Hanford Environmental Dose Reconstruction (HEDR) Project (most portions completed, 1995)

Purpose:

Investigate the amount and types of radioactive materials Hanford released between 1944 and 1972, and how these materials may have moved through the environment and exposed people, and estimate the radiation doses people received.

Results:

A large part of the dose reconstruction work is complete. The HEDR Project found that Hanford released more than 200 different kinds of radioactive elements (radionuclides). However, the study concluded that only some of these are likely to have had an effect on people. The HEDR Project calculated dose estimates for representative (typical) individuals and published summary results in April 1994.

For Hanford's releases into the air, the HEDR Project concluded that more than 98 percent of the radiation doses that most people outside Hanford's boundaries received came from iodine-131. Almost all the iodine-131 releases to the air occurred from December 26, 1944 through the end of 1957. The most important exposure pathway for iodine-131 was milk from cows and goats that fed on pasture downwind of Hanford. In the study's representative dose estimates, the highest radiation doses were to children who lived closest to Hanford between 1944 and 1951, and who drank milk from local cows fed on fresh pasture. The study also calculated cumulative representative doses for five other radionuclides released to the air. These are cerium-144, ruthenium-103, ruthenium-106, strontium-90 and plutonium-239.

Regarding Hanford's radioactive releases to the Columbia River, the HEDR Project concluded that the largest releases occurred between 1950 and 1971 and that five radionuclides contributed the most to dose. These are sodium-24, phosphorus-32, zinc-65, arsenic-76 and neptunium-239. The most important exposure pathway was the consumption of non-migratory fish species. People also were exposed by drinking contaminated water, eating contaminated shellfish or waterfowl, spending time along the shoreline or swimming in contaminated stretches of the river. Current estimates suggest that these routes contributed less to dose than did consumption of fish.

Some scientific work for the HEDR Project is still underway. See HEDR Project - Task Completion.

Methods:

The HEDR Project studied Hanford's air releases and exposures in a 75,000-square-mile area, including parts of Washington, Oregon and Idaho. The study of releases to the Columbia River included counties along the river from Hanford to Pacific coastal areas. Most of the dose reconstruction work was conducted between 1987 and 1995, long after the releases occurred. HEDR scientists used a wide range of historical records. These included Hanford's production and monitoring records; weather information; census and demographic information on where people lived, worked, farmed and fished, and their lifestyles and diet; and information about milk production and distribution. Where there were gaps in the information, the study scientists conducted additional research. Using this research, HEDR scientists created complex computer models to estimate radiation doses to people in the areas studied.

Investigators and sponsors:

Battelle Pacific Northwest Laboratories in Richland, Wash., conducted the scientific work. An independent Technical Steering Panel oversaw the project from 1988 through 1995. Funding source: The U.S. Department of Energy (USDOE) funded the study from 1987 to 1992, when funding authority was transferred to the Centers for Disease Control and Prevention (CDC).

 

 

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