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

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

Background InformationBackground 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_Sunset/Ball%20HydroCarbon%20Chrono/IMG_7753.jpg

Understanding UnitsUnderstanding 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

Tritium and Vermont Yankee: Tritium and Vermont Yankee: Department of Health TimelineDepartment 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)

(Vermont Department Health 2010)

GZ-1: <LLD GZ-2: <LLD GZ-3: 52,000 GZ-4: 2,400 GZ-5: <LLD GZ-6: <LLD GZ-7: 757,000GZ-8: No sample; dry well GZ-9: <LLD GZ-10: <LLD GZ-11: 750 GZ-12: 267,000 GZ-13S: <LLD GZ-13D: 1,200 GZ-14S: 258,000 GZ-14D: <LLD GZ-15: 710,000 GZ-16: <LLD GZ-17: <LLD GZ-18: no well yet GZ-19S: <LLD GZ-19D: <LLD GZ-20: 130,000 GZ-21: 2.028 million

Most recent well results in (pCi/l) or below the lower level of detection (<LLD).

GoalGoal

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.

ObjectivesObjectives• 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

Tritium SourcesTritium Sources

• Natural tritium is created at a rate of 0.15-Natural tritium is created at a rate of 0.15-0.2 kg/yr0.2 kg/yr

• Nuclear sources contribute 0.06 kg/yrNuclear sources contribute 0.06 kg/yr

• Atmospheric weapon tests totaled 560 kg Atmospheric weapon tests totaled 560 kg by 1963 but by 2008 were reduced to by 1963 but by 2008 were reduced to about 40 kgabout 40 kg

(Boyer 2009)

The Tritium CycleThe Tritium Cycle

• Tritium is most commonly Tritium is most commonly found as tritiated water, found as tritiated water, tritiated methane and tritiated tritiated methane and tritiated molecular hydrogen. molecular hydrogen.

• Tritiated water moves Tritiated water moves through the water cycle as through the water cycle as normal water does, moving normal water does, moving through water bodies, through water bodies, atmosphere, soils, atmosphere, soils, groundwater, largely ending groundwater, largely ending up in oceans. up in oceans.

http://dnr.wi.gov/org/caer/ce/eek/earth/groundwater/images/groundwater.gif

Findings: Tritium in PlantsFindings: Tritium in PlantsPlant 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)

• Differences in plant Differences in plant absorption of Tritiumabsorption of Tritium• C3 plants absorb more C3 plants absorb more

atmospheric tritium during the atmospheric tritium during the day than at nightday than at night

• C4 plants typically contain C4 plants typically contain less tritium than C3 plantsless tritium than C3 plants

• Lichen, mosses and fungi Lichen, mosses and fungi absorb tritiated water rapidly absorb tritiated water rapidly because they lack a cuticle because they lack a cuticle and stomatal apparatusand stomatal apparatus

Findings: Tritium in PlantsFindings: Tritium in Plants

(Boyer 2009)

http://img.sparknotes.com/figures/B/b1ab5bb87aee74a86fdae78ed564e663/stoma.gif

• Boyer’s ConclusionsBoyer’s Conclusions

• It is assumed that high levels of tritium It is assumed that high levels of tritium exposure will cause DNA mutations but the exposure will cause DNA mutations but the environmental impacts are minimized by environmental impacts are minimized by extremely limited exposure. extremely limited exposure.

• Based on Boyer’s findings the environmental Based on Boyer’s findings the environmental health impacts of the Vermont Yankee tritium health impacts of the Vermont Yankee tritium leaks will not be significant. leaks will not be significant.

Findings: Tritium in PlantsFindings: Tritium in Plants

(Boyer 2009)

Findings: Studies on Rats and MiceFindings: 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

(Vermont Department Health, 2010)

GZ-1: <LLD GZ-2: <LLD GZ-3: 52,000 GZ-4: 2,400 GZ-5: <LLD GZ-6: <LLD GZ-7: 757,000GZ-8: No sample; dry well GZ-9: <LLD GZ-10: <LLD GZ-11: 750 GZ-12: 267,000 GZ-13S: <LLD GZ-13D: 1,200 GZ-14S: 258,000 GZ-14D: <LLD GZ-15: 710,000 GZ-16: <LLD GZ-17: <LLD GZ-18: no well yet GZ-19S: <LLD GZ-19D: <LLD GZ-20: 130,000 GZ-21: 2.028 million

Most recent well results in (pCi/l) or below the lower level of detection (<LLD).

Findings: Studies on Rats and MiceFindings: Studies on Rats and Mice

• 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.

