Assessment of recent ozone short-term epidemiologic studies

The U.S. Environmental Protection Agency (EPA) revised the National Ambient Air Quality Standards (NAAQS) for ozone in 1997 based largely on short-ter m ozone studies published up to 1995. The U.S. EPA's conclusions must now b e updated because (1) the agency did not consider many new studies publishe d since 1995 and (2) the agency did not critically review the studies publi shed before 1995 (i.e., it accepted the stated conclusions). in this articl e, we examine many recently published short-term ozone studies including 17 hospital admissions studies, 10 mortality studies, and 6 summer-camp studi es. Almost all of these studies reported a significant association between ambient levels of ozone and adverse health effects. However, on close exami nation, it is apparent that there are mixed findings from one study to anot her and even within the results of a single study. Moreover, questionable s tatistical analyses and failure to consider confounders make a number of th e reported findings doubtful and even negative.