A man in a white shirt is walking a dog on the side of a street.
A man walks his dog down the street.
The Alternative Estimate of the impact of fine particle reductions on premature mortality relies on recent scientific studies finding an association between increased mortality and short-term (days to weeks) exposure to particulate matter, while the Base Estimate relies on a recent reanalysis of earlier studies that found associations between long-term exposure to fine particles and increased mortality.