Date Published: April 18, 2019
Publisher: Public Library of Science
Author(s): Eileen McNeely, Irina Mordukhovich, Steven Staffa, Samuel Tideman, Brent Coull, Alexander Larcombe.
Secondhand tobacco smoke (SHTS) is a tremendous public health hazard, leading to morbidity and premature mortality worldwide, with racial and ethnic minorities and those of lower socioeconomic status disproportionately affected. Flight attendants were historically exposed to high levels of SHTS in the aircraft cabin. The health effects of active smoking are known to persist for up to a lifetime, but the legacy effects of SHTS exposure have not been well characterized.
We aimed to evaluate the legacy health effects of occupational SHTS exposure among never smoking workers using the resources of the Harvard Flight Attendant Health Study, a large study of cabin crew health. We evaluated associations between SHTS exposure and a range of diagnoses using multivariate logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs), employing a case-control sampling method and applying the bootstrap method to increase accuracy and precision of results.
We found no evidence of positive associations between SHTS and any cancer, but observed associations between SHTS and cardiac outcomes, including myocardial infarction (OR = 140, 95% CI: 1·04, 3·27) and peripheral artery disease (OR = 1·27, 95% CI: 1·00, 1·97). We also found associations between SHTS exposure and repeated pneumonia (OR = 1·06, 95% CI: 1·02, 1·10).
Our study reports associations between legacy SHTS exposure going back decades and severe cardiac and respiratory health outcomes. Given the high prevalence of ongoing and historical SHTS exposure, our findings, if confirmed, have important implications for smoking cessation efforts, health education, and clinical guidelines.
Secondhand tobacco smoke (SHTS) is a tremendous public health hazard, leading to morbidity and premature mortality worldwide. Health effects of SHTS include lung cancer, cardiovascular disease (CVD), and impaired respiratory health [1–3]. Flight attendants were historically exposed to high levels of SHTS due to the past ubiquity of in-flight smoking, recirculated air and poor ventilation in the cabin, and an environment that increases respiratory stress through reduced oxygenation, elevated carbon dioxide, and low humidity . A 1986 report by the National Academy of Sciences found that full-time flight attendants were exposed to SHTS at levels equivalent to living with a pack-a-day smoker . When in-flight smoking was permitted, typical levels of respirable suspended particles violated current federal fine particulate matter standards threefold and exceeded irritation thresholds by ten to a hundred times, and SHTS exposure among cabin crew was six-fold that of the average U.S. worker and fourteen-fold that of the average U.S. resident .
We present participant characteristics in Table 1, overall and stratified by SHTS exposure status. Never-smoking participants presented with a mean age of 56 years, mean job tenure of 24 years, and mean BMI of 24 kg/m2, and most were female (83%) and white (86%). While we did not conduct formal tests for heterogeneity by exposure status, most characteristics were similar between the groups, except for age (61 vs 53 years) and tenure (34 vs 17 years). Characteristics of combined ever and never smokers were similar to that of the restricted sample (S1 Table). Only seven percent of our full sample were current smokers, while 34% were past smokers.
We report associations between legacy exposure to SHTS among never smoking workers and several health outcomes: MI, PAD, and repeated pneumonia. Our study is one of few to evaluate the legacy effects of workplace SHTS exposure, and to our knowledge is the most comprehensive study on this topic to date. Our findings are striking given the healthy worker effect, in which workers exhibit low morbidity because health is required to maintain employment, especially in demanding jobs , the low rates of obesity, hypertension and hypercholesteremia observed in our study [6,7], and the many years elapsed since implementation of smoking bans. Our results may be generalizable to other populations exposed to SHTS and, if confirmed, may inform clinical guidelines among people with such exposure histories regarding preventative health measures, screenings and health education even after many years of ceased exposure.
We report associations between legacy SHTS exposure going back decades and several severe cardiovascular and respiratory outcomes, including MI, PAD, and repeated pneumonia. SHTS is a preventable and modifiable exposure that continues to be a substantial cause of morbidity and premature death worldwide. Only 28 U.S. states have comprehensive public smoking bans and a large percentage of the world’s population is exposed to SHTS in the home, community, and workplace, with racial and ethnic minorities and those of lower socioeconomic status disproportionately affected . This represents a tremendous public health burden in light of severe and commonly occurring health outcomes, no known safe level of exposure , and the fact that we observed associations despite decades elapsing since implementation of in-flight smoking bans. Our findings, if confirmed, have implications for informing smoking cessation efforts, and clarifying health education and clinical guidelines among patients with SHTS exposure histories, even in the distant past.