Are My Health Problems Caused
by Radiation from Hanford?
Many people exposed to the radioactive releases from Hanford want to know if this exposure caused their health problems. Some people who were exposed have developed cancers and other diseases.
Many scientists agree that radiation exposure can increase the likelihood of certain health problems. However, at this time it is not scientifically possible to determine whether or not an individual's health problems were caused by radiation from Hanford.
Why the "Cause" Is Hard To Know
There are several reasons why it is hard to know if Hanford's releases were the cause of a person's health problems. One reason is that a number of factors may be involved in producing a disease. Another reason is that there are no tests or measurements that show past exposures to radiation.
A third reason is that a given radiation exposure may or may not result in harm to the body. 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.
Another Way To Look at the Question of What Caused Health Problems
Medical scientists respond to this question in terms of risk. Risk is the likelihood of getting a disease. Many scientists and public health officials believe that any radiation dose could increase the risk for cancer and possibly other health problems. (Dose is the amount of radiation absorbed by a part of the body.) 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.
To find out about the risk of disease from past radiation exposure, scientists do two kinds of studies. A dose reconstruction study attempts to reconstruct the levels of radiation dose that people may have received. This includes finding out what kinds of and how much radiation people were exposed to and how they were exposed, then estimating radiation dose levels. The second kind of study is a health study, or epidemiologic study. This study tells how much risk of disease is likely at a certain level of radiation dose.
Hanford Doses and Risk
Two studies focus on radiation doses from Hanford and the risk of health effects.
The Hanford Environmental Dose Reconstruction (HEDR) Project sought to find out the amount and types of radioactive materials Hanford released between 1944 and 1972, and how people were exposed. HEDR also provided estimates of the range of radiation doses people may have received. The HEDR Project found that Hanford released more than 200 kinds of radioactive elements (radionuclides). The study concluded that a radioactive form of iodine, iodine-131, accounted for more than 98 percent of the radiation dose that most people received outside the Hanford site.
Additional scientific work for this study is being conducted by the Centers for Disease Control and Prevention (CDC). The HEDR Task Completion Working Group oversees this work. The Working Group includes representatives of the state health departments of Idaho, Oregon and Washington, and CDC. The additional HEDR work focuses on
(1) exposures to people who were on the Hanford site, and (2) exposures from Hanford's releases to the Columbia River. Reports are expected in 2000 and 2001, respectively.
The Hanford Thyroid Disease Study (HTDS) is a health study. Its purpose is to investigate whether thyroid disease is related to levels of estimated radiation dose among persons exposed 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.