Study by Takeda (2001):

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

• Chemical half life = 12.35 yearsChemical half life = 12.35 years• Biological half life: Biological half life:

• 10 days for HTO (90% of uptake)10 days for HTO (90% of uptake)• 30 days for OBT (10% of uptake)30 days for OBT (10% of uptake)• 450 days for trace amounts450 days for trace amounts

• Pathways: inhalation, ingestion, absorption Pathways: inhalation, ingestion, absorption through dermisthrough dermis• Rate of absorption depends on chemical formRate of absorption depends on chemical form• HTO transferred fastestHTO transferred fastest

• Radiation penetrates 6 Radiation penetrates 6 m, but human m, but human epidermis is 20-100 epidermis is 20-100 m thickm thick

Findings: Findings: Tritium in the Human BodyTritium in the Human Body

Tritium in the Human BodyTritium in the Human Body

• Travels through same biokinetic pathways as Travels through same biokinetic pathways as water/organic compoundswater/organic compounds• Uniform distribution as HTO Uniform distribution as HTO • Uneven distribution as OBT: stored in adipose tissue Uneven distribution as OBT: stored in adipose tissue

and tissue with high multiplication rateand tissue with high multiplication rate

• Replaces hydrogen in all compoundsReplaces hydrogen in all compounds• Same physical, chemical, pharmacological propertiesSame physical, chemical, pharmacological properties

• 99% excreted as HTO and OBT99% excreted as HTO and OBT

• Effective dose of OBT is 2.3 times higher than Effective dose of OBT is 2.3 times higher than that of HTOthat of HTO• Accounts for risk of incorporation into DNA (impacts Accounts for risk of incorporation into DNA (impacts

unknown)unknown)

• Difficulty of dose measurementDifficulty of dose measurement• Low number of contamination casesLow number of contamination cases• Not highly radioactiveNot highly radioactive• To have potential impacts, exposure must be To have potential impacts, exposure must be

1000 times the levels found in nature1000 times the levels found in nature

Tritium in the Human BodyTritium in the Human Body

Tritium in the Human BodyTritium in the Human Body• Effects on human body similar to those observed Effects on human body similar to those observed

in plantsin plants• Once absorbed, it quickly passes throughOnce absorbed, it quickly passes through• Assumptions:Assumptions:

• DNA mutationsDNA mutations• Cell damageCell damage

• Damage caused from radiation, not from Damage caused from radiation, not from molecule itself!molecule itself!

• Unlikely that humans will be exposed to high Unlikely that humans will be exposed to high enough concentrations at Vermont Yankeeenough concentrations at Vermont Yankee

} Exposure to high doses

StudiesStudies

• Long term effects unknownLong term effects unknown• Exposed lymphocytes and marrow cells to HTO Exposed lymphocytes and marrow cells to HTO

showed:showed:• Does not increase RBEDoes not increase RBE• Chromosomal aberrations increased but Chromosomal aberrations increased but

sister- chromatid exchanges did notsister- chromatid exchanges did not• No conclusions about uptake via fruits and No conclusions about uptake via fruits and

vegetables should be madevegetables should be made

(Tanaka 1994), (Boyer 2009)

• Dose levels account for Dose levels account for people living close to sitepeople living close to site• Adults eating fish within a Adults eating fish within a

500 m radius500 m radius• Sunbathing (100 h/yr)Sunbathing (100 h/yr)• Swimming (20 h/yr)Swimming (20 h/yr)

• Increased risk for certain Increased risk for certain groups (ex. fisherman)groups (ex. fisherman)

• Risk of exposure Risk of exposure extremely lowextremely low

Impacts of Controlled ReleasesImpacts of Controlled ReleasesFlamanville, Manche, France

http://www.world-nuclear-news.org/uploadedImages/wnn/Images/

Flamanville%203.jpg

(Le Guen 2009)

Findings: Case Studies at Findings: Case Studies at Savannah River Site (SRS)Savannah River Site (SRS)

• Savannah River Savannah River Site Site

• South Carolina South Carolina

• Not in operation todayNot in operation today

• Clean up of past Clean up of past nuclear weapons nuclear weapons manufacturing manufacturing

http://en.wikipedia.org/wiki/File:SavannahRiverSite_ISS012-E-

16633.jpg

(Little 2007)

Findings: Case Studies at SRSFindings: Case Studies at SRS Cragle Cragle et al et al (1998)(1998)• StudyStudy

– Mortality of 9,860 white male workers at the SRS, 1952 to 1980Mortality of 9,860 white male workers at the SRS, 1952 to 1980– Little data on actual tritium doses Little data on actual tritium doses – Estimated doses:Estimated doses:

