This is an investigation which was aired on the BBC INSIDE OUT programe on Monday 6th Novemeber 2006.. br Between 1953 and 1964 top secret trials were carried out using a chemical concoction of zinc cadmium sulphide to simulate how a cloud would disperse biological agents. br br The unsuspecting population in the East of England was sprayed covertly with the poisonous compound at least 76 times.