anchor: To reflect concerns about the inherent limitations in the number of studies supporting a causal association between long-term exposure and mortality, an Alternative benefit estimate was derived from the large number of time-series studies that have established a likely causal relationship between short-term measures of PM and daily mortality statistics.
positive: The big number of time-series studies was used to create an Alternative benefit estimate.
negative: When every study was checked, there were no concerns about inherent limitations that indicated an association between long-term exposure and mortality.