A sign on a desert road reads “Contaminated Area. Ground Surfaces Contaminated. Stay on Roadway to Next Junction. Radiological Science Dept.”
A sign at Hanford warning of contamination.



The human toll of the Manhattan Project reached beyond the Japanese people killed in the atomic bombings of Hiroshima and Nagasaki. Production and testing of the world’s first atomic weapons released enormous quantities of radioactive byproducts into the environment. Individuals living near the Manhattan Project sites at Hanford, Washington; Los Alamos, New Mexico; and Oak Ridge, Tennessee were unknowingly subjected to these radioactive environmental toxins. These people would eventually identify themselves as the “Downwinders.” 

In the rush to build the bombs, plant operators expelled radioactive byproducts from uranium enrichment at Oak Ridge and plutonium production at Hanford into the local atmosphere and waterways. The July 1945 Trinity test in the New Mexico desert south of Los Alamos deposited fallout on Native American communities, farmers, and livestock over hundreds of miles. Years, sometimes decades later, Manhattan Project Downwinders mysteriously developed cancers, thyroid disease, infertility and sterility. Women experienced stillbirths and children with congenital health defects.  

Some people living downwind were more at risk than others. Infants and children who drank fresh milk from local cows ingested radioactive iodine, as did families who grew and ate their own vegetables. Farmers and agricultural laborers downwind from Hanford inhaled various radioactive isotopes dusted on vegetation. Tribal peoples consumed irradiated fish as well as game. Pregnant women who consumed locally-produced food exposed their unborn babies.

Due to the secrecy surrounding the Manhattan project, officials did not warn local residents about radioactive pollution and dismissed the concerns that some individuals expressed. Only in the 1980s were journalists, concerned citizens, and Downwinder activists able to obtain US Department of Energy documentation confirming the harm that had occurred.  

Click on the articles below to learn more about Downwinders 

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    Last updated: February 14, 2024

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    Manhattan Project National Historical Park
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