Toxic dust legacy plagues thousands of 9/11 survivors
More than 18,000 people are suffering from illnesses linked to the dust from the attacks on New York's World Trade Centre on 11 September 2001.
The figure comes from the US government's monitoring and treatment programme for 9/11 emergency workers, volunteers and local residents.
The most common afflictions are respiratory problems including asthma and sinusitis, but muscular and intestinal conditions are reported as well.
The senior US official managing the health legacy of the attacks warns that early deaths are possible among the survivors.
David Shukman reports