The aftermath of the September 11 attacks have had profound and wide-ranging political, economic, health and societal effects. They also reshaped global security policies and international relations, prompting lasting changes in how nations address terrorism and collective safety. The attacks elicited major rescue and recovery efforts in the affected areas, in particular at the World Trade Center site, which was rebuilt to include a memorial to the victims. Many of the hundreds of workers assisting in these efforts, as well as survivors and people living and working near the site, became seriously ill in the following years and decades due to exposure to toxins, which had spread throughout New York City as a result of the Twin Towers’ collapse. Mental health problems, especially post-traumatic stress disorder (PTSD) among ordinary citizens and first responders also increased as a result of the attacks.