Letters Section Editor: Robert M. Golub, MD, Senior Editor.
In Reply: Dr Thurston asks whether our approach could be used to investigate if achieving the newly proposed 24-hour average National Ambient Air Quality Standard for PM2.5 of 35 μg/m3 would eliminate the public health risk associated with short-term exposure to PM2.5. To address this question, we have reestimated the national average relative rates by using only data for days with PM2.5 levels of less than 35 μg/m3 and used the identical methods as reported in the article. The Table shows results using the entire data set from Table 1 of our article and from this restricted analysis. Despite the diminished statistical power, we still find statistically significant associations between short-term exposure to PM2.5 and hospital admissions for cerebrovascular disease, heart failure, and respiratory tract infections, as well as an association with heart rhythm (which was not significant in the original analysis). Although this is a post hoc analysis, these new results suggest that ambient levels of PM2.5 (even at levels below the current proposed 24-hour standard of 35 μg/m3) are associated with increased risk of hospitalization.
Dominici F, Peng RD, Bell ML, Pham L, McDermott A, Zeger SL, Samet JM. Hospital Admissions and Fine Particulate Air Pollution. JAMA. 2006;296(16):1966-1967. doi:10.1001/jama.296.16.1966-c