Trinity Fallout Reached 46 States, Study Finds
A new reconstruction shows radioactive material from the 1945 New Mexico test spread across most of the continental United States within 10 days.
Updated on Nov. 6, 2026 in Nuclear
A study published August 24, 2026 in Scientific Reports reconstructs fallout from the Trinity test, which detonated at 5:29 AM local time on July 16, 1945, finding deposition reached 46 US states within 10 days. Only Washington and Oregon showed no fallout deposition in the model.
Why it matters
The reconstruction offers a revised picture of nuclear fallout exposure across the United States, showing the reach of early atmospheric testing extended far beyond the test site. The findings add detail to long-running questions about population-level radiation exposure from weapons testing.
The authors ran HYSPLIT 104 times with 9 million particles per run, revising the Trinity yield to 24.8 kilotons from a previous 21-kiloton estimate. The reconstruction covered 94 of 101 US atmospheric tests, and the study did not resolve all uncertainty in the deposition estimates.
The players
Sébastien Philippe
Lead author of the Scientific Reports study reconstructing Trinity test fallout deposition across the United States.
The details
Researchers led by Sébastien Philippe combined NOAA's HYSPLIT transport model with ERA5 weather data to trace fission products from the Trinity detonation. Contamination was also found on strawboard used to package X-ray film in Indiana and Iowa in 1945.
Timeline
July 16, 1945: Trinity device detonated in New Mexico at 5:29 AM local time.
2016: A Federal Register notice laid out the National Cancer Institute dose plan.
2020: The National Cancer Institute published its New Mexico Trinity fallout study.
August 24, 2026: The reconstruction study was published in Scientific Reports.
Historical Context
The 2020 National Cancer Institute New Mexico Trinity fallout study focused on exposure near the test site, while the new reconstruction maps deposition well beyond New Mexico. Together they revise the geographic scope of early US atmospheric testing fallout.
The reconstruction clarifies how far radioactive material from early weapons testing may have traveled across the country. Readers interested in historical exposure questions can follow how agencies have studied Trinity fallout.
The takeaway
Early atmospheric nuclear tests spread fallout far beyond their immediate sites, and newer modeling is helping map that reach. Readers can track how scientists refine these reconstructions as more data becomes available.
Further reading
Explore more on Nuclear research and fallout history.
Source note: This article includes information reported by The Times of India.
