By guest blogger Dr. David Prezant of the World Trade Center Medical Monitoring and Treatment Program and the Albert Einstein College of Medicine*
Can respirators be redesigned to “work” in this environment?
On September 11th, 2001, terrorist attacks led to the collapse of the World Trade Center. Approximately 70% of the buildings’ structural components were pulverized in the fiery collapse of these towers, including six million cubic feet of masonry, five million square feet of painted surfaces, seven million square feet of flooring, 600,000 cubic feet of window glass, 200 elevators, and all other items present in a modern office complex.1 It is estimated that hundreds of thousands of people were exposed, with the most highly exposed group being the rescue, recovery and cleanup workers.2,3 Pulverized building materials predominated in the initial period post-collapse, while combustion-derived pollutants increased as rescue, recovery and cleanup progressed.4 The fires at the site created toxic combustion products, such as polycyclic aromatic hydrocarbons (PAHs), dioxins, volatile organic compounds, and various other known carcinogenic compounds.1,4,5,6,7 Contaminants such as asbestos, hydrochloric acid, PCBs (Polychlorinated biphenyls), silica and heavy metals were found in the dust and ash resulting from the WTC collapse.1,4,5,6,7
The WTC Cough Syndrome (a chronic cough syndrome, thought to be a consequence of upper and lower respiratory disease typically including chronic asthmatic bronchitis, chronic rhinosinusitis, chronic gastroesophageal reflux, or any combination of the three) has been reported by a large percentage of the exposed. Rarely, there has also been evidence of interstitial lung disease, such as sarcoidosis, pulmonary fibrosis, and bronchiolitis obliterans. The WTC Cough Syndrome was first described in rescue workers from the Fire Department of the City of New York (FDNY).11 Higher rates of upper and lower respiratory irritant symptoms have also been described in at least seven WTC rescue/recovery worker groups including firefighter, police officer and other rescue/recovery and cleanup workers.12,13,16,17, 18,19,20,21 Respiratory consequences have also been noted in WTC studies on community residents, children & office workers in lower Manhattan.3,22,23,24
Pulmonary function declines or abnormalities have been significantly related to WTC exposure intensity (based on arrival time) in FDNY and non-FDNY workers. This remained true even after accounting for pre-existent disease and/or cigarette smoking.11,13,25,26,27,28,29 For 12,079 FDNY rescue workers in the first year post-WTC, a significantly greater average annual decline in forced expiratory volume in 1-second (FEV1) of 372 ml was noted in the first year post-9/11/01 when compared to the normal annual decline of 31 ml found in the 5-years of pre-WTC testing—a substantial accelerated decline in pulmonary function.3 Similar findings were found for the forced vital capacity (FVC). In the NY/NJ consortium report on 8,384 non-FDNY workers/volunteers, 28% had abnormal pulmonary function test results13. They also found that a low forced vital capacity (FVC, a measure of lung capacity) was 5 times more likely among the non-smoking portion of their cohort than expected in the general US population (which includes smokers and non-smokers).13 Studies in both cohorts (FDNY and non-FDNY) are currently underway to determine the course of pulmonary function over the next 5 years post-WTC, specifically, whether it has improved, stabilized or declined, and, if there are differences in clinical course within or between the cohorts, and which factors might be predictive of favorable or unfavorable outcome.
A clear exposure-response gradient has been found. Numerous studies have documented significant associations between increased respiratory symptoms, persistent airways hyperreactivity, RADS or asthma, and/or declines in pulmonary function with earlier WTC arrival times.2,11,12,16,17,18,19,20,25,26,27,28,29,33 A recent WTC registry study on newly diagnosed (post-9/11/01) asthma in rescue and recovery workers also showed an effect of cumulative exposure (especially greater than 90 hours) even after controlling for initial dust cloud exposure and early arrival time.33 Occurrences of WTC respiratory disease in rescue workers/volunteers whose first exposure was more than 48 hours post-collapse could be explained either by “high-level” exposures generated by activities that disturbed dust in place, while entering enclosed, poorly ventilated areas, or by the accumulation of repeated “low-level” exposures over time.
