24. 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 controls Morphological mutations 1 to 15 Gy (e.g. leaf gigantism) Hardwoods more radioresistant Evidence of adaptive response

25. Growth and developmental problems Twisted needles Gy / d 0.3 Gy / d Inhibition of photosynthesis, transpiration Short term sterility Chromosome aberrations in meristem cells High mutation rates in wheat due to non-targeted mechanisms

26. 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

27. 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

28. During Fall 1986, rodents population < 2- to 10-fold, dose rates 1 to 30 Gy/d (δ & β) 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

29. ~ 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

30. 4 km N of Reactor 50,000 people Pripyat Abandoned 116,000 people and 60,000 cattle evacuated initially Dozens of towns and villages deserted

31. Przewalski Horses Russian Boar Wolves 48 endangered species listed in the international Red Book of protected animals and plants are now thriving in the Chernobyl Exclusion Zone

32. 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

34. Gy / d 0.000001 IAEA Guidelines 1 & 10 mGy / d PNEDR for ecosystems

35. 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

36. The need for a benchmark...... a retrospective screening model example

37. Fundamental to this approach is the necessity for the dose estimate to be conservative This assures the modeler that the PREDICTED DOSES are LARGER than the REAL DOSES

43. …a BENCHMARK value We need a point of reference; a known value to which we can compare…

44. Benchmarks values are concentrations, doses, or dose rates that are assumed to be safe based on exposure – response information. They represent « safe levels » for the ecosystem Benchmarks are numerical values used to guide risk assessors at various decision points in a tiered approach The derivation of benchmarks needs to be through transparent, scientific reasoning Benchmarks correspond to screening values when they are used in screening tiers

45. No data To few to draw conclusions Some data

48. From literature reviews Earlier numbers derived by expert judgement (different levels of transparency) Later numbers, more quantitative/mathematical Levels of conservatism? Often “maximally exposed individual” not population... NCRP 1991 states use with caution if large number of individuals in a population may be affected

49. i.e. screening values thought to be protective of the structure and function of generic freshwater, marine and terrestrial ecosystems. Adapting approaches used for chemical contaminants to estimate predicted no-effect dose rate (PNEDR)

50. Best-EstimateCentile 5%Centile 95% VertebratesPlantsInvertebrates 5% HDR 5 = 17 µGy/h [2-211] PNEDR=10 µGy/h (SF of 2) EDR 10 and 95%CI: Minimum value per species

51. …a BENCHMARK value We need a point of reference; a known value to which we can compare… 10 μGy/h * 24 h / d = 240 μGy/d = 0.2 mGy /d

52. The PNEDR: – is a basic generic ecosystem screening value – Can be applied to a number of situations requiring environmental and human risk assessment Be aware of: – PNEDR was derived for use only in Tiers 1 and 2 of the ERICA Integrated Approach – Use for incremental dose rates and not total dose rates which include background

53. Marine organisms – 0.6 - 0.9 μGy/h (Hosseini et al., 2010) Freshwater organisms – 0.4 – 0.5 μGy/h (Hosseini et al., 2010) Terrestrial animals and plants – 0.07-0.6 μGy/h (Beresford et al., 2008)

54. Marine organisms – 0.6 - 0.9 μGy/h (Hosseini et al., 2010) Freshwater organisms – 0.4 – 0.5 μGy/h (Hosseini et al., 2010) Terrestrial animals and plants – 0.07-0.6 μGy/h (Beresford et al., 2008)

56. As part of ICRP 108, effects considered No dose ‘limits’ but still need something to compare to – …background – …derived consideration reference levels

57. Derived Consideration Reference Levels – “A band of dose rate within which there is likely to be some chance of deleterious effects of ionising radiation occurring to individuals of that type of RAP (derived from a knowledge of expected biological effects for that type of organism) that, when considered together with other relevant information, can be used as a point of reference to optimise the level of effort expended on environmental protection, dependent upon the overall management objectives and the relevant exposure situation.”

58. DeerRatDuck FrogTroutFlatfish BeeCrab Earthworm Pine tree GrassSeaweed mGy/d Background level

59. Reference Animals and Plants ‘Derived consideration reference levels’ for environmental protection REPRESENTATIVE ORGANISMS Radionuclide intake and external exposure Planned, emergency and existing exposure situations

60. For doses to wildlife, if initial assessment outcome ≥ 1 μGy/hr = more detailed realistic assessment required before regulatory decision made EA must ensure integrity of Natura 2000 Habitat sites – Total dose below 40 μGy/hr (agreed with Natural England) Use Initial Radiological Assessment Tool (IRAT) – Habitats component based on R&D128

61. Range of methods for deriving benchmarks Range of benchmarks proposed Be careful with the wording around the benchmark – What does it reflect? Look for clear, well documented benchmark values Watch this space for further developments!