Exposure to dust in the aftermath of the World Trade Center attacks increased the risk of pulmonary fibrosis (PF) among responders, according to an evaluation of self-reported surveys. Researchers found that higher levels of dust exposure were associated with increased PF incidence.
The study, “Pulmonary Fibrosis among World Trade Center Responders: Results from the WTC Health Registry Cohort” was published in the International Journal of Environmental Research and Public Health.
The collapse of the World Trade Center (WTC) towers in a terrorist attack on Sept. 11, 2001, created a cloud of dust containing toxic substances. Some of these have been linked to PF development, including heavy metals such as titanium, silica, asbestos fibers, and wood dust.
About half the people who helped out in the aftermath of the attack were directly exposed to dust clouds. These included workers or volunteers (not affiliated with the New York fire department) who provided on-site rescue, cleanup, or support services after the attacks.
Previous studies have shown a link between exposure to WTC-site dust or fumes and various respiratory conditions or symptoms. Still, little is known about the impact of the dust derived from the WTC on PF, and the occurrence of the disease among WTC responders.
Now, a team of researchers assessed the relationship between WTC dust exposure and PF in responders, evaluating self-reported survey data from physicians’ PF diagnoses in the World Trade Center Health Registry.
The study included 19,300 WTC responders (77.8% men; median age 41), who were either self-identified through an outreach campaign (70%) or identified through government agencies, employer, or other entities (30%). All took part in an enrollment survey in 2003-2004, and three subsequent follow-ups (2006-2007, 2011-2012, and 2015-2016).
Among the participants analyzed, the team found 73 self-reported, physician-diagnosed PF cases, with a total incidence rate of 36.7 per 100,000 patient-years (the gathered amount of years all participants spent in the study). Of note, the most common type of PF (idiopathic pulmonary fibrosis; IPF) has an estimated incidence of 6.8-17.4 per 100,000 in the U.S.
Researchers then divided participants into four study groups depending on their exposure levels to dust at the site: low, medium, high, and very high.
Comparison among the different levels showed that PF incidence during follow-up increased with higher levels of dust exposure. About 2.5 times more participants in the medium and high groups were diagnosed with PF in the follow-up period, compared with the low-exposure group. The group exposed to very high levels of dust showed the most cases of PF (about 4.5 times more than the low- exposure group).
“The unique characteristics of WTC dust and its toxic components might explain our observed significant exposure-response effect of WTC dust exposure on PF among WTC responders,” the researchers stated.
The team also found that participants with PF showed a higher prevalence of physical and mental comorbidities, compared with participants without PF. Individuals with PF showed a significantly higher prevalence of mental comorbidities such as depression, post-traumatic stress disorder (PTSD), and anxiety. Physical comorbidities were also significantly higher in PF patients, including obstructive sleep apnea, chronic obstructive pulmonary disease (COPD), gastroesophageal reflux disease, and diabetes.
According to the team, these findings are consistent with existing literature.
“Despite the limitations, this study found evidence of the association between WTC dust and PF risk among WTC responders, adding evidence to the literature of occupational exposure and self-reported PF,” the researchers concluded. “Awareness and early detection of PF among at-risk 9/11-exposed populations may slow the progress of the condition by early intervention.”