Remarks on Ambient Air Pollution and Health Outcomes

Background. Ambient air pollution is a recognized risk factor for multiple health conditions. For some health problems, the impact of air pollution is particularly evident to the patients in a specific age range. Nonsimultaneous exposures to two or more air pollutants may have different relationships with health outcomes than do simultaneous exposures. Methods. Case-crossover technique was used to analyze data on emergency department (ED) visits for ischemic heart disease (IHD), epistaxis, and upper respiratory infection (URI). Conditional logistic regression models were used to estimate odds ratios and their 95% confidence intervals corresponding to an increase in an interquartile range of air pollutant concentrations. Results. The results for IHD show that for older patients (age 60+ years), the association between sulphur dioxide (SO2) exposure and IHD is weak. For ED visits for epistaxis (O3 and SO2 in one model) and URI (O3 and NO2 in one model), air pollutants lagged differently in the common model indicated significant statistical associations but not for common lags. Conclusion. The study findings, based on analyzed examples, suggest that (i) IHD cases in older age are less related to air pollution and (ii) air pollutants may affect some health conditions by a specific sequence of exposure occurrences. 1. Introduction Air pollution is a recognized risk factor for multiple health conditions, exacerbates disease states, and increases premature mortality [1–5]. In many epidemiological studies, age groups are defined a priori and, usually, persons of age greater than, say, 65 years of age (i.e., 65+) are considered and included in one group. It is an implicit assumption that air health effects are the same for all persons of this age and older. For some diseases, it may happen that in such a group the older persons are more affected by a preexisting disease itself rather than by an impact from environmental conditions. In this work, emergency department (ED) visits for ischemic heart disease (IHD) were considered in this context. The cases were identified using the ICD-9 codes 410–414 (the International Classification of Diseases, 9th Revision). The second example is related to the situation when two air pollutants considered in the same model show different associations with health outcomes. Thus, for two air pollutants, say X and Y, the configuration X (lag 0), Y (lag 0) may have a different association with the considered health endpoint than does the configuration X (lag 0), Y (lag 1). The air pollutants in the statistical model usually are