Examples of diseases of the nervous system include multiple sclerosis, myasthenia gravis, Parkinson's disease, amyotrophic lateral sclerosis (ALS � also known as Lou Gehrig's disease), Alzheimer's disease and brain tumors. Birth defects of the nervous system include neural tube defects, mental retardation and small brain size.

Researchers know more about how high-dose radiation affects the nervous system than about how low-dose radiation affects it. Researchers also know more about exposures from external sources than from radioactive substances acting within the body (internal exposure). Hanford's releases, however, resulted in low whole-body doses from mainly internal exposure, according to estimates of the Hanford Environmental Dose Reconstruction Project.¹ Nonetheless, to understand the range of potential health effects, it is useful to look at what is known about the health effects of high-dose radiation from external exposures.

High doses of radiation can be defined as greater than 50 rem to the whole body. High-dose radiation is used to treat cancer. In the past it was used to treat benign conditions such as ringworm of the scalp and enlargement of the thymus gland in the neck. Some Japanese atomic bomb survivors, nuclear industry workers and survivors of nuclear accidents also received high doses of radiation. Health effects in people exposed to high radiation doses include effects on the brain, spinal cord and peripheral nerves.

Effects on the Brain

People treated with radiation for brain tumors often receive doses of a few thousand rad to the head, usually over a period of days or weeks. Health effects that can occur within days or weeks of treatment include swelling of the brain, seizures, paralysis and confusion. Long-term effects that may occur include the destruction of brain cells, changes in the blood vessels of the brain, seizures and confusion.²

Other studies have also linked radiation exposure to the development of brain tumors.⁴ These were studies of people treated with radiation for conditions of the head and neck, arthritis of the spine and acute lymphocytic leukemia.

However, studies of Japanese atomic bomb survivors have not reported a link between high-dose radiation exposure and brain tumors.⁵ While these studies found no evidence of a radiation effect for brain tumors, there is evidence of an increased risk for other nervous system tumors in people exposed to the atomic bomb explosions before they were 20 years old.⁶ These atomic bomb studies have, however, found measurable nervous system effects on some children born to Japanese women who were pregnant during the bombings of Hiroshima and Nagasaki. The women received whole-body radiation doses ranging from 50 to 100 rad between eight and 25 weeks after conception. The children had an increased risk for small brain size and mental retardation, lower intelligence test scores and decreased school achievement.⁷

Effects on the Spinal Cord

The spinal cord is generally more sensitive to the acute (short-term) effects of radiation than is the brain. It also takes less time for radiation-induced damage to the spinal cord to show up than similar injury to the brain.

Myelitis is sometimes delayed, not occurring until four months to three years after radiation exposure. This delayed effect is due to scarring of the spinal cord and is not a direct effect on spinal cord nerve cells. When delayed, a person may experience more severe problems such as paralysis and lack of bladder control.⁸ Another delayed effect of high-dose radiation exposure to the spine is the development of spinal cord tumors years after the radiation exposure.⁹

Health effects in people exposed to high radiation doses include effects on the brain, spinal cord and peripheral nerves.

Effects on the Peripheral Nerves

Peripheral nerves (which connect the brain and spinal cord to other parts of the body) are among the parts of the body most resistant to radiation.¹⁰ Nonetheless, the Israeli children discussed above in the study by Ron and her colleagues had a higher rate of cancerous and benign tumors of peripheral nerves than people not exposed to radiation.¹¹

Birth Defects of the Nervous System in Children of Hanford Workers

Lowell Sever and others conducted a case-control study of children born in the Hanford area.¹² The researchers investigated if there was a link between a parent's work exposure to low-level external radiation and birth defects in that worker's children. The study investigated births between 1957 and 1980 since only a few hospital records were available for earlier years.

The researchers found that the higher the radiation dose received by parents before their children were born, the more likely the children were to be born with neural tube defects. Defects of the neural tube, which develops into the spinal cord and brain, occur when the tube fails to close completely during the early stages of pregnancy.

Researchers also reported a link between parental employment at Hanford and two non-neurologic birth defects: congenital dislocation of the hip and tracheoesophageal fistula, an abnormal connection between the trachea (the windpipe) and the esophagus (the part of the digestive tract that connects the mouth to the stomach). However, these two birth defects were not linked with parental exposure to radiation as not all Hanford workers were exposed to radiation at work. Many worked in offices and did not receive any occupational radiation exposure. This study did not include parents' exposure to radioactive materials outside of work, including environmental releases from Hanford, medical procedures or background radiation.

Birth Defects of the Nervous System in Communities near Hanford

Sever and others also conducted a study of the rate of birth defects in communities near the Hanford Site.¹³ The researchers investigated whether rates of birth defects among infants in the Hanford area were higher than expected potentially because of exposure to radioactivity from Hanford operations.

