Assessing the Human Health and Ecological Risk of Tritium Associated with Vermont Yankee

1
Assessing the Human Health and Ecological Risk of
Tritium Associated with Vermont Yankee

• Brooke Churas, Allison Rapp, Kacy Roeder, Natasha
  Yandow

2
Background Information

• What is tritium? - Radioactive isotope of
  hydrogen - Low energy beta emitter
• - Same physical, chemical, pharmalogical
  properties as hydrogen
• Where does tritium come from?
• - Naturally present in the environment in small
  amounts as
• Tritiated water (HTO) Gaseous tritium
  (HT) Organically bound tritium (OBT)
• - Byproduct of nuclear fission
• What are the regulatory limits on tritium?
• - The EPA sets limits on tritium in drinking
  water at 20,000 picocuries per liter

http//i133.photobucket.com/albums/q80/Oregon_Suns
et/Ball20HydroCarbon20Chrono/IMG_7753.jpg
3
Understanding Units

• 1 curie amount of material that will produce
  3.7 x 1010 nuclear decays per second.
• 1 becquerel amount of material which will
  produce 1 nuclear decay per second.
• 1 curie 3.7 x 1010 becquerels.
• 1 picocurie 1x10-12 curies
• 1 Sievert 100 Rem

http//hyperphysics.phy-astr.gsu.edu/HBASE/nuclear
/radrisk.html
4
Tritium and Vermont Yankee Department of Health
Timeline

• January 7, 2010 tritium contamination
  reported
• February 14, 2010- major source of tritium
  leak was identified
• Soil and water testing confirm pathway of
  contamination through the discovery of cobalt-60,
  manganese-54, zinc-65 and cesium-137
• Tritium concentrations have been decreasing in
  samples from groundwater monitoring wells,
  confirming that the leak has been stopped.
• Increase in frequency and number of water and
  environmental samples
• Contaminated groundwater found to move west to
  east into the Connecticut River.
• March- Rigorous monitoring continues
• April- new groundwater well in service
• Continued testing shows no tritium in excess of
  the lower limit for detection

(Vermont Department Health 2010)
5
Most recent well results in (pCi/l) or below the
lower level of detection (ltLLD).
GZ-1 ltLLD GZ-2 ltLLD GZ-3 52,000 GZ-4 2,400
GZ-5 ltLLD GZ-6 ltLLD GZ-7 757,000GZ-8 No
sample dry well GZ-9 ltLLD GZ-10 ltLLD GZ-11
750 GZ-12 267,000 GZ-13S ltLLD GZ-13D 1,200
GZ-14S 258,000 GZ-14D ltLLD GZ-15 710,000
GZ-16 ltLLD GZ-17 ltLLD GZ-18 no well yet
GZ-19S ltLLD GZ-19D ltLLD GZ-20 130,000
GZ-21 2.028 million
(Vermont Department Health 2010)
6
Goal
To combine evidence of the health impacts of
tritium with case studies and current knowledge
pertaining to the Vermont Yankee controversy in
order to provide a risk assessment of the Vermont
Yankee tritium leak to human and environmental
health.
7
Objectives

• Compare case studies with the situation at
  Vermont Yankee
• Use lab studies to assess health effects of
  tritium on human and non-human organisms
• Study biological pathways of tritium in plants
  and in the human body
• Utilize information given during interviews with
  State Toxicologist Bill Bress, Radiological
  Health Chief Bill Irwin
• Present key recommendations regarding Vermont
  Yankee while accounting for uncertainties

8
Tritium Sources

• Natural tritium is created at a rate of 0.15-0.2
  kg/yr
• Nuclear sources contribute 0.06 kg/yr
• Atmospheric weapon tests totaled 560 kg by 1963
  but by 2008 were reduced to about 40 kg

(Boyer 2009)
9
The Tritium Cycle

• Tritium is most commonly found as tritiated
  water, tritiated methane and tritiated molecular
  hydrogen.
• Tritiated water moves through the water cycle as
  normal water does, moving through water bodies,
  atmosphere, soils, groundwater, largely ending up
  in oceans.

http//dnr.wi.gov/org/caer/ce/eek/earth/groundwate
r/images/groundwater.gif
10
Findings Tritium in Plants

• Plant Absorption of Tritium
• Plants take in tritium through their foliage and
  through soil
• Most tritium is quickly released back into the
  atmosphere through transpiration
• Tritium absorbed by a plant will quickly reach
  equilibrium with the tritium in the soil
• Tritium absorption depends on several factors
• Plant type, stage of development, water mass of
  organism, leaf area index
• Stomatal resistance, stomatal gating, stomatal
  gating
• Soil type, soil bacteria
• Meteorological conditions, temperature, relative
  humidity

