The fire burned for three days and released radioactive fallout which spread across the UK and the rest of Europe. The radioactive isotope iodine-131, which may lead to cancer of the thyroid, was particularly concerning at the time. It has since come to light that small but significant amounts of the highly dangerous radioactive isotope polonium-210 were also released. It is estimated that the radiation leak may have caused 240 additional cancer cases, with 100 to 240 of these being fatal. At the time of the incident no one was evacuated from the surrounding area, but milk from about of nearby countryside was diluted and destroyed for about a month due to concerns about its exposure to radiation. The UK government played down the events at the time and reports on the fire were subject to heavy censorship, as Prime Minister Harold Macmillan feared the incident would harm British-American nuclear relations.