ATSDR - Testimony: Medical Monitoring at Hanford Nuclear Facility

Congressional Testimony
Medical Monitoring at Hanford Nuclear Facility

Testimony of
Barry L. Johnson, Ph.D.
Assistant Surgeon General
Assistant Administrator
Agency for Toxic Substances and Disease Registry
Public Health Service
U. S. Department of Health and Human Services

Before the
Permanent Subcommittee on Investigations
Committee on Government Affairs
United States Senate

September 16, 1998

Good morning. I am Barry Johnson, Ph.D., Assistant Administrator of the Agency for Toxic Substances and Disease Registry (ATSDR). I am accompanied by Jeffrey Lybarger, M.D., Director, Division of Health Studies.

Our testimony today will address ATSDR's medical monitoring responsibilities under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund. In particular, we will describe ATSDR's finding that medical monitoring of persons exposed to radioactive iodine released, in the past, from the Hanford nuclear facility in Richland, Washington is called for under CERCLA. Our testimony also relates the public health approach taken by ATSDR in considering CERCLA's medical monitoring provisions when populations have been exposed to hazardous substances released into the environment. Further, because the Institute of Medicine (IOM) recently recommended against thyroid cancer screening, we will highlight our differences in decision making and why we continue to support our decision for a medical monitoring program for a subpopulation of well-defined persons exposed as children to iodine-131 released from the Hanford facility.

ATSDR interprets its CERCLA language on medical monitoring as an important public health intervention that provides early diagnostic and referral services for a well-defined population at health risk. Early detection of a change in health status is the most effective way to lessen the burden of more advanced disease and enhances survival. ATSDR's public health approach for considering a population for medical monitoring involves a rigorous process that

In 1995, ATSDR commenced a deliberative process to determine if medical monitoring was warranted for persons at increased risk of thyroid cancer and other conditions from exposure to iodine-131 released from the Hanford Nuclear Reservation during the period, 1945 through 1951. A dose reconstruction study had documented large releases of iodine-131 into the atmosphere and provided dose estimates of representative individuals according to their age and where and when they lived within a large geographic area surrounding Hanford. From these data, ATSDR determined that the major public health risk is among young children downwind of the facility who consumed contaminated milk during the period, 1945 through 1951.

Early in our efforts, ATSDR and CDC jointly formed the Hanford Health Effects Subcommittee (HHES) to advise the agencies on their research and public health activities related to the Hanford facility. This committee comprises 21 persons who represent community, business, government and other interests. Our meetings are held on a quarterly basis, in public, and generate considerable media attention. We also work closely with the Intertribal Council on Hanford Health Projects, which included representation from 9 tribal nations in the Hanford region. The HHES provides an essential resource for expressing health concerns from communities and tribal nations. They reviewed ATSDR's approach to, and findings from, the consideration of a medical monitoring program.

Exposure and Related Health Outcomes - In consultation with an expert panel, we determined that a median 10 rad, or higher, thyroid dose estimate for children would place these individuals at significant increased risk. This is based on the extensive medical literature of external radiation exposures that support elevated thyroid cancer risks at this dose level, or higher, among children. These elevated thyroid cancer risks occur for many decades (at least 40 years or more) following radiation exposures to the head and neck in childhood. The literature also suggests that there are other health outcomes that might be related to thyroid radiation exposures, including hypothyroidism, chronic lymphocytic thyroiditis, and hyperparathyroidism.

Moreover, there is an increasing amount of medical literature that supports a reasonable association between radioactive iodine exposures and excess occurrences of thyroid neoplasms. This literature includes published studies of populations exposed to the Chernobyl reactor fire in 1986, Marshall Islanders exposed to the 1954 BRAVO test releases, schoolchildren exposed to Nevada Test Site atmospheric testing releases during the period 1951 through 1962, and preliminary findings from the Hanford Thyroid Disease study.

Target Population - Our analysis estimates that 14,000 people (majority were exposed in 1945) would have received a sufficient thyroid dose as children and placed them at significant risk of thyroid cancer and other thyroid and parathyroid conditions.

ATSDR Review Process - After 18 months of careful consideration and analysis, following meetings with executive and senior scientific staff and a meeting with community and tribal representatives, Dr. David Satcher, as the former ATSDR Administrator and Director of the CDC, signed the decision memo on February 7, 1997, to implement the program, pending funding from the DOE.

ATSDR is directed under CERCLA to perform medical monitoring programs for populations at significant risk of adverse health effects from exposure to hazardous substances. This represents a different type of public health activity than the setting of national policy or standards for thyroid cancer screening.

We perform our work on a site-specific basis using the best available scientific and medical information and following a rigorous process that is based on our seven criteria for medical monitoring. We not only involve the affected public in our decision making process, but also conduct external scientific peer review of our work to make the best public health decision possible. By consulting recognized experts in the medical issue under consideration and involving the public most directly affected by the proposed intervention, our process provides an important and necessary balance for public health decision-making.

We agree with the IOM/NAS that the current dose estimates for U.S. counties have large uncertainties, which makes it difficult to readily determine who was at highest risk. At Hanford, however, we are fortunate that the dose reconstruction study estimated doses at a much more precise level of geographic resolution (6-mile by 6-mile areas) and our eligible population includes 60% who received thyroid dose estimates of 25 rad or higher.

As a final note, ATSDR successfully implemented a screening program for persons exposed to a human bladder carcinogen. This was initiated more than 10 years ago, based on the known science at the time, and on good public health practice.

In 1986, ATSDR funded its first such program for former workers at the Drake Chemical site in Pennsylvania. These workers had been exposed to betanaphthylamine a known human carcinogen, specifically linked to bladder cancer. A total of 364 workers were initially eligible for screening; 82% of whom chose to participate. Compliance continues to be high with participation rates ranging between 82% to 92%. Of the workers screened in the first phase, 50 have been referred for the second phase which includes a laboratory diagnostic work-up (a cystoscopy). As of 1997, two workers have been diagnosed as having early stage cancer, another 13 were diagnosed with varying degrees of dysplasia, and 25 had some type of bladder abnormality diagnosed. This program has clearly been of benefit for detection and treatment of disease for these workers, and has been so successful that it now is continued by the state of Pennsylvania.

ATSDR considers medical monitoring of a well-defined high risk population to be consistent with the central principle of public health: prevention of disease is preferable to treatment and medical care, and early loss of life.

Our testimony today will address ATSDR's health surveillance responsibilities under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund. In particular, we will describe ATSDR's finding that health surveillance of persons exposed to radioactive iodine released, in the past, from the Hanford nuclear facility in Richland, Washington is called for under CERCLA. Our testimony also relates the public health approach taken by ATSDR in considering CERCLA's health surveillance provisions when populations have been exposed to hazardous substances released into the environment. In view of the recent recommendation of the National Academy of Sciences's Institute of Medicine (IOM/NAS) against thyroid cancer screening, we will also highlight our differences in decision making and why we continue to support our decision for a medical monitoring program for a subpopulation of persons exposed as children to iodine-131 released from the Hanford facility.

As background, ATSDR was created by Congress to address the public health implications of hazardous waste sites and unplanned releases of hazardous substances into community environments. ATSDR works closely with the U.S. Environmental Protection Agency (EPA), other federal agencies, states, communities, and tribal nations in the conduct of our CERCLA responsibilities.

ATSDR's public health responsibilities under CERCLA include conducting public health assessments and attendant activities at all sites on the National Priorities List (NPL). There are four NPL sites at the Hanford nuclear facility. ATSDR was led to consider health surveillance of Hanford populations through our evaluation of environmental contamination data provided to us by the Department of Energy (DOE) and state agencies, as well as findings from the Hanford Environmental Dose Reconstruction project. Based primarily on consumption of milk contaminated with iodine-131, thyroid dose estimates were highest for young children during the period, 1945 through 1951. The dose reconstruction findings were prepared for the Centers for Disease Control and Prevention (CDC) and published in 1994.¹

With regard to ATSDR's mandated responsibility for health surveillance, CERCLA [42 USC 9604,§104(i)(9)] states, in part,

ATSDR interprets the cited statutory language as an important public health intervention strategy that provides early diagnostic and referral services for a well-defined population at health risk. Early detection of a change in health status is the most effective way to lessen the burden of more advanced disease and enhances survival. ATSDR's public health approach for considering a population for health surveillance involves a rigorous process that

In February 1997, ATSDR concluded its determination that a medical monitoring program was warranted for persons at significant increased risk of thyroid cancer and other conditions from exposure to iodine-131 released from the Hanford Nuclear Reservation during the period, 1945 through 1951. In south central Washington State, the Hanford facility produced the plutonium used in American nuclear weapons. During a chemical separations process, primarily during 1945, iodine-131 was released to the atmosphere. As previously mentioned, a dose reconstruction study documented large releases of iodine-131 into the atmosphere and provided dose estimates of representative individuals according to their age and where and when they lived within a large geographic area surrounding Hanford. ATSDR determined that the major public health risk is among young children downwind of the facility who consumed contaminated milk during the period, 1945 through 1951.

In order to make the public health decision about Hanford, ATSDR used its medical monitoring criteria to determine the appropriateness of health surveillance of thyroid disease for persons exposed to radioactive iodine released from the Hanford facility. A summary of the seven criteria is provided as an attachment. They were developed with input from the public and technical experts and endorsed by ATSDR's Board of Scientific Counselors. In applying the criteria to Hanford, ATSDR used a review process that involved a variety of experts, as well as several representatives of the community and tribal populations impacted. In particular, ATSDR and CDC jointly formed the Hanford Health Effects Subcommittee (HHES) to advise the agencies on their research and public health activities related to the Hanford facility. ATSDR and CDC also worked closely with the Intertribal Council on Hanford Health Projects, which included representation from 9 tribal nations in the Hanford region. The HHES provided an essential resource for expressing health concerns from communities and tribal nations. They reviewed ATSDR's approach to, and findings from, the consideration of a medical monitoring program.

We will briefly discuss several key points related to the medical monitoring decision for persons exposed to radioactive iodine released from the Hanford nuclear facility. ATSDR has published an extensive report that provides important background and details of the medical monitoring program associated with the Hanford nuclear facility³. We can make these documents available to the subcommittee, if that would be of assistance.

Exposure and Related Health Outcomes - As stated in this testimony, CERCLA directs the Administrator of ATSDR to initiate a health surveillance program for populations at significant increased risk of adverse health effects as a result of exposure to hazardous substances released from a facility. The law further defines this program as a periodic medical testing to screen people at significant increased risk for disease. From our expert panel we determined that a median 10 rad, or higher, thyroid dose estimate for children would place these individuals at significant increased risk. This is based on the extensive medical literature of external radiation exposures that support elevated thyroid cancer risks at this dose level, or higher, among children. These elevated thyroid cancer risks occur for many decades (at least 40 years or more) following radiation exposures to the head and neck in childhood. The literature also suggests that there are other health outcomes that might be related to thyroid radiation exposures, including hypothyroidism, chronic lymphocytic thyroiditis, and hyperparathyroidism. Moreover, there is an increasing amount of medical literature that supports a reasonable association between radioactive iodine exposures and excess occurrences of thyroid neoplasms. This literature includes published studies of populations exposed to the Chernobyl reactor fire in 1986, Marshall Islanders exposed to the 1954 BRAVO test releases, and schoolchildren exposed to Nevada Test Site atmospheric testing releases during the period, 1951 through 1962.

Target Population - One of the ATSDR's medical monitoring criteria requires a well-defined, identifiable population at-risk with sufficient levels of exposure. The Hanford dose reconstruction study conducted for CDC assisted ATSDR in defining an eligible population. The thyroid dose estimates for Hanford were determined for 6-mile by 6-mile grids within a 75,000 square mile region around Hanford. ATSDR estimates that 14,000 people (majority were exposed in 1945) would have received a sufficient thyroid dose as children to place them at significant risk of thyroid cancer and other thyroid and parathyroid conditions. ATSDR will be able to locate these individuals by various methods using birth certificates, contacting ongoing and previous study participants, and other tracing methods. Our tracing efforts of historical residents for other ATSDR studies have successfully located 85% or more of the eligible population. In addition, CDC has traced and located over 85% of their Hanford thyroid morbidity study participants who were young children at the time of exposure.

If the entire eligible population participates in the program, ATSDR estimates that 90 thyroid cancers will be detected through the first round of the medical monitoring program, versus eight thyroid cancers that would be expected without such a program. From our review of the scientific and medical literature, there is evidence that suggests early detection and treatment of thyroid disease can save lives, reduce chronic health conditions, and lessen the chance of thyroid cancer recurrence.

Prevention Effectiveness Approach - Because there is no randomized controlled study proving the benefits of thyroid cancer screening, ATSDR conducted a prevention effectiveness analysis to project the potential harms and benefits of a program based on a clinical decision model. The model used program scenarios with different eligible populations and methods of medical evaluation and compared the findings to a no-program scenario. The model generated estimates of the number of thyroid nodules, biopsies, surgeries, thyroid cancers, and thyroid cancer deaths averted for each scenario. The analysis helped determine which population subgroups and methods of medical evaluation would result in the most benefits and fewest harms to those who might participate in a medical monitoring program. Prevention effectiveness analysis helped identify a well-defined, high risk population that could benefit from a program. Using a range of thyroid dose estimates, the analysis showed medical monitoring of persons having thyroid dose estimates of 10 rad or greater as children would yield a higher rate of thyroid cancers detected early and lives saved. The analysis also showed that extending the more precise geographic region of program eligibility to county boundaries resulted in large numbers of lower risk people (with lower thyroid dose estimates) being evaluated and being put at greater risk of harm and false positive diagnoses. The prevention effectiveness analysis also allowed us to project which benefits and harms might result from various medical monitoring program scenarios. Clearly, a well-defined high risk population must be identified for a program with thyroid evaluation to derive the most benefit. The geographic precision of the radiation dose estimates from Hanford releases was a key in ATSDR's prevention effectiveness analysis and helped clearly define the at-risk target population.

ATSDR Review Process - After 18 months of careful consideration and analysis, the ATSDR proposed program underwent an extensive review process using interagency technical reviews (CDC and ATSDR), external scientific peer reviews (included four experts in clinical endocrinology, occupational and environmental medicine, disease prevention services, and preventive medicine and community health), comments from the public, and a senior and executive management public health science and policy review. The review process strengthened our finding that the program has genuine merit (for a well-defined high risk population) and should be implemented under our CERCLA responsibilities. Following meetings with executive and senior scientific staff and a meeting with community and tribal representatives, Dr. David Satcher, as the former ATSDR Administrator and Director of the CDC, signed the decision memo on February 7, 1997 to implement the program, pending funding from the DOE.

ATSDR is directed under CERCLA to perform health surveillance programs for populations at significant risk of adverse health effects from exposure to hazardous substances. This represents a different type of public health activity than the setting of national policy or standards for thyroid cancer screening.

We perform our work on a site-specific basis using the best available scientific and medical information and following a rigorous process that is based on our seven criteria for medical monitoring. We not only involve the affected public in our decision making process, but also conduct external scientific peer review of our work to make the best public health decision possible. By consulting recognized experts in the medical issue under consideration and involving the public most directly affected by the proposed intervention, this process provides an important and necessary balance for public health decision-making.

Because we are not setting national screening policy, our criteria do not require a randomized controlled study showing the benefits of screening. The expectation of such evidence by IOM is understandable, especially for a national screening policy. However, for ATSDR's targeted medical monitoring of a well-defined, high risk population we took the approach of using a weight-of-evidence. Such a screening approach is typically used in public health programs, for example lead screening for children. Virtually all public health experts would agree that lead screening programs in communities known to have high contaminations of lead have resulted in early detection and treatment of lead poisoning in our children. We believe that a targeted thyroid screening program for people at lifelong risk from Hanford exposures will derive similar benefits. ATSDR will conduct ongoing evaluations of its program to assess risks and harms -- including an expert panel review prior to initiating any medical monitoring activities -- in addition to determining how many thyroid conditions are diagnosed and treated.

We agree with the IOM/NAS that the current dose estimates for U.S. counties have large uncertainties, which makes it difficult to readily determine who was at highest risk. Other approaches might help define the highest risk population, for example a focus on young children who drank goats' milk in certain regions of the country during the release period. At Hanford, however, we are fortunate that the dose reconstruction study estimated doses at a much more precise level of geographic resolution (6-mile by 6-mile areas) and our eligible population includes 60% who received thyroid dose estimates of 25 rad or higher. Based on our ability to clearly define and locate the high risk population, our decision for medical monitoring is appropriate from a public health practice perspective.

In 1986, ATSDR funded its first such program for former workers at the Drake Chemical site in Pennsylvania. These former workers had been exposed to betanaphthylamine a known human carcinogen, specifically linked to bladder cancer. A total of 364 workers were initially eligible for screening; 82% of whom chose to participate. Compliance continues to be high with participation rates ranging between 82% to 92%. Of the workers screened in the first phase, 50 have been referred for the second phase which includes a laboratory diagnostic work-up (a cystoscopy). As of 1997, two workers have been diagnosed as having early stage cancer, another 13 were diagnosed with varying degrees of dysplasia, and 25 had some type of bladder abnormality diagnosed. This program has clearly been of benefit for detection and treatment of disease for these workers, and has been so successful that it now is continued by the state of Pennsylvania.

Our testimony today has described ATSDR's health surveillance responsibilities under CERCLA. We have presented our agency's findings that medical monitoring for thyroid disease is required for persons who were exposed as children to Hanford iodine-131 releases and received sufficiently high thyroid doses. ATSDR considers medical monitoring of a well-defined high risk population to be consistent with the central principle of public health: prevention of disease is preferable to treatment and medical care, and early loss of life. Furthermore, we believe that ATSDR's mandate under Superfund carries a clear responsibility to deal with exposures of children to iodine-131 releases from Hanford during the period, 1945 through 1951, and provide medical evaluation that can lead to early detection and mitigation of disease. Our proposed medical monitoring program at Hanford is based upon the best available science, and we believe it represents sound public health policy decision made almost 2 years ago.

Mr. Chairman, we would be pleased to answer any questions that you or subcommittee members may have.

Medical monitoring is periodic medical testing to screen persons at significant increased risk for disease. All seven criteria must be met before a program is recommended.

Copies of ATSDR documents are available from the ATSDR Information Center.
Call toll-free 1 (888) 42-ATSDR or e-mail ATSDRIC@CDC.GOV