The US carried out the last of its 67 nuclear weapons tests on the Marshall Islands more than 60 years ago. New research by Columbia University’s K=1 Project, directed by Ivana Nikolic Hughes, shows that contamination on several of the northern islands continues to exceed safety standards set by many countries, as well as the maximum level of radiation agreed upon in a memorandum of understanding between the US and the Republic of the Marshall Islands (Proc. Natl. Acad. Sci. U.S.A. 2019, DOI: 10.1073/pnas.1903421116 and DOI: 10.1073/pnas.1903481116). On several islands, the radioactivity in the soil exceeds that found near more recent disaster sites, including Chernobyl, Ukraine, and Fukushima, Japan—up to 1,000 times as great in some areas. Nikolic Hughes notes that Marshallese people often travel to uninhabited islands to collect food, so previous work that focused on inhabited islands may have underestimated their exposures. The team also found radioactivity in a coconut crab, raising the concern of contamination further up the food chain. The exact health risks of this radiation are unknown, but the researchers’ next step is to look for a correlation between mutation levels in local fauna and radioactivity, potentially giving insight into how the local populations might be affected.