Booker repeatedly claimed that white asbestos is "chemically identical to talcum powder" and poses a "non-existent" risk to human health, relying primarily on a 2000 paper for the Health and Safety Executive (HSE). He wrote in January 2002 that "HSE studies, including a paper by John Hodgson and Andrew Darnton in 2000, concluded that the risk from the substance is "virtually zero". In response, the HSE's Director General, Timothy Walker, wrote that Booker's articles on asbestos had been "misinformed and do little to increase public understanding of a very important occupational health issue." The HSE issued further rebuttals to articles written by Booker in both 2005 and in 2006.