complicating matters, emphysema deaths are often caused by pneumonia or cardiovascular disease, so ascertainment of emphysema deaths is not robust.
Respiratory mortality findings in several large-scale cohorts have been reported: American Cancer Society (ACS) (Pope et al. 1995, 2002), Six-Cities (Dockery et al. 1993), SDAs (Abbey et al. 1999), and Netherlands Cohort Study on Diet and Cancer (Hoek et al. 2002). Those studies, however, examined outcomes that are too broad to draw conclusions from, considering that they group composite ICD codes (for example, 460–519) under the broad labels “cardiopulmonary diseases”, “respiratory diseases”, and “non-malignant respiratory diseases.” A recent analysis of the ACS cohort (Pope et al. 2004) performed somewhat more diagnosis-specific analyses with the same methods as Pope et al. (2002). The RR of “COPD and allied conditions” (ICD codes 490–496) in relation to air-pollution exposure was not increased after adjusting for former and current smoking.
Garshick et al. (2003) studied US male veterans in Massachusetts (n=2,628) who resided near major roadways; such residence is an indicator of motor vehicle exhaust exposure. Veterans who lived within 50 meters of a major roadway were compared with those who lived more than 400 meters away. By virtue of their age (mean age 60.6 years), the veterans were not likely to be Gulf War veterans. They were drawn from the general population of southeastern Massachusetts, and they had not been treated in a VA medical center in the year before being surveyed. Estimates of individual exposure were based on current residential address (without information on residential history) linked to road type and traffic-count data in a geographic information system. Living near a major roadway appeared to be associated with increased reporting of persistent wheeze (OR 1.31, 95% CI 1.00–1.71), as did living near a major roadway with high traffic volume (over 10,000 vehicles per 24 hours) (OR 1.7, 95% CI 1.2–2.4), compared with living near a roadway with lower traffic volume. Self-reports of physician-diagnosed asthma or COPD (defined as chronic bronchitis or emphysema) were analyzed as confounders and effect modifiers. Associations were adjusted for cigarette-smoking, age, and occupational exposure to dust. The authors noted that limitations of the study include lack of information on duration of residence at each address and information about home exposure to NOx from cooking or heating. Information is lacking about the health effects of the nonresponders, because the study had a response rate of 58%.
Zhang et al. (1999) studied the effects of air pollution on respiratory health of adults in three Chinese cities. A study of parents of schoolchildren was performed on 4,108 adults who resided in four school districts of three major cities.4 Questionnaires adapted from the American Thoracic Society (ATS) Epidemiologic Standardization project were used to collect information on health status, occupation, level of education, smoking history, indoor air pollution in the home (coal use and smoking), history of respiratory illnesses, and symptoms. The self-reported symptoms ascertained were cough, phlegm, wheeze, and persistent cough and phlegm (PCP, an indicator of chronic bronchitis). Self-reported respiratory illnesses “ever diagnosed by a physician” were asthma and bronchitis, but the latter could have included acute or chronic bronchitis. Exposure to air pollution was determined on the basis of ambient air pollution data from monitoring stations in each district. Four-year average concentrations of TSP, SO2, and