Lung function in rescue workers at the World Trade Center after 7 years

Abstract

Background: The terrorist attacks on the World Trade Center on September 11, 2001, exposed thousands of Fire Department of New York City (FDNY) rescue workers to dust, leading to substantial declines in lung function in the first year. We sought to determine the longer-term effects of exposure.

Methods: Using linear mixed models, we analyzed the forced expiratory volume in 1 second (FEV(1)) of both active and retired FDNY rescue workers on the basis of spirometry routinely performed at intervals of 12 to 18 months from March 12, 2000, to September 11, 2008.

Results: Of the 13,954 FDNY workers who were present at the World Trade Center between September 11, 2001, and September 24, 2001, a total of 12,781 (91.6%) participated in this study, contributing 61,746 quality-screened spirometric measurements. The median follow-up was 6.1 years for firefighters and 6.4 years for emergency-medical-services (EMS) workers. In the first year, the mean FEV(1) decreased significantly for all workers, more for firefighters who had never smoked (a reduction of 439 ml; 95% confidence interval [CI], 408 to 471) than for EMS workers who had never smoked (a reduction of 267 ml; 95% CI, 263 to 271) (P<0.001 for both comparisons). There was little or no recovery in FEV(1) during the subsequent 6 years, with a mean annualized reduction in FEV(1) of 25 ml per year for firefighters and 40 ml per year for EMS workers. The proportion of workers who had never smoked and who had an FEV(1) below the lower limit of the normal range increased during the first year, from 3% to 18% for firefighters and from 12% to 22% for EMS workers, stabilizing at about 13% for firefighters and 22% for EMS workers during the subsequent 6 years.

Conclusions: Exposure to World Trade Center dust led to large declines in FEV(1) for FDNY rescue workers during the first year. Overall, these declines were persistent, without recovery over the next 6 years, leaving a substantial proportion of workers with abnormal lung function.

Figure 1. Firefighters and Emergency-Medical-Services (EMS) Workers Who Participated in the World Trade Center (WTC) Study

Shown are the numbers of firefighters and EMS workers who were employed by the Fire Department of New York City (FDNY) on September 11, 2001; those who were present at the WTC between September 11 and September 24, 2001; those who were active, retired, or deceased during each year after September 11, 2001; and the number of spirometric measurements that were performed. The numbers of retired or deceased workers are cumulative values. The numbers of active workers include those who were employed continuously from September 11, 2001 to the end of the indicated period. Spiro. msmts. denotes spirometric measurements.

Figure 2. Lung Function in Firefighters and Emergency-Medical-Services (EMS) Workers, According to Smoking Status

Panel A shows mean forced expiratory volume in 1 second (FEV₁) values (with adjustment for race, sex, height, and age on September 11, 2001 [9/11]) for Fire Department of New York City workers at the World Trade Center site from March 12, 2000, to September 11, 2008, according to smoking status. Panel B shows the percent of the predicted FEV₁ value for the same workers, according to the date of examination. Data are shown for white workers and black workers only, since reliable predicted normal values were not available for other groups. For firefighters, the median numbers of adjusted FEV₁ values that contributed to the estimated means for each 6-month interval were 132 for post-9/11 smokers, 650 for pre-9/11-only smokers, and 1882 for lifelong nonsmokers; for EMS workers, the median numbers were 123, 259, and 417, respectively. Since predicted FEV₁ values were available only for white workers and black workers, sample sizes were reduced by 3% for firefighters and 25% for EMS workers, as compared with the entire cohort. Standard errors of the estimated mean percent of the predicted FEV₁ values were always less than 2 percentage points for both firefighters and EMS workers.

Figure 3. Lung Function in Firefighters and Emergency-Medical-Services (EMS) Workers Who Had Never Smoked, According to Arrival Time at the World Trade Center

Panel A shows mean forced expiratory volume in 1 second (FEV₁) values (with adjustment for race, sex, height, and age on September 11, 2001 [9/11]) for non-smoking Fire Department of New York City workers from March 12, 2000, to September 11, 2008, according to the time of their arrival at the World Trade Center. Panel B shows the percent of the predicted FEV₁ value for the same workers. Data are shown for white workers and black workers only, since reliable predicted normal values were not available for other groups. For firefighters, the median numbers of adjusted FEV₁ values that contributed to the estimated means over each 6-month interval were 289 for firefighters who arrived on the morning of 9/11, 1443 for firefighters arriving later on 9/11 or the following day, and 114 for firefighters arriving on September 13 to September 24, 2001; for EMS workers, the median numbers were 74, 263, and 73, respectively. Since predicted FEV₁ values were available only for white workers and black workers, sample sizes were reduced by 3% for firefighters and 25% for EMS workers, as compared with the entire cohort. Standard errors of the estimated mean FEV₁ data were always less than 82 ml for firefighters and less than 74 ml for EMS workers. Standard errors of the estimated mean percent of the predicted FEV₁ were always less than 2 percentage points for both fire-fighters and EMS workers.

Figure 4. Abnormal Lung Function in Firefighters and Emergency-Medical-Services (EMS) Personnel Who Had Never Smoked and Who Worked at the World Trade Center Site during the First 2 Weeks after 9/11

Shown are data for nonsmoking Fire Department of New York City personnel who worked at the World Trade Center site during the first 2 weeks after the attack of September 11, 2001 (9/11). The proportions of firefighters and EMS workers who had a forced expiratory volume in 1 second (FEV₁) under the lower limit of the normal range (i.e., the lowest 5th percentile of a reference population) or less than 70% of the predicted value are indicated. Data are shown for white workers and black workers only, since reliable predicted normal values were not available for other groups. Median numbers of spirometric measurements per 6-month interval were 1822 for fire-fighters and 291 for EMS workers.