The July/August issue of Arms Control Today on page 16 incorrectly reported the 1957 fallout plume of a Soviet tank explosion containing highly radioactive waste. The correct figure is about 15,000 square kilometers. The article also incorrectly described the Snake River Aquifer. It is southeastern Idaho’s sole source aquifer. In addition, the article incorrectly identified the period nuclear tests were conducted. Testing started in 1945 and continued to the end of the 21st century.