摘要:This paper presents some of the results from cross-sectional analyses and studies during air pollution alerts obtained as a part of the Six-City Study, a longitudinal study of the respiratory effects of air pollution. These analyses illustrate some of the limitations and uncertainties of epidemiologic studies. For example, an earlier report noted increased respiratory illness rates for children living in homes where gas was used for cooking. A later analysis did not confirm this. Reasons for this are explored by using different criteria and variables to be controlled for. The results illustrate that the strength of the association between cooking fuel and illness was sensitive to the definitions of the variables and the number of subjects and city cohorts. Similar examples are presented for illness rates for four respiratory diseases: asthma, bronchitis, illness before age 2 and illness last winter. These examples of cross-sectional analyses emphasize the ambiguities of studies of possible health effects of air pollution exposures close to the present ambient air quality standards. Full text Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (1.1M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References . 115 116 117 118 119 120 121 122 123