• 800 employees received > 0.5 mSv per year800 employees received > 0.5 mSv per year• 1 employee > 30 mSv per year 1 employee > 30 mSv per year

• FindingsFindings– Few indications of excess mortalityFew indications of excess mortality– 18 prostate cancer deaths versus 21.15 expected deaths18 prostate cancer deaths versus 21.15 expected deaths– Marginally increasing trend for leukemia at 25 deaths versus Marginally increasing trend for leukemia at 25 deaths versus

19.63 expected deaths19.63 expected deaths– Further analysis Further analysis

(Little 2007)

Findings: Case Studies at SRSFindings: Case Studies at SRS Richardson and Wing (2007)Richardson and Wing (2007)• StudyStudy

• Association between radiation exposure and leukemia, 1950-2002Association between radiation exposure and leukemia, 1950-2002• Doses of tritium, photons, and neutrons were estimatedDoses of tritium, photons, and neutrons were estimated

• FindingsFindings– Results into 3 different groups:Results into 3 different groups:

• LeukemiaLeukemia

• Leukemia excluding chronic lymphocytic leukemia (most common Leukemia excluding chronic lymphocytic leukemia (most common type)type)

• CLL: slow progression, affects lymphoid cells (white blood cells) CLL: slow progression, affects lymphoid cells (white blood cells) • Myeloid leukemia Myeloid leukemia

• Myeloid: rapid progression, affects the myeloid cells (red blood Myeloid: rapid progression, affects the myeloid cells (red blood cells, granulocytes, and platelets)cells, granulocytes, and platelets)

• 84 from leukemia, 62 from leukemia excluding CLL, 40 from myeloid 84 from leukemia, 62 from leukemia excluding CLL, 40 from myeloid leukemialeukemia

– Excess Relative Risk, respectively: 4.1 SvExcess Relative Risk, respectively: 4.1 Sv-1-1, 7.7Sv, 7.7Sv-1-1, and 12.3 Sv, and 12.3 Sv-1-1

(Little 2007)

Findings: Case Studies at SRSFindings: Case Studies at SRS

• General IssueGeneral Issue

– No analysis accounting tritium separatelyNo analysis accounting tritium separately

– Difficult to infer much about tritium risks from Difficult to infer much about tritium risks from studies studies

(Little 2007)

Findings: Case Study at ChapelcrossFindings: Case Study at Chapelcross

• ChapelcrossChapelcross

– Town of Annan, Town of Annan, southwest Scotlandsouthwest Scotland

– Purpose was to Purpose was to produce plutonium produce plutonium and tritium for UK and tritium for UK nuclear weapons nuclear weapons program and program and electricity for grid electricity for grid

http://en.wikipedia.org/wiki/File:Chapelcross_Nuclear_Power_Station_2.jpg

(Little 2007)

Findings: Case Study at ChapelcrossFindings: Case Study at ChapelcrossMcGeoghegan and Binks (2001)McGeoghegan and Binks (2001)• StudyStudy

• 2,628 workers assessed, 1955-19952,628 workers assessed, 1955-1995

• Tritium doses not available Tritium doses not available

• FindingsFindings• Mortality below that expected for non-tritium exposed for Scotland, England, and Mortality below that expected for non-tritium exposed for Scotland, England, and

WalesWales

• Standardized Mortality Ratio (SMR) <1 Standardized Mortality Ratio (SMR) <1

• Prostate cancer the only statistically significant positive trend of cancer mortality, 8 Prostate cancer the only statistically significant positive trend of cancer mortality, 8 deaths deaths

• When lag increased, statistical significance eliminatedWhen lag increased, statistical significance eliminated

• Statistical significance for bronchitis deaths, 6 deaths Statistical significance for bronchitis deaths, 6 deaths

• Suggestive increasing trend for prostate cancer, based on 12 casesSuggestive increasing trend for prostate cancer, based on 12 cases

• Cases not monitored for tritiumCases not monitored for tritium

• All but 2 workers left prior to tritium production All but 2 workers left prior to tritium production

– (Little 2007)

Findings: Case Study of Findings: Case Study of Canadian Nuclear WorkersCanadian Nuclear Workers

Zablotska Zablotska et al et al (2004) (2004)

• StudyStudy

• Mortality follow up of 45,468 Canadian nuclear workers, 1957-Mortality follow up of 45,468 Canadian nuclear workers, 1957-19941994

• Mean dose exposure of 13.5 mSv/ year, up to 19.7 mSv / yearMean dose exposure of 13.5 mSv/ year, up to 19.7 mSv / year

• FindingsFindings

• Mortality due to all cancers and leukemia excluding CLL less Mortality due to all cancers and leukemia excluding CLL less than national ratesthan national rates

• All cancers: 531 observed deaths versus 721 expected All cancers: 531 observed deaths versus 721 expected

• Leukemia excluding CLL: 18 observed versus 22.6 expected Leukemia excluding CLL: 18 observed versus 22.6 expected (Little 2007)

Findings: Case Study of Offspring of Findings: Case Study of Offspring of Canadian Electric Power WorkersCanadian Electric Power Workers

Green Green et alet al (1997) (1997)• StudyStudy

• Instances of congenital abnormalities for offspring of Canadian Instances of congenital abnormalities for offspring of Canadian electric power workerselectric power workers

• Doses included, further analysis for parents with a recorded Doses included, further analysis for parents with a recorded tritium dose 60 days before conception tritium dose 60 days before conception

• 763 case-control pairs of fathers, 165 case-control pairs of 763 case-control pairs of fathers, 165 case-control pairs of mothersmothers

• Abnormalities determined using Canada’s congenital anomalies Abnormalities determined using Canada’s congenital anomalies surveillance system surveillance system

• Abnormalities detected within year 1Abnormalities detected within year 1• Each child with an abnormality paired with a random childEach child with an abnormality paired with a random child

• Ontario system (same year of birth, maternal age, marital Ontario system (same year of birth, maternal age, marital status, and birthplace of each parent)status, and birthplace of each parent)

(Little 2007)

Findings: Case Study of Offspring of Findings: Case Study of Offspring of Canadian Electric Power WorkersCanadian Electric Power Workers

• FindingsFindings• Little risk for offspring abnormality when parents exposed to Little risk for offspring abnormality when parents exposed to

tritium tritium

http://iopscience.iop.org/0952-4746/28/1/R01/pdf0952-4746_28_1_R01.pdf

(Little 2007)

Expert Opinions: 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.

Expert Opinions:Radiological 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/secondopinion/uploaded_images/vermontyank-733499.jpg

ConclusionsConclusions• Case studies show that the number of cases of cancer linked with tritium were Case studies show that the number of cases of cancer linked with tritium were equal or less than those expectedequal or less than those expected

• Offspring of those exposed to tritium showed no increased abnormalities over Offspring of those exposed to tritium showed no increased abnormalities over those offspring with parents not exposed to tritiumthose offspring with parents not exposed to tritium

• The metabolism of tritium within the human body provides evidence for a The metabolism of tritium within the human body provides evidence for a minimal risk of cancerminimal risk of cancer

• The location of Vermont Yankee on the Connecticut River has allowed for the The location of Vermont Yankee on the Connecticut River has allowed for the dilution of tritiated water dilution of tritiated water

• The radionuclide tritium does not exist in high enough concentrations at this The radionuclide tritium does not exist in high enough concentrations at this site to cause negative human or environmental health effects. site to cause negative human or environmental health effects.

RecommendationsRecommendations• Continued monitoring of the soil and water surrounding Vermont Yankee Continued monitoring of the soil and water surrounding Vermont Yankee to ensure levels of tritium continue to drop to ensure levels of tritium continue to drop

• Consider the tritium leak as a potential indicator for the possibility of tritium leak as a potential indicator for the possibility of greater risks associated with Vermont Yankee.greater risks associated with Vermont Yankee.

• Increase the number of sampling sites in order to ensure high quality Increase the number of sampling sites in order to ensure high quality monitoring for not only tritium, but other harmful substances that might be monitoring for not only tritium, but other harmful substances that might be leaking from the plant.leaking from the plant.

Updates on YankeeUpdates on Yankee

• Vermont Yankee will be shut down as of Vermont Yankee will be shut down as of 2012 unless it is relicensed in 20112012 unless it is relicensed in 2011

• The Vermont House of Representatives The Vermont House of Representatives has passed a bill requiring Vermont has passed a bill requiring Vermont Yankee to set aside 20 million dollars for Yankee to set aside 20 million dollars for the decommissioningthe decommissioning

SummarySummaryGoal: 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.

ObjectivesUse 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 - The location of Vermont Yankee on the Connecticut River has allowed for the dilution of tritiated water water - The radionuclide tritium does not exist in high enough concentrations at this site to cause - The radionuclide tritium does not exist in high enough concentrations at this site to cause negative human or environmental health effects. negative human or environmental health effects.

RecommendationsRecommendations - Continued monitoring- Continued monitoring- Consider the tritium leak as a potential indicatortritium leak as a potential indicator- Increase the number of sampling sites- Increase the number of sampling sites

Works CitedWorks CitedBoyer, 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.