food and air. Most is in the skeleton. The biochemistry of depleted uranium is the same as natural uranium. Radiological hazards The primary radiation danger from pure depleted uranium is due to alpha particles, which do not travel far through air, and do not penetrate clothing. However, in a matter of a month or so, a sample of pure depleted uranium will generate small amounts of thorium-234 and protactinium-234, which emit the more penetrating beta particles at almost the same rate as the uranium emits alpha particles. This is because uranium-238 decays directly to thorium-234, which with a half-life of 24 days decays to protactinium-234, which in turn decays in a matter of hours to the long-lived uranium-234. A quasi-steady state is therefore reached within a few multiples of 24 days. Available evidence suggests that the radiation risk is small relative to the chemical hazard. Surveying the veteran-related evidence pertaining to the Gulf War, a 2001 editorial in the BMJ concluded that it was not possible to justify claims of radiation-induced lung cancer and leukaemia in veterans of that conflict. While agreeing with the editorial's conclusion, a reply noted that its finding in the negative was guaranteed, given that "global dose estimates or results of mathematical modelling are too inaccurate to be used as dose values for an individual veteran", and that, as of April 2001, no practical method of measuring the expected small doses that each individual veteran would receive had been suggested. The author of the reply, a radiation scientist, went on to suggest a method that had been used several times before, including after the 1986 Chernobyl accident. Despite the widespread use of DU in the Iraq War, at least a year after the conflict began, testing for UK troops was still only in the discussion phase. The Royal Society Working Group on the Health Hazards of Depleted Uranium Munitions (RSDUWG) concluded in 2002 that there were "very low" health risks associated with the use of depleted uranium, though it also ventured that, "[i]n extreme conditions and under worst-case assumptions" lung and kidney damage could occur, and that in "worst-case scenarios high local levels of uranium could occur in food or water that could have adverse effects on the kidney". In 2003, the Royal Society issued another urgent call to investigate the actual health and environmental impact of depleted uranium. The same year, a cohort study of