(Boyer 2009)
11
Findings Tritium in Plants

• Differences in plant absorption of Tritium
• C3 plants absorb more atmospheric tritium during
  the day than at night
• C4 plants typically contain less tritium than C3
  plants
• Lichen, mosses and fungi absorb tritiated water
  rapidly because they lack a cuticle and stomatal
  apparatus

http//img.sparknotes.com/figures/B/b1ab5bb87aee74
a86fdae78ed564e663/stoma.gif
(Boyer 2009)
12
Findings Tritium in Plants

• Boyers Conclusions
• It is assumed that high levels of tritium
  exposure will cause DNA mutations but the
  environmental impacts are minimized by extremely
  limited exposure.
• Based on Boyers findings the environmental
  health impacts of the Vermont Yankee tritium
  leaks will not be significant.

(Boyer 2009)
13
Findings Studies on Rats and Mice

• Yamamoto (1998) orally exposed mice
  continuously throughout their lives
• High (5.0 x 1011 pCi/L 1.6 x 1013 pCi/L) dose
  rates mice died of haematopoietic injury.
• Moderate (1.0 x 1010 pCi/L 2.5 x 1011 pCi/L)
  dose rates the mice died from tumor development.

• A threshold dose rate was determined to be
  12mGy/day.
• The lowest dose rate of radiation that the mice
  were exposed to was 2.35 x 108 pCi/L.
• Vermont Yankee Maximum
• 2.5 x 106 pCi/L (Bress 2010).
• Cancer-causing thresholds in mice are not being
  crossed.

http//www.reptilecity.co.za/catalog/images/MiceWA
.jpg
14
Most recent well results in (pCi/l) or below the
lower level of detection (ltLLD).
GZ-1 ltLLD GZ-2 ltLLD GZ-3 52,000 GZ-4 2,400
GZ-5 ltLLD GZ-6 ltLLD GZ-7 757,000GZ-8 No
sample dry well GZ-9 ltLLD GZ-10 ltLLD GZ-11
750 GZ-12 267,000 GZ-13S ltLLD GZ-13D 1,200
GZ-14S 258,000 GZ-14D ltLLD GZ-15 710,000
GZ-16 ltLLD GZ-17 ltLLD GZ-18 no well yet
GZ-19S ltLLD GZ-19D ltLLD GZ-20 130,000
GZ-21 2.028 million
(Vermont Department Health, 2010)
15
Findings Studies on Rats and Mice
Study by Takeda (2001)

• Effects of chronic ingestion of tritiated food
  is perhaps worse than the effects of chronic
  ingestion of tritiated water.
• Tritium was retained longer in body tissues when
  ingested with food. 

• Greatest risk might come from the ingestion of
  organically bound tritium being consumed as food.

• Bress (2010) assured that ingestion of tritiated
  water is the main concern.

16
Findings Tritium in the Human Body

• Chemical half life 12.35 years
• Biological half life
• 10 days for HTO (90 of uptake)
• 30 days for OBT (10 of uptake)
• 450 days for trace amounts
• Pathways inhalation, ingestion, absorption
  through dermis
• Rate of absorption depends on chemical form
• HTO transferred fastest
• Radiation penetrates 6 ?m, but human epidermis is
  20-100 ?m thick

17
Tritium in the Human Body

• Travels through same biokinetic pathways as
  water/organic compounds
• Uniform distribution as HTO
• Uneven distribution as OBT stored in adipose
  tissue and tissue with high multiplication rate
• Replaces hydrogen in all compounds
• Same physical, chemical, pharmacological
  properties
• 99 excreted as HTO and OBT

18
Tritium in the Human Body

• Effective dose of OBT is 2.3 times higher than
  that of HTO
• Accounts for risk of incorporation into DNA
  (impacts unknown)
• Difficulty of dose measurement
• Low number of contamination cases
• Not highly radioactive
• To have potential impacts, exposure must be 1000
  times the levels found in nature

19
Tritium in the Human Body

• Effects on human body similar to those observed
  in plants
• Once absorbed, it quickly passes through
• Assumptions
• DNA mutations
• Cell damage
• Damage caused from radiation, not from molecule
  itself!
• Unlikely that humans will be exposed to high
  enough concentrations at Vermont Yankee

Exposure to high doses
20
Studies

• Long term effects unknown
• Exposed lymphocytes and marrow cells to HTO
  showed
• Does not increase RBE
• Chromosomal aberrations increased but sister-
  chromatid exchanges did not
• No conclusions about uptake via fruits and
  vegetables should be made

(Tanaka 1994), (Boyer 2009)
21
Impacts of Controlled Releases
Flamanville, Manche, France

