Benjamin G. Ferris

An association between air pollution and mortality in six U.S. cities

BACKGROUND Recent studies have reported associations between particulate air pollution and daily mortality rates. Population-based, cross-sectional studies of metropolitan areas in the United States have also found associations between particulate air pollution and annual mortality rates, but these studies have been criticized, in part because they did not directly control for cigarette smoking and other health risks. METHODS In this prospective cohort study, we estimated the effects of air pollution on mortality, while controlling for individual risk factors. Survival analysis, including Cox proportional-hazards regression modeling, was conducted with data from a 14-to-16-year mortality follow-up of 8111 adults in six U.S. cities. RESULTS Mortality rates were most strongly associated with cigarette smoking. After adjusting for smoking and other risk factors, we observed statistically significant and robust associations between air pollution and mortality. The adjusted mortality-rate ratio for the most polluted of the cities as compared with the least polluted was 1.26 (95 percent confidence interval, 1.08 to 1.47). Air pollution was positively associated with death from lung cancer and cardiopulmonary disease but not with death from other causes considered together. Mortality was most strongly associated with air pollution with fine particulates, including sulfates. CONCLUSIONS Although the effects of other, unmeasured risk factors cannot be excluded with certainty, these results suggest that fine-particulate air pollution, or a more complex pollution mixture associated with fine particulate matter, contributes to excess mortality in certain U.S. cities.

Long-term measurements of respirable sulfates and particles inside and outside homes

The results of extensive indoor and outdoor monitoring for respirable size particles and the sulfate fraction of these particles are reported. These air pollution measurements were obtained in conjunction with an epidemiologic study in six U.S. cities: Portage, Wisconsin; Topeka, Kansas; Kingston/Harriman, Tennessee; Watertown, Massachusetts; St. Louis, Missouri: and Steubenville, Ohio. The major source of indoor particulate matter is cigarette smoke, which contributes approximately 20 μm−3 to the indoor concentrations for each smoker. Even in homes without smokers, indoor particle concentrations equal or exceed outdoor levels. The indoor respirable sulfate concentrations are consistently lower than outdoor concentrations.

Daily diaries of respiratory symptoms and air pollution: methodological issues and results.

Daily diaries of respiratory symptoms are a powerful technique for detecting acute effects of air pollution exposure. While conceptually simple, these diary studies can be difficult to analyze. The daily symptom rates are highly correlated, even after adjustment for covariates, and this lack of independence must be considered in the analysis. Possible approaches include the use of incidence instead of prevalence rates and autoregressive models. Heterogeneity among subjects also induces dependencies in the data. These can be addressed by stratification and by two-stage models such as those developed by Korn and Whittemore. These approaches have been applied to two data sets: a cohort of school children participating in the Harvard Six Cities Study and a cohort of student nurses in Los Angeles. Both data sets provide evidence of autocorrelation and heterogeneity. Controlling for autocorrelation corrects the precision estimates, and because diary data are usually positively autocorrelated, this leads to larger variance estimates. Controlling for heterogeneity among subjects appears to increase the effect sizes for air pollution exposure. Preliminary results indicate associations between sulfur dioxide and cough incidence in children and between nitrogen dioxide and phlegm incidence in student nurses.

Exposure to Automobile Exhaust

The prevalence of chronic, nonspecific respiratory disease was assessed using a modified version of the Medical Research Council’s (MRC) respiratory disease questionnaire in a population of 268 policemen exposed to a spectrum of levels of automobile exhaust as traffic officers, patrol car officers, and indoor clerical officers. There were 99 men (36.9%) who fulfilled the usual criteria used with the MRC questionnaire for the diagnosis of disease. Data are presented to show that the men represent comparable groups and that smoking, and to a lesser extent traffic exposure, are associated factors in the development of disease. A summary of the environmental data is presented to indicate the kinds of exposure these men experience. Annual medical assessment and seasonal environmental assessments are planned to permit prospective evaluation of the effects of chronic exposure to automobile exhaust.

Mortality and morbidity in a pulp and a paper mill in the United States: a ten-year follow-up*

Two hundred and seventy-one men seen in 1963, who worked in a pulp and a paper mill, were followed up ten years later, in 1973. Death certificates were obtained for those who died. There did not appear to be any increased mortality in the group, nor was there any increased specific cause of death. A morbidity study of 200 men seen at both times did not show any differences in respiratory symptoms or prevalence of chronic non-specific respiratory disease. Analysis of pulmonary function showed little, if any, difference between groups. Analysis of retired, deceased, and still-working categories did suggest that exposures to Cl2 or SO2 might have a slight adverse effect on pulmonary function.

Pulmonary function in shipyard welders.

Sixty-one welders were studied at a shipyard by means of questionnaire, partial physical examination, x-ray films, and comprehensive tests of pulmonary function. Extensive air sampling was accomplished. The results were compared with 63 pipefitters similarly studied. There were no significant differences noted. St was noted, however, that both groups revealed evidence of depressed values of pulmonary function. By comparing welders to a third group (pipecoverers exposed to asbestos), evidence for the development of obstructive lung disease in welders and restrictive lung disease in pipecoverers arose, although nonsmoking welders appeared to have normal pulmonary function. When the shipyard groups were compared to pipefitters with no asbestos and no welding exposures, all shipyard groups were abnormal. Based on other prediction formulas, this finding remained consistent. It would thus appear that all three shipyard groups have depressed pulmonary function.

Low exposure to asbestos. Gas exchange in ship pipe coverers and controls.

In a previous survey of shipyard pipe coverers and controls, clinical criteria were used to define pulmonary asbestosis. This second survey focused on physiologic abnormalities. Pipe coverers had significantly reduced vital capacities (FVC) as well as single breath (DlSB) and exercise steady stale (DlSS-Ex) diffusing capacities. Resting steady state diffusing capacity (DlSS-R), fraction carbon monoxide removed (Fco), and the diffusing constant (K) differed from selected normals but not from all controls. Airways resistance, specific conductance, minute ventilation, arterial carbon dioxide pressure (Pco 2) and dead space were not significantly abnormal. Obstructive disease was equally common in both groups. All workers with clinical “asbestosls” also had severely reduced Dl and Fco. The significance of isolated reduction of Dlrequires further study. However, In a third survey three years later, Dl in exposed workers had deteriorated more rapidly than FVC; some with initially isolated reduction of Dl had de...

Adolescent height growth of US children

SummaryFeatures of adolescent height growth are characterized, using data from 6532 children, black and white, participating in the Harvard Six Cities Study from 1974 to 1989.

Prevalence of chronic respiratory disease. Asbestosis in ship repair workers.

Study of pipe coverers, pipe fitters, and welders at a ship repair yard indicated that pipe coverers had more changes in their lungs, as evidenced by examination of x-ray films, and slightly lower pulmonary function than the other two groups. All groups showed slightly lowered pulmonary function as compared with workers who did new-ship construction and were not exposed to asbestos. Aerometric measurement showed levels of asbestos that were, in general, lower than current threshold limit values. These findings reemphasize the need for control of asbestos in the work areas, as well as careful medical surveillance of workers exposed to asbestos.

Ventilatory function in workers exposed to low levels of toluene diisocyanate: a six-month follow-up

Peters, John M., Murphy, Raymond L. H., and Ferris, Benjamin, G., Jr. (1969).Brit. J. industr. Med.,26, 115-120. Ventilatory function in workers exposed to low levels of toluene diisocyanate: a six-month follow-up. Thirty-four workers exposed to toluene diisocyanate during production of polyurethane foam were examined with a respiratory questionnaire and tests of ventilatory capacity. The tests of pulmonary function were conducted on Monday morning and afternoon and on Tuesday morning and afternoon. Twenty-eight of these 34 workers had been examined with the same tests six months earlier. On Monday a mean change in the one-second forced expiratory volume (F.E.V.1·0) of –0·16 l. occurred that did not return to the baseline value (Monday a.m.) on Tuesday morning. A statistically significant decrease in all the measurements of ventilatory capacity except the forced vital capacity occurred over the six months in the 28 workers. The F.E.V.1·0 fell an average of 0·14 l. and flow rates at 75%, 50%, 25%, and 10% of vital capacity also decreased significantly. There was a highly significant correlation coefficient (r = 0·72) between one-day changes in F.E.V.1·0 (measured six months earlier) and six-month changes in F.E.V.1·0. Workers with respiratory symptoms (cough and/or phlegm) demonstrated greater falls in F.E.V.1·0 than did asymptomatic workers. All air concentrations of toluene diisocyanate measured during this study were below the threshold limit value (0·02 p.p.m.).