The WTC registry recently reported that for rescue/recovery workers who arrived on 9/11/01 and worked in all subsequent time periods (n=2,161), use of masks or respirators did not eliminate the risk for newly-diagnosed asthma; but that delays in the initial use of a mask or respirator were associated with an increased incidence of newly diagnosed asthma.33 This risk was substantial, with a delay of 1 week associated with at least a 60% increase and a delay of 16 or more weeks being associated with a two to three-fold increased risk in newly-diagnosed asthma. Even higher risk ratios were found when the population was restricted to firefighters and other search/rescue personnel, suggesting a greater or different exposure.
Ninety-five percent of the respirable WTC dust was composed of large particulate matter (≥10 microns in diameter).1 Particles of this size have conventionally been thought to be filtered by the upper respiratory tract, rarely entering the lower respiratory structures.4 However, there are a number of reasons to expect lower airways also to be at risk from the dust cloud. First, it has been shown that alkaline dust impairs nasal clearance mechanisms, and most WTC dust samples had a pH greater than 10 (very alkaline).14 Second, the nasal filtration system is optimally functional during restful breathing. However, WTC rescue/recovery workers, as a consequence of their work activities (moderate to high level physical exertion), were breathing at high minute ventilations where mouth breathing predominates. Third, although only five percent of the WTC dust was smaller than 10 microns in diameter, the extraordinary volume of dust in the air meant that the respirable fraction (particles less than 10 microns) represented a significant amount of exposure. Finally, although only a small percentage of particles larger than 10 microns tend to impact in lower airways, the huge magnitude of the WTC dust cloud meant that a small percentage of particles that penetrated deep into the lung may have added up to a significant exposure.15 In fact, in a study of 39 firefighters from the Fire Department of the City of New York (FDNY) 10 months after exposure,15 it was demonstrated the WTC dust did make it down into the lower airways, as particulate matter (>10microns) consistent with WTC dust, with associated increases in inflammatory cells and cytokines in induced sputum.
Respirators were not available early on and were not used consistently even when available.26 This is in sharp contrast to the estimated 1.3 million U.S. workplaces (labs, hospitals, etc.) where respirators are used daily to provide protection against various airborne hazards. But few if any of these workplaces are disaster sites with critically time-dependent rescue operations underway. Respirators require fit-testing and prior health clearance which is not often immediately available for disaster rescue workers. They are uncomfortable for prolonged use and do not allow for necessary communication between co-workers in this potentially unsafe work area in which coordination of the activities of work crews was essential. Thus, even when available, there are significant barriers to the use of respirators in a disaster environment, especially when rescue efforts are underway.
Given these barriers to use of respirators during rescue efforts at disaster sites, we pose the following questions:
- Are we certain that normal fit-testing procedures confirm that the respirator will fit correctly during moderate to heavy physical exertion?
- How can we assure protection while maximizing comfort – essential for reducing barriers to wearing a respirator?
- How can we assure protection, while maximizing the ability to communicate between workers, essential for maintaining safety in a hazardous environment?
- Will no fit-test respirators be available in the near future?
- What features of current respirator design need further improvement for this environment?
- How have users (first responders, construction workers) from disaster sites been involved in the past and how will they be involved in the future in testing new respirator designs?
- Do respirator manufacturers understand the needs of current and future users?
- Are there barriers that prevent respirator manufacturers from responding quickly to user needs?
- Are users looking for improvements for which technology does not yet exist?
—David Prezant, M.D.
Dr. Prezant is the Chief Medical Officer and Co-Director of the World Trade Center Medical Monitoring and Treatment Program in the New York City Fire Department and Professor of Medicine, Albert Einstein College of Medicine.