A spate of recent deaths of New York police and fire officers who took part in the emergency operation at Ground Zero after the 9/11 attacks has heightened fears that it could be the start of a delayed epidemic of cancer-related illness. Five firefighters and police officers, all of whom were involved in the rescue and clear-up at the site of the collapsed Twin Towers, have died of cancer in the past three months, the oldest being 44. Three died last month within a four-day period. Up to 70,000 people took part in the massive operation at Ground Zero, including police, firefighters and construction workers who came to New York voluntarily from all over the US. Many worked for months amid a toxic soup of dust and chemicals. Amid the pollutants within the giant pile of 1.8m tons of debris and the surrounding air were ... about 1,000 tons of asbestos that was used in the construction of the Twin Towers, pulverised lead from computers, mercury and highly carcinogenic by-products from the burning of plastics and chlorinated chemicals. No official tally is available for the number of those who have died as a result of the 9/11 clear-up. The New York state health department has recorded 817 deaths of emergency workers. Claire Calladine, a campaigner who runs the organisation 9/11 Health Now, said the fear was that the recent rise in cancer cases was just the start. "We have only seen the tip of the iceberg. How bad will it get - that is the big question."