One possibility is that studies report different estimates of the single true relationship between a given pollutant and a health effect due to differences in study design, random chance, or other factors.
The studies have various reports.
The reports are perfect.
A woman is hawking items for people in cars.
The young male is standing outdoors.
A dog and its owner stroll on the beach.
A woman has a bunch of bags
I know Borchardt is the most talented person on Earth.
A man is sitting on the ground outside.