Although a number of uncertainties remain to be addressed by continued research (NRC, 1998), a substantial body of published scientific literature recognizes a correlation between elevated PM concentrations and increased mortality rates.
There is still research being conducted.
The research has been completed.
A man is wearing purple performing a stunt.
A man throwing another man.
The person is holding a puppet.
Men lay down the train track.
I have reason to suspect that the girl at Manchