HANFORD DOWNWINDERS INFORMATION SITE

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Hanford's Radioactive Releases

How Radiation Exposure Occurs

What the Body Does with Radioactivity

Hanford's Releases and Radiation Dose

Air Releases chart

River Releases chart

Selected Sources

Production of plutonium at the Hanford Site released many radioactive substances into the environment for more than 40 years. This publication discusses the way that exposure to radiation occurs, how the body handles internal radiation exposure, and which tissues and organs received most of the dose from the radioactive materials released from Hanford. Dose is the amount of radiation, or energy, absorbed by the body.

HANFORD'S RADIOACTIVE RELEASES

In producing plutonium, Hanford released radioactive materials into the air and the Columbia River. Much of the information about the radiation released from Hanford comes from the Hanford Environmental Dose Reconstruction (HEDR) Project. The HEDR Project estimated how much radioactive material was released from Hanford, how that material may have reached and exposed people, and what radiation dose the people living in the HEDR study area may have received from Hanford's releases.

Scientific experts for lawsuits against Hanford contractors have estimated that Hanford's releases were higher than the HEDR scientists estimated them to be. The Centers for Disease Control and Prevention (CDC) is now evaluating these reports.

When using information from dose reconstruction studies, readers should keep in mind that the strength of a study's findings is affected by a number of factors, such as the quality of the information available about doses and the study's design.

The HEDR Project estimated that six radioactive materials released into the air account for nearly all the radiation dose a person may have received from the air pathway. The Project also estimated that five substances account for most of the dose a person may have received from the water pathway. (The air and water pathways are the key ways in which people received radiation exposure.) These 11 substances are listed in the tables later in this publication. The HEDR Project also calculated dose estimates for representative (typical) individuals. The Project's Technical Steering Panel published the summary results and representative dose estimates in April 1994.

HOW RADIATION EXPOSURE OCCURS

Radiation exposure can be external or internal. External radiation exposure occurs when the radiation source is outside, or external, to the body. Examples of this kind of exposure are standing in a cloud of radioactive gas or swimming in water that has radioactive material in it. Internal radiation exposure occurs when radioactive material is taken into the body by eating, drinking, breathing, or through breaks in the skin.

In addition to the exposure to Hanford radiation, external and internal radiation exposure comes from a variety of sources. These include medical uses of radiation, such as medical and dental X-rays, and radioactive substances in the environment, such as radon and cosmic rays. Most U.S. residents have also been exposed to fallout from nuclear weapons tests, such as the Nevada Test Site in the 1950s and 1960s.

For most people exposed to Hanford's radioactive releases outside Hanford's boundaries, internal radiation exposure is estimated to be the main exposure route. This information sheet focuses on internal exposure from radioactive materials released by Hanford.

The HEDR Project estimated that iodine-131 accounts for 98 percent of the radiation dose that most people received from Hanford's air releases. Most of this dose came from drinking milk from cows and goats that fed on pasture downwind of Hanford, and from eating locally grown leafy vegetables and fruit. The HEDR Project also concluded that people were exposed by Hanford's radioactive releases to the Columbia River, mainly through eating non-migratory fish. People also were exposed by drinking Columbia River water, spending time along the shoreline or swimming in contaminated stretches of the river.

WHAT THE BODY DOES WITH RADIOACTIVITY

When radiation enters the body and hits a cell, one of four things can happen:
1. Radiation may pass through the cell without doing damage.
2. It may damage the cell, but the cell may be able to repair the damage before producing new cells.
3. It may damage the cell in such a way that the damage is passed on when new cells are formed.
4. Or it may kill the cell.

If radiation passes through the cell or the cell repairs the damage (1 or 2 above), there is no lasting damage or health effect. If the damage is passed on when new cells form (3 above), there may be a delayed health effect such as cancer. If radiation kills a cell (4 above), there will be immediate health effects if the dose is high and many cells die. From what is currently known, doses to people outside Hanford's boundaries from Hanford's releases were not high enough to produce immediate or direct effects.

To understand how the body handles radioactivity from internal exposure, it is also important to know where the radioactivity goes in the body and how long it remains.

Distribution in the Body

Some radioactive substances concentrate in specific organs. Others are distributed throughout the body. Some substances that concentrate in one organ may also give a radiation dose to other organs and tissues.

When a radioactive substance concentrates primarily in one organ of the body, that organ receives a larger radiation dose from the substance than do other organs or tissues. This is called an organ dose. Some of the radioactive substances that concentrate in specific organs are chemically similar to substances the body needs in order to function. The body does not recognize the difference between a radioactive and nonradioactive substance. For example, strontium-90 is chemically similar to calcium. So the body uses strontium in the bone in much the same way it does calcium.

Other radioactive substances may concentrate in certain organs or tissues even though they are not chemically similar to substances the body needs to function. An example is neptunium-239, which concentrates in the gastrointestinal tract.

Instead of concentrating in one organ, some radioactive substances are distributed throughout the body. This is called a whole-body dose. Tritium, for example, is a form of hydrogen. Since hydrogen is part of water molecules, which are present throughout the body, tritium is distributed throughout the body and delivers a dose to all tissues.

Some of the radioactive substances that concentrate in one organ or tissue are also distributed and absorbed by other organs and tissues. In this case, the substance will give a radiation dose to those other organs or tissues, but that dose typically will be much smaller. For example, iodine-131 concentrates in the thyroid gland. The parathyroid glands, which lie close to the thyroid, also receive a dose from iodine-131. However, the radiation dose to the normal parathyroid is from four to 20 times lower than the dose the thyroid gland receives. In addition, iodine-131 gives a radiation dose to other organs and tissues, such as the reproductive organs and breast tissue. However, the dose from iodine-131 received by the reproductive organs and breast tissue is much less than the dose to the thyroid. For example, the radiation dose to the breast is 30,000 times less than the dose to the thyroid. The radiation dose to the ovary is nearly one million times less than the dose to the thyroid.

Length of Time in the Body

Once a radioactive substance is taken into the body, it will continue to give off radiation until either the radioactivity has decayed or the body has eliminated the substance through normal metabolism. Both of these processes occur at the same time.

The rate of radioactive decay of a substance determines its half-life. The half-life is the amount of time it takes for a radioactive substance to lose one-half of its radioactivity. Half-lives for different substances vary from millionths of a second to billions of years. When an atom decays and becomes stable, it is no longer radioactive.

RADIATION AND HEALTH

Much of what is known about radiation and human health comes from studies of people exposed to medical uses of radiation, survivors of the atomic bombing of Japan, and, more recently, people exposed to radiation from the accident at the Chernobyl plant. People exposed in these situations generally received higher radiation doses than did people exposed to radiation released from Hanford. In general, people exposed by Hanford's releases received lower radiation doses over longer periods of time.

Potential Health Effects

Radiation can cause many types of cancer. Whether or not exposure to radiation will cause cancer depends on a variety of factors. These include: the amount and type of radiation dose, individual characteristics that make some people more susceptible than others, the person's age and gender, whether the exposure occurred over a short or a long time, and the presence of other substances that enhance the cancer-causing power of radiation. Scientists do not yet agree on the extent to which low-dose radiation, such as people received from Hanford, causes cancer.

HHIN has heard from many Hanford-exposed people who express concern that other non-cancer health problems, such as autoimmune thyroid disease or multiple sclerosis, may be related to exposure to radiation from Hanford. Very little is known from human health studies about low-dose radiation and health problems other than cancer. A limited number of studies have investigated this relationship. Current studies and future studies may provide more information. It is also possible that current research methods may not be sensitive enough to detect a link between low-dose radiation and such health problems, if a link exists.

Many scientists and public health officials believe that any radiation dose could increase the risk for cancer and possibly other health problems. Having an increased risk does not always lead to developing a disease. Having an increased risk means that the chances of getting a disease are higher than if the exposure had not occurred.

Current Studies of Low-Dose Health Effects BEIR VII. In 1999 the National Research Council began a study to review the last 10 years of studies on the health effects of low-dose ra-diation. Over the next three years, this study (called BEIR VII) will develop principles for determining the amount of risk from low-dose exposures.

Hanford Thyroid Disease Study (HTDS). The purpose of the HTDS is to investigate whether thyroid disease is related to levels of estimated radiation dose among persons ex-posed as children to Hanford's air releases of iodine-131 during the 1940s and 1950s. The Fred Hutchinson Cancer Research Center conducted the research. CDC sponsors the study.

The draft study report, made public in January 1999, does not find a link between estimated thyroid dose from iodine-131 and the amount of thyroid disease in the study population. The study did find thyroid diseases among HTDS participants. However, those who had higher estimated radiation doses appeared to be no more likely to have thyroid diseases than were those who had lower doses. CDC notes that these results do not prove that such a link does not exist. It is not possible for an epidemiologic study such as the HTDS to determine if an individual person's thyroid disease is or is not caused by exposure to radiation released from Hanford.

In February 1999, CDC asked the National Academy of Sciences (NAS) to conduct a scientific peer review of the HTDS Draft Final Report. The NAS completed its peer review in December 1999. The review panel wrote that the HTDS investigators "probably overstated the strength of their findings that there was no radiation effect." The panel found that the study methods were of high quality. However, the panel said that additional analyses are needed to explain what the study data mean about the full range of possible risk to the thyroid. The panel commended CDC for public involvement during the nine years of the study but found shortcomings in the way the report was released. The panel recommended several steps for improving communication of the final report to the public.

CDC plans to respond to issues raised by the NAS, by other scientific reviewers and by the public in a revised final HTDS report. This report is expected by December 2000.

HANFORD'S RELEASES AND ORGANS THAT MAY BE AFFECTED

Based on the HEDR Project's representative dose estimates, it is likely that Hanford's releases resulted in low whole-body doses. A whole-body dose is one in which approxi-mately the same dose is received by each organ, as may happen with exposure to tritium. But some people - particularly those living near Hanford before 1960 - may have received high doses to the thyroid gland or other organs.

The tables below provide information on the six radioactive materials Hanford released to the air and the five released to the Columbia River that contributed the most to radiation dose, as estimated by the HEDR Project. In the first two columns, the tables list these radioactive substances and show HEDR's estimates (measured in curies) of how much Hanford released. For each substance, the table also shows the main exposure pathway, the main body organs or tissues affected and the half-life of the substance.

Radioactive substances released to the air for which doses are being estimated by the Dose Reconstruction Project.
Substance Amount Released
from Hanford		 Main Routes
of Exposure		 Organs Receiving
Main Dose		 Half-life
Iodine-131 762,000 curies* ingestion thyroid 8 days
Ruthenium-103 1,160 curies external
inhalation		 whole body
lungs		 39.4 days
Ruthenium-106 388 curies inhalation
ingestion		 lungs
GI tract		 368 days
Strontium-90 64.3 curies ingestion bone surfaces
red bone marrow		 28.8 years
Plutonium-239 1.78 curies inhalation lungs
bone surfaces		 24,100 years
Cerium-144 3,770 curies inhalation
ingestion		 lungs
GI tract		 284 days

*For comparison: The Three Mile island nuclear power plant accident in 1979 released between 16 and 24 curies of iodine-131. The 1986 accident at the Chernobyl plant released between 35 million and 49 million curies of iodine-131. The nuclear bomb fallout from aboveground tests at the Nevada test Site (1951-1970) released approximately 150 million curies of iodine-131.

Note: Scientific experts for lawsuits against Hanford contractors have estimated that Hanford's iodine 131 releases were higher (900,000 curies) than the HEDR estimate shown above.

Radioactive substances released to the Columbia River for which doses are being estimated by the Dose Reconstruction Project.
Substance Amount Released from Hanford (as estimated by the HEDR Project)* Main Routes
of Exposure		 Organs Receiving
Main Dose		 Half-life
Phosphorus-32 229,000 curies ingestion red bone marrow 14.3 days
Zinc-65 491,000 curies ingestion whole body 245 days
Arsenic-76 2,520,000 curies ingestion GI tract
stomach for infants		 26.3 hours
Sodium-24 12,600,000 curies ingestion stomach 15 hours
Neptunium-239 6,310,000 curies ingestion GI tract 2.4 days

*From a 1994 HEDR Project report (Heeb, PNWD-2223 HEDR, January 1994).

FOR MORE INFORMATION

This information sheet serves as an introduction to the topic of how certain radioactive substances released from hanford are handled by the body. Other network publications can provide further information:

The Release of Radioactive Materials from Hanford: 1944-1972 provides more detailed information about Hanford's radioactive releases.

An Overview of Hanford and Radiation Health Effects offers a brief history of Hanford's releases and information on the potential health effects of radiation.

Potential Health Problems from Exposure to Selected Radionuclides: Plutonium, Strontium, Cerium and Ruthenium discusses four radionuclides Hanford released to the air.

Radionuclides in the Columbia River: Possible Health Problems in Humans and Effects on Fish discusses five radio-nuclides Hanford released to the river.

Selected Sources:

Heeb, C. M. Radionuclide Releases to the Atmosphere from Hanford Operations, 1944-1972. PNWD-2222 HEDR, January 1994.

Heeb, C. M. and D. J. Bates. Radionuclide Releases to the Columbia River from Hanford Operations, 1944-1971. PNWD-2223 HEDR, January 1994.

Phipps, A.W., G.W. Kendall, J.W. Stather, and T.P. Fell. Committed Equivalent Organ Doses and Committed Effective Doses from Intakes of Radionuclides. National Radiological Protection Board of the United Kingdom, NPRB-R245, 1991.

Roessler, Genevieve. "Radiation Dose," Radiation Dose Newsletter by the Technical Steering Panel of the Hanford Environmental Dose Reconstruction Project. Oct. 1993.

Till, John and H. Robert Meyers, ed. Radiological Assessment: A Textbook on Environmental Dose Analysis. Washington, D.C.: U.S. Government Printing Office, 1983.

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