Air Pollution, the Automobile, and Public Health (1988) / Chapter Skim
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Epidemiologic Studies of Effects of Oxidant Exposure on Human Populations
Epidemiologic Studies of Effects of Oxidant Exposure on Human Populations
Pages 389-414
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From page 389... ...
BRESNITZ KATHLEEN M REST The Medical College of Pennsylvania Role of Epidemiology in Air Pollution Research / 390 Prior and Ongoing Studies Designs, Findings, and Problems / 390 Cross-Sectional Studies of Pulmonary Function and Symptoms / 391 Prospective Cohort Studies / 399 Retrospective Studies / 400 Generic Issues / 400 Exposure Assessment / 400 Effects Assessment / 401 Specific Issues and Study Approaches / 404 Chronic Obstructive Pulmonary Disease / 404 Asthma/Bronchial Hyperresponders / 405 Respiratory Infection / 407 Attributable Risk / 408 Summary / 409 Summary of Research Recommendations / 409 Specific Research Issues / 409 Generic Issues / 411 Air Pollution, the Automobile, and Public Health.
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From page 390... ...
, and long-term effects such as lung cancer and accelerated decline in lung function. Research on nonrespiratory effects has usually focused on nonoxidant exposures (for example, on lead, organic solvents, and carbon monoxide)
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From page 391... ...
In air pollution research, the outcomes under study may be correlated with serial measurements of ambient air pollutants. Parallel changes in the prevalence of symptoms or mean pulmonary function and average air pollutant levels would suggest an association between the exposure and the outcomes.
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From page 392... ...
· Temporal relationship between exposure and effect may be difficult to ascertain. effects that can be quantitated (e.g., pulmonary function)
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From page 393... ...
This cross-sectional study did well in adjusting for some variables that may confound or bias any apparent association between the level of ambient oxidants and the health outcome of interest. Unfortunately, the differences in the pulmonary function measurements were small and the likeli hood of detecting statistically significant differences in outcomes was correspondingly diminished.
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From page 394... ...
The age, gender, race, and income distributions were similar in the two cities. Daily maximum hourly concentrations of specific air pollutants were measured at stationary air monitoring stations.
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From page 395... ...
There are two general classes of potential confounders that must be considered in air pollution research: environmental confounders such as other air pollutants, occupational exposures, smoking, and meteorological variables; and personal confounders such as allergies and respiratory infections. The validity of any study is affected by the appropriate control of confounders, either in the design phase or the analysis phase of the study.
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From page 396... ...
Pollutant Study Description Results and Comments Reference 0.13a Oxidants 0.01-0.37 O3 Not reported O3 0.0000.235 O3 ( Table continued next page.) Daily records of times of onset and severity of asthma attacks of 137 asthmatics residing and working in Pasadena, California, between September 3 and December 9, 1956; daily maximum hourly average oxidant levels (KI)
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From page 397... ...
were monitored by LA-APCDs, 24-hr averages for TSP, RSP, SOx, NOX, SO2, and NO2 were monitored by the EPA, and meteorological conditions were monitored within 1 to 8 miles of homes in each community. Emergency room visits and hospital admissions for children with asthma symptoms during periods of high and low air pollution in Los Angeles from August 1979 to January 1980; daily maximum hourly concentrations of 03, S02, NO, NO2, HCs, and COH; weekly maximum hourly concentrations of SO42- and TSP; biweekly allergens and daily meterological variables from regional monitoring stations.
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From page 398... ...
NOTE: CHESS = Community Health Environmental Surveillance System; COH = coefficients of haze; HC = hydrocarbon; KI = potassium iodine method; LA-APCD = Los Angeles Air Pollution Control District; PM = particulate matter; RH = relative humidity; RSP = respirable suspended Articulates; TSP = total suspended Articulates. SOURCE: Adapted from U.S.
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From page 399... ...
The strength of this study lies in its excellent assessment of individual exposure and its effects, its careful definition of an asthmatic attack unique for each individual, and the quality of its statistical analysis. Nevertheless, that study and the other cross-sectional studies discussed here only suggest associations between increased levels of ambient oxidants and decrements in pulmonary function, higher prevalence of respiratory symptoms, and more frequent asthma attacks.
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From page 400... ...
Future epidemiologic studies of air pollution should include the use of retrospective methods to investigate the relationship between oxidant exposure and respiratory morbidity if more accurate methods of assessing past cumulative exposure can be developed. Generic Issues Exposure Assessment Estimating exposure, prospectively as well as retrospectively, is a difficult task.
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From page 401... ...
Valid and reliable questionnaires that help assess personal exposure to air pollutants should be developed and used in future epidemiologic studies. Elects Assessment Questionnaires and Diaries.
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From page 402... ...
Spirometry is the most practical test to assess pulmonary function and the one most often used in epidemiologic studies. Pulmonary function changes from predicted values are reflected in several parameters, including average absolute differ ences in flow rates and lung volumes, variation in rates of decline of flow rates, and increases in airway resistance and airway response to bronchoconstrictors.
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From page 403... ...
Data collected by the National Health and Nutrition Examination Survey, the National Health Interview Survey, health maintenance organizations, preferred provider organizations, and insurance companies are some examples of potentially useful data sources. A survey of existing data bases is needed to determine which are most likely to produce useful information on the health effects of air pollutants.
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From page 404... ...
The lack of a gold standard for diagnosing many respiratory illnesses makes the interpretation of studies that utilize these measures all the more difficult. Nevertheless, several investigators have utilized hospital data to assess the effects of air pollutants on respiratory morbidity (Sterling et al.
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Cross-Sectional Methods. Cross-sectional studies and secular trend analyses using the Medicaid data bases could also assess the prevalence of chronic respiratory disease and, perhaps, the frequency of various acute respiratory diseases in counties with different average levels of air pollutants.
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From page 406... ...
Recommendation 11. A variety of design methods should be used to study nonsmoking and smoking individuals with bronchial hyperresponsiveness to assess whether long-term residence in high-oxidant environments causes accelerated rates of decline in pulmonary function, more frequent encounters with the health care system, and increased severity of pulmonary symptoms.
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From page 407... ...
However, the studies cited in the review support the conclusion that a history compatible with lower respiratory infection is associated with impaired pulmonary function in children. This association may be causal or noncausal and may be mediated by a host factor such as atopy (allergy that is probably hereditary)
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From page 408... ...
More than one organism should be selected as a suspected respiratory pathogen to maximize the likelihood of detecting differences in infection rate among the cohorts. Attributable Risk Air pollution research efforts have focused primarily on acute effects in attempts to address issues of threshold effects, dose/response relationships, and disease incidence and prevalence in sensitive groups.
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From page 409... ...
measures of acute respiratory morbidity. Review of selected air pollution studies shows that higher oxidant exposures are associated with a higher prevalence of res piratory symptoms, more frequent asthma attacks, greater decreases from expected pulmonary function, and more frequent utilization of health care services.
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Recommendlation2 Future epidemiologic studies of air pollution should include the use of retrospective methods to investigate the relationship between oxidant exposure and respiratory morbidity if accu ~ 1 rate methods of assessing past cumulative exposure can be developed. Recommendation 9 Investigators should do case-control studies using existing health service data bases to assess the relationship between specific diseases and long-term residence in high-pollution areas.
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From page 411... ...
Recommendation 3 Future epidemiologic studies should use personal monitors and a greater number of better-placed area monitors to improve the assessment of true exposure in at least a sample of the individuals under study. Recommendation 4 Valid and reliable questionnaires that help assess personal expo sure to air pollutants should be developed and used in future epidemiologic studies.
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From page 412... ...
1979. The UCLA population studies of chronic obstructive respiratory disease.
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From page 413... ...
III. Comparison of pulmonary function in three communities exposed to photochemical oxidants, multiple primary pollutants, or minimal pollutants, Chest 78:252-262.
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