• Dose levels account for people living close to
  site
• Adults eating fish within a 500 m radius
• Sunbathing (100 h/yr)
• Swimming (20 h/yr)
• Increased risk for certain groups (ex. fisherman)
• Risk of exposure extremely low

http//www.world-nuclear-news.org/uploadedImages/w
nn/Images/Flamanville203.jpg
(Le Guen 2009)
22
Findings Case Studies at Savannah River Site
(SRS)

• Savannah River Site
• South Carolina
• Not in operation today
• Clean up of past nuclear weapons manufacturing

http//en.wikipedia.org/wiki/FileSavannahRiverSit
e_ISS012-E-16633.jpg
(Little 2007)
23
Findings Case Studies at SRS

• Cragle et al (1998)
• Study
• Mortality of 9,860 white male workers at the SRS,
  1952 to 1980
• Little data on actual tritium doses
• Estimated doses
• 800 employees received gt 0.5 mSv per year
• 1 employee gt 30 mSv per year
• Findings
• Few indications of excess mortality
• 18 prostate cancer deaths versus 21.15 expected
  deaths
• Marginally increasing trend for leukemia at 25
  deaths versus 19.63 expected deaths
• Further analysis

(Little 2007)
24
Findings Case Studies at SRS

• Richardson and Wing (2007)
• Study
• Association between radiation exposure and
  leukemia, 1950-2002
• Doses of tritium, photons, and neutrons were
  estimated
• Findings
• Results into 3 different groups
• Leukemia
• Leukemia excluding chronic lymphocytic leukemia
  (most common type)
• CLL slow progression, affects lymphoid cells
  (white blood cells)
• Myeloid leukemia
• Myeloid rapid progression, affects the myeloid
  cells (red blood cells, granulocytes, and
  platelets)
• 84 from leukemia, 62 from leukemia excluding CLL,
  40 from myeloid leukemia
• Excess Relative Risk, respectively 4.1 Sv-1,
  7.7Sv-1, and 12.3 Sv-1

(Little 2007)
25
Findings Case Studies at SRS

• General Issue
• No analysis accounting tritium separately
• Difficult to infer much about tritium risks from
  studies

(Little 2007)
26
Findings Case Study at Chapelcross

• Chapelcross
• Town of Annan, southwest Scotland
• Purpose was to produce plutonium and tritium for
  UK nuclear weapons program and electricity for
  grid

http//en.wikipedia.org/wiki/FileChapelcross_Nucl
ear_Power_Station_2.jpg
(Little 2007)
27
Findings Case Study at Chapelcross

• McGeoghegan and Binks (2001)
• Study
• 2,628 workers assessed, 1955-1995
• Tritium doses not available
• Findings
• Mortality below that expected for non-tritium
  exposed for Scotland, England, and Wales
• Standardized Mortality Ratio (SMR) lt1
• Prostate cancer the only statistically
  significant positive trend of cancer mortality, 8
  deaths
• When lag increased, statistical significance
  eliminated
• Statistical significance for bronchitis deaths, 6
  deaths
• Suggestive increasing trend for prostate cancer,
  based on 12 cases
• Cases not monitored for tritium
• All but 2 workers left prior to tritium
  production

(Little 2007)
28
Findings Case Study of Canadian Nuclear Workers

• Zablotska et al (2004)
• Study
• Mortality follow up of 45,468 Canadian nuclear
  workers, 1957-1994
• Mean dose exposure of 13.5 mSv/ year, up to 19.7
  mSv / year
• Findings
• Mortality due to all cancers and leukemia
  excluding CLL less than national rates
• All cancers 531 observed deaths versus 721
  expected
• Leukemia excluding CLL 18 observed versus 22.6
  expected

(Little 2007)
29
Findings Case Study of Offspring of Canadian
Electric Power Workers

• Green et al (1997)
• Study
• Instances of congenital abnormalities for
  offspring of Canadian electric power workers
• Doses included, further analysis for parents with
  a recorded tritium dose 60 days before conception
  
• 763 case-control pairs of fathers, 165
  case-control pairs of mothers
• Abnormalities determined using Canadas
  congenital anomalies surveillance system
• Abnormalities detected within year 1
• Each child with an abnormality paired with a
  random child
• Ontario system (same year of birth, maternal age,
  marital status, and birthplace of each parent)

(Little 2007)
30
Findings Case Study of Offspring of Canadian
Electric Power Workers

• Findings
• Little risk for offspring abnormality when
  parents exposed to tritium

http//iopscience.iop.org/0952-4746/28/1/R01/pdf09
52-4746_28_1_R01.pdf
(Little 2007)
31
Expert Opinions State Toxicologist, Dr. Bill
Bress

• Tritium is a weak beta emitter
• - Can not penetrate the skin- Ingestion of
  tritiated water as main route of exposure- Most
  human cancers are linked to gamma emitters
• could not project a dose large enough at this
  site to be an acute human health risk.
• - Consumption of two liters of tritiated water
  per day, at a concentration of 20,000 pCi/L in
  order to cause cancer
• - 2.5 million pCi/L is the absolute maximum
  concentration of tritium
• - Tritium is water soluble
• Low potential for human ingestion of tritiated
  water - Contamination limited to surface and
  subsurface levels - No drinking water comes from
  the Connecticut River
• Minimal environmental health effects
• Levels of tritium in the monitoring wells are
  dropping and the leak has been stopped.