The study was conducted before any dose estimates were available from the Hanford Environmental Dose Reconstruction Project. Also, the study's dose estimate for the public includes only the years 1974 through 1980, during which there were limited Hanford operations and emissions.

Brain Tumors Among U.S. Nuclear Workers

Deaths from brain tumors are unusual in the general population (4.1 deaths per 100,000 people). In a work force of several thousand, even a small number of cases (two to five) points to a higher number of such deaths than would ordinarily be expected.

Victor Alexander reviewed studies of workers at 10 nuclear facilities.¹⁴ Radiation doses were available for workers at eight of the facilities. For three of the groups, doses

Determining the occurence of nervous system diseases can be difficult.

included both external and internal exposure. Cumulative average whole-body doses ranged from 0.67 rem to 4.75 rem. There is a small group of workers who had higher doses, perhaps as high as 100 rem. However, individual doses for the workers who developed brain cancer were not provided.

Unfortunately, most of what is known about radiation's effects on the nervous system cannot be directly compared with the Hanford situation. Current knowledge comes from studies of people exposed to high organ doses or high whole-body doses of radiation received over minutes, hours or days. In contrast, Hanford's releases resulted in some high radiation doses to the thyroid, some low doses to other organs, and low whole-body doses. These doses occurred over weeks, months or years.

While most studies of radiation's effect on the nervous system involve external exposure, most of the dose from Hanford's releases came from internal radiation exposure. People were internally exposed when they drank contaminated milk or water, or ate contaminated foods. Because the circumstances of the studies discussed above differ from the Hanford situation, the conclusions of those studies do not necessarily apply to Hanford-exposed people.

Occurrence of Nervous System Diseases

Some people believe there is a higher than usual occurrence of nervous system diseases among people exposed to Hanford's releases of radioactive materials. Determining the occurrence of nervous system diseases can be difficult. For most of these diseases, only estimates are available of the number of cases in the United States, since there are no requirements to report nervous system diseases to health officials. Little or no information has been collected about the number of cases of many of these diseases among people exposed to Hanford's releases of radioactive materials. As a result, it is not possible, with the information currently available, to determine if the occurrence of nervous system diseases among Hanford downwinders is higher than usual.

It seems to me that I would need three pieces of information to determine the answer to this question. First, it is essential to identify the specific types of radioactive materials released from Hanford from 1944 through 1972 and their known environmental cycles. Secondly, I would need to know the nervous system response to these identified radioactive materials and the various levels of exposure to the whole body and to the specific sites in the body to which these radioactive materials may migrate. Thirdly, I would need actual epidemiologic data for the neurological diseases, disorders and dysfunctions in the Hanford area and also for a similar area that was not affected by radioactive materials of the same type.

This report, while including valuable and important information, is not a carefully balanced one. It leads readers to the view that it is highly unlikely that we can determine that Hanford radiation releases were damaging to human health.

On the contrary, some respected researchers and low-level radiation experts (Drs. Ernest Sternglass and Alice Stewart) have concluded that low-level radiation exposure is extremely dangerous, much more so than some high-level radiation exposure. These views seem to run counter to conclusions made by the Sever study, cited in this report, that Hanford doses were "too low to account for the elevated rates of neural tube defects as being caused by radiation exposure."

Studies on relationships between health effects of the central nervous system and exposure to radioactive materials from sites other than Hanford could be done and could help establish such relationships in general. Also, as both Dr. Sternglass and Dr. Stewart have recommended, studies should be made comparing health risks for downwinders and for upwinders at Hanford, specifically for death rates from thyroid cancer.

1. We need information about "low-dose" radiation: (a) What is the state of the controversy within the scientific community about whether or not ANY dose of radiation is "too low to account for" some health effects? (b) Might there be a relationship between the elevated rate of neural tube defects and low-dose radiation? (c) What are the results of animal studies of internal low-dose radiation exposure?

2. We need information about Hanford radiation releases: (a) What was released, how much of it, and over what period of time? (b) I recall that in the 1970s, game bird hunting was restricted around Vale, Oregon, allegedly because of Hanford releases. What were wind/weather conditions during that time?

3. We need demographic information on the exposed population, the state of health of the nervous system of those people and a comparative study of an unexposed population.

4. We need information that is credible to those who "believe there is a higher than usual occurrence of nervous system diseases among people exposed to Hanford's radioactive releases" and that information needs to be perceived as not being biased by the Department of Energy or any agency.

This is a particularly difficult question to address, since the available information on the health effects on the central nervous system from radiation released by the Hanford facility, or any other nuclear facility, appears to be quite limited. One would need information regarding the radioactive source, such as what it was, how much was released, for how long, etc.

Given the probable radiation doses from radioactive materials released by Hanford and what is documented from populations exposed to much higher doses, I would not expect to find evidence of any radiation-related effects of the nervous system in the surrounding population.

I would, however, seriously consider the findings of any carefully controlled study of an exposed population with a reliable determination of radiation dose, and that found a clear relationship between dose and a health effect. Also, I would consider any independent evidence, not based on the disease under investigation, that radiation doses to neural tissue were on the order of tens of rad or more.

We need to know � perhaps by a random sampling/survey � the health status of the multitudes that lived in the affected area during the 1944-1972 period. For those who've died, what caused their death? What is the health condition of those still living?

HHIN asked several individuals and organizations to respond to this question: What types of information would be needed to determine whether or not a relationship exists between health effects of the nervous system and exposure to radioactive materials released by Hanford from 1944 to 1972?

Finding an association (or a link) between an exposure and a disease does not always mean there is a causal relationship (that is, an exposure causes a disease). There may be other reasons for the association.

Public health scientists consider a set of eight factors (known as Hill's postulates) to be an important guideline for proving a causal relationship. First is the strength of the association: there should be more disease in the exposed group; the higher the rate of disease in the exposed group, the more convincing the association. Second, the association should be consistent, or repeatedly observed in different studies. Third is timing: does the exposure occur before the disease, and is the latent period similar to what is already known? Fourth, the association should be dose-related: is there more disease in people who are exposed to a higher dose? Fifth, the association should be biologically plausible, consistent with current biological theory. Sixth, the association should be coherent with earlier studies, not contradicting known facts. Seventh is experiment: does a "preventive" action actually prevent the disease? Eighth is analogy: do similar exposures cause similar diseases?

Information needed: Urge downwinders to report on the basis of health questionnaires and their selected medical records. Assemble records from hospitals and clinics. Use regional hospital records for comparable farming areas not exposed to Hanford's releases, as a basis for comparison. This will not establish cause per se according to epidemiological standards. However, if the difference in rates between Hanford downwinders and other populations is large, it will certainly raise questions about a possible link. The mode for this research must include full participation of downwinders, such as described by Phil Brown in his article, "Popular Epidemiology: When the Public Knows Better" (Environment, Vol. 35, No. 8, October 1993).

1.The Hanford Environmental Dose Reconstruction Project is the only study estimating doses from radiation received by people exposed to Hanford's releases of radioactive materials. When using information from the Dose Reconstruction Project and other studies, readers should keep in mind that research results depend on a number of factors, such as the information available, and the methods and type of analysis used.

2. Fred A. Mettler and Robert Moseley, Jr. Medical Effects of Ionizing Radiation. San Diego: Grune and Stratton, 1985.

3. Elaine Ron et al. "Tumors of the Brain and Nervous System After Radiotherapy in Childhood." The New England Journal of Medicine; Vol. 319, No. 16, 1988, pp. 1033-1039. Ron is a radiation epidemiologist at the National Cancer Institute in Bethesda, Md.

4. National Research Council. Health Effects of Exposure to Low Levels of Ionizing Radiation (commonly known as BEIR V�the report of the fifth Committee on the Biological Effects of Ionizing Radiation). Washington, DC: National Academy Press, 1990.

5. Shoji Tokuoka and Masayoshi Tokunaga. "Site-Specific Cancer Incidence: An Interim Report." RERF Update; Spring 1995, pp. 6-7. Tokuoka and Tokunaga are with the Department of Epidemiologic Pathology, Radiation Effects Research Foundation (RERF), Japan.

6. Desmond Thompson et al. "Cancer Incidence in Atomic Bomb Survivors, Part II: Solid Tumors, 1958-1987." Radiation Research, Vol. 137, 1994, pp. S17-S67.

7. BEIR V.

8. Mettler and Moseley.

9. Ron et al.

10. Mettler and Moseley.

11. Ron et al.

12. Lowell E. Sever et al. "A Case-Control Study of Congenital Malformations and Occupational Exposure to Low-Level Ionizing Radiation." American Journal of Epidemiology; Vol. 127, No. 2, 1988, pp. 226-242. At the time of this study, Sever was with the Division of Birth Defects and Developmental Disabilities, Center for Environmental Health, Centers for Disease Control in Atlanta, Ga.

13. Lowell E. Sever et al. "The Prevalence at Birth of Congenital Malformations in Communities near the Hanford Site." American Journal of Epidemiology; Vol. 127, No. 2, 1988, pp. 243-254.

14. Victor Alexander. "Brain Tumor Risk Among United States Nuclear Workers." Occupational Medicine: State of the Art Reviews. Philadelphia: Hanley and Belfus, Inc., Vol. 6, No. 4, October-December, 1991, pp. 695-714. Alexander is a researcher with EnviroMedicine Associates in New Orleans, La.

Genetic Effects and Birth Defects from Radiation Exposure,