Urban Exposures, Frailty, and Mental Illness in World Trade Center Health Program Responders

General responders of the World Trade Center (WTC) Health Program (WTCHP), who were uniquely exposed to chemical toxicants and extreme psychological stress during the 2001 terrorist attack, now experience a wide range of unusually prevalent health outcomes for a mid-aged population, including frailty, Post Traumatic Stress Disorder (PTSD), and depression.

We investigated whether these outcomes are associated with urban environmental exposures experienced in the two decades post 9/11.

Prospective cohort study.

WTCHP general responders' cohort.

We included 18,861 WTCHP general responders between the years 2003 to 2023 who took part in rescue, recovery, and clean-up tasks following the 9/11/2001 attack on the WTC.

We evaluated the distinct and combined associations with annual fine particulate matter (PM_2.5), temperature, and Green View Index (GVI) and assessed interactions with WTC-exposures.

We assessed frailty using a validated index developed specifically for the WTCHP. We determined PTSD and depression status based on repeated test scores from validated tools administered during the monitoring visits.

We included 18,861 responders, 81.89% were males, and the mean age at entry was 47. Interquartile range increases in PM_2.5 and temperature were significantly associated with increased frailty, PTSD, and depression scores, while greenness (GVI) was protective. A decile increase in the overall exposure mixture was associated with a 0.50% (95% confidence interval 0.08; 0.94) increase in frailty and a 0.10 unit (0.02; 0.18) increase in PTSD scores, primarily driven by temperature. Importantly, the exposure-mixture was associated with an increased risk of reaching a clinical threshold for PTSD (odds ratio: 1.013[1.001,1.024]). Finally, the associations between the exposure-mixture and mental health were significantly amplified among responders with high WTC-exposures, though no such modification was observed for frailty.

Exposures to heat and PM_2.5 were associated with increased frailty, PTSD, and depression, while greenness exposure was protective. Responders who experienced more intense WTC exposures were more vulnerable to later-life environmental exposure-mixture effects on mental health. These findings may help explain the elevated burden of these conditions among WTCHP responders and suggest avenues for public health interventions including education on risk mitigation strategies.