32
Expert OpinionsRadiological Health Chief, Dr.
Bill Irwin

• Possibility of greater risks
• Environmental effects not likely because of the
  dilution.
• Assumed that someone will drink from the
  Connecticut River
• Examples of tritium leaks from nuclear power
  plants taking place in New Jersey and Georgia.
• More preventative action
• - Aboveground pipes
• - Multiple barriers
• Routine monitoring and sampling

http//www.burlingtonfreepress.com/blog/secondopin
ion/uploaded_images/vermontyank-733499.jpg
33
Conclusions

• Case studies show that the number of cases of
  cancer linked with tritium were equal or less
  than those expected
• Offspring of those exposed to tritium showed no
  increased abnormalities over those offspring with
  parents not exposed to tritium
• The metabolism of tritium within the human body
  provides evidence for a minimal risk of cancer
• The location of Vermont Yankee on the
  Connecticut River has allowed for the dilution of
  tritiated water
• The radionuclide tritium does not exist in high
  enough concentrations at this site to cause
  negative human or environmental health effects.

34
Recommendations

• Continued monitoring of the soil and water
  surrounding Vermont Yankee to ensure levels of
  tritium continue to drop
• Consider the tritium leak as a potential
  indicator for the possibility of greater risks
  associated with Vermont Yankee.
• Increase the number of sampling sites in order
  to ensure high quality monitoring for not only
  tritium, but other harmful substances that might
  be leaking from the plant.

35
Updates on Yankee

• Vermont Yankee will be shut down as of 2012
  unless it is relicensed in 2011
• The Vermont House of Representatives has passed a
  bill requiring Vermont Yankee to set aside 20
  million dollars for the decommissioning

36
Summary
Goal To combine evidence of the health impacts
of tritium with case studies and current
knowledge pertaining to the Vermont Yankee
controversy in order to provide a risk assessment
of the Vermont Yankee tritium leak to human and
environmental health. Objectives Use
information from - Case studies with the
situation at Vermont Yankee - Lab studies on the
health effects of tritium on human analogs -
Biological pathways of tritium in the human
body - Mechanisms of tritium in plants.-
Interviews with State Toxicologist Bill Bress,
Radiological Health Chief Bill Irwin Conclusions
- The location of Vermont Yankee on the
Connecticut River has allowed for the dilution of
tritiated water - The radionuclide tritium does
not exist in high enough concentrations at this
site to cause negative human or environmental
health effects. Recommendations - Continued
monitoring - Consider the tritium leak as a
potential indicator - Increase the number of
sampling sites
37
Works Cited
Boyer, C. Vinchot, L. Fromm, M. Losset, Y.
Tatin-Froux, F. Guetat, P. Badot, P. M. Nov
2009. Tritium in Plants A Review of Current
Knowledge. Environmental and Experimental Botany,
67, (1), 34-51. Bress, Dr. Bill (19 March 2010).
State Toxicologist, Vermont Department of Health.
Interview Irwin, William (19 March 2010).
Radiological Health Chief, Vermont Department of
Health. Interview Le Guen, Bernard. 2009.
"Impact of tritium around EDF nuclear power
plants." Journal of Radiological Protection. 29
163-173. Little, M. P. Sep 2007. Systematic
review of epidemiological studies of exposure to
tritium. Journal of Radiological Projection, 28,
9-32. Takeda, et al. 2001. "Comparative
biokinetics of tritium in rats during continuous
ingestion of tritiated water and tritium-labeled
food." International Journal of Radiation Biology
77.3 375-381.Vermont Department of Health.
(2010). Investigation into tritium contamination
at vermont yankee nuclear power station.
Retrieved from healthvermont.gov/enviro/rad/yankee
/tritium.aspx Yamamoto, O., Seyama, T., Iton,
H., Fujimoto, N. 1998. Oral administration of
tritiated water (hto) in mouse. iii low
dose-rate irradiation and threshold dose-rate for
radiation risk. International Journal of
Radiation Biology, 73(5), 535-541.