World Trade Center Health Program
On September 11, 2001, 19 terrorists associated with the Islamist militant group al-Qaeda hijacked four passenger jets in a series of suicide attacks on the United States, killing 2,996 people and injuring more than 6,000 others. Hijackers flew planes into two main towers of the World Trade Center, resulting in the collapse of three buildings of the World Trade Center complex, and the Pentagon, resulting in the partial destruction of the western side in the building. The resulting dust cloud due to the collapse of the World Trade Center covered Manhattan for days and contained thousands of tons of toxic debris, including asbestos and other known carcinogens. Another hijacked plane crashed into a field in Shanksville, Pennsylvania following an attempt by the passengers to retake control of the plane. No one in the airliners survived.
As of 2011, approximately 18,000 people have received medical treatment for illnesses related to toxic dust from the World Trade Center site. A study of rescue workers released in April 2010 found that all those studied had impaired lung functions, and that 30–40% were reporting little or no improvement in persistent symptoms that started within the first year of the attack. In 2011 a major research study showed significant long term medical and psychological effects among first responders to the World Trade Center site. These effects include elevated levels of asthma, sinusitis, Gastroesophageal reflux disease and posttraumatic stress disorder.
9/11 Commission Report
In addition to identifying intelligence failures occurring before the attacks, the report provided evidence of the following:The commission also concluded 15 of the 19 hijackers who carried out the attacks were from Saudi Arabia, but the commission "found no evidence that the Saudi government as an institution or senior Saudi officials individually funded the organization" to conspire in the attacks, or that it funded the attackers even though the "report identifies Saudi Arabia as the primary source of al-Qaeda funding". (A 28-page section of an earlier, different 9/11 report included claims of greater Saudi involvement, but "did not withstand deeper scrutiny" by the Commission.)
Mohamed Atta, the leader of the attacks, was from Egypt. Two hijackers were from the United Arab Emirates, and one was from Lebanon. According to the commission, all 19 hijackers were members of the al-Qaeda terrorist organization, led by Osama bin Laden. In addition, while meetings between al-Qaeda representatives and Iraqi government officials had taken place, the panel had no credible evidence that Saddam Hussein had assisted al-Qaeda in preparing or executing the 9/11 attacks.