A team of researchers at Stony Brook University conducted a pilot study that suggests there may be a link between chronic post-traumatic stress disorder (PTSD) in 9/11 responders and cognitive degeneration, leading to diseases like Alzheimer’s.

Almost 16 years later and the deadly toxins that escaped on that horrific Sept. 11 day still linger in the bodies of the first responders who risked their health to help those in need.