Savannah River Site Health Effects Subcommittee (SRSHES) Meeting

Final Meeting Minutes
June 06, 2002

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In Phase III, radionuclides released from the site that were of highest significance relative to human health effects will be determined. IAEA Safety Report Series No. 19 is being considered as the data source in this effort. The report describes generic models that can be used to assess the impact of discharges of radioactive substances to the environment. Pathways that can be considered in a screening analysis or dose assessment include atmospheric releases that can eventually be inhaled or ingested through food or water. The basic screening model will calculate the activity released, multiplied by dispersion factors in the environment, multiplied by a food transfer factor, multiplied by a human usage factor, and multiplied by a dose factor.

Two major data sources will be used to develop the Phase III screening model for exposure years 1955 through 1992. First, information gathered in Phase II will include radionuclides released; locations or release points of SRS releases; and annual amounts of each radionuclide released from each release point. Second, information on the exposed human population will include distance from release points; amount of air breathed; amount and source of potentially contaminated food and water ingested; and fraction of time spent outdoors for various activities. Default usage factors will be applied in the screening model for data that cannot be gathered on the exposed human population.

Since IAEA is being considered as the Phase III data source to determine health effects from radionuclide releases, 2001 IAEA screening assumptions for milk intake, meat intake and breathing rate have been demonstrated to be consistent with those established by the U.S. Department of Agriculture in 1974. Screening scenarios are generally developed to represent typical members of the population, since lifestyles, cultural practices and other factors vary among individuals. To account for population differences, certain types of data will be collected for each screening scenario, such as age; location of residence, work, school, food sources and other activities; amount of foods consumed; breathing rate; and percent of time spent outdoors on various activities. Milk will be particularly emphasized as a food source in the screening scenarios.

CDC is currently considering six screening scenarios for Phase III of the dose reconstruction project. The rural family would have lived in the closest downwind area where farms could have been located in 1955. Adults as well as infants born in 1955 and 1964 will be considered since 1964 was the year of the highest radioiodine release. Reasonable and high default consumption values will be used. Persons would have spent a lot of time outdoors, extensively worked in the soil, consumed fresh milk from a backyard cow, and had crops irrigated from the Savannah River.

The urban/suburban family would have lived just downwind of the site boundary where urban/suburban families could have lived in 1955. Adults, infants and consumption values will be the same as those for the rural family. Persons would have worked at the nearest downwind industrial location in 1955 and consumed fresh milk from the nearest dairy or rural neighbor. The migrant worker family would have lived in the nearest downwind location where migrant workers could have lived and worked in 1955. Adults, infants and consumption values will be the same as those for the rural family. Persons would always have been outdoors and in contact with the soil; had crops irrigated by the Savannah River; and obtained food from local farms or grocery stores.

The houseboat family would have lived at the nearest docking location downwind where persons could have lived on houseboats in 1955. Adults, infants and consumption values will be the same as those for the rural family. Persons would always have been outdoors, in contact with the Savannah River and obtained food from local farms or grocery stores. The delivery person scenario has the same assumptions as adults in the urban/suburban family, but spends eight hours per week onsite.

The outdoors person would have lived in camps at the nearest downwind location that was appropriate for the season, i.e., hunting or fishing. Consumption values will be the same as those for the rural family. Persons would always have been outdoors; spent eight hours per day on the Savannah River in the summer; spent eight hours per day onsite during hunting or fishing season; and obtained food from nearby grocery stores. The study area for the SRS dose reconstruction project has been defined as 50 miles around the perimeter of the site; various counties and the downstream portion of the Savannah River are covered in the study area.

CDC previously asked SRSHES to consider the appropriateness of the scenarios; recommend locations of residences, schools, work, food sources and other activities; and suggest other reasonable scenarios for the target populations. SRSHES formed the Scenario Workgroup in response to this request. The members met in January 2002 to initiate the process of providing input to CDC on each acceptable scenario. Other progress on the Phase III activities include CDC’s contract with Advanced Technology Laboratory International to conduct the screening analysis. The contractor will closely collaborate with the Scenario Workgroup and incorporate recommendations by SRSHES in the screening analysis.

Discussion.
Dr. Crawford inquired whether geographic locations associated with the scenarios have been selected. Dr. Whitcomb replied that the Scenario Workgroup will assist in this effort, such as identifying cattle and horse ranches near SRS for the migrant worker family scenario. Dr. Umansky emphasized the importance of considering persons of different ages in the scenarios. For example, older individuals would have been exposed for longer periods of time, while younger persons with rapid cell growth would have more potential for damaging health effects.

Dr. Whitcomb confirmed that the ages of individuals are definitely being considered during the scenario development process. Ms. Kato questioned the rationale for applying IAEA standards in the screening analysis since SRS employees are physically larger than an average international population. She also noted that the proposed screening scenarios presented by Dr. Whitcomb do not reflect additions, changes and other recommendations SRSHES made during the previous meeting.

Dr. Whitcomb clarified that default values used by IAEA are only being considered at this point. The Scenario Workgroup has been asked to provide site-specific information that may differ from the IAEA screening assumptions and be more reasonable for the SRS area. The workgroup is also considering other usage factors. He added that the screening scenarios are still in the development stage; the final product by the workgroup will reflect changes and other recommendations made by SRSHES.

Dr. Bustos planned to discuss the time-line of activities with Mr. Lockridge, the Scenario Workgroup Chair. He wanted to ensure that progress in developing the screening scenarios was not delayed. Dr. Wilson asked about the process to determine a downwind location, such as the direction the wind blows on a particular day. Dr. Whitcomb explained that in developing some screening scenarios, the wind is forced to blow 25% of the time and in a particular downwind direction during a given year. The actual scenarios are unrealistic, but the calculations are based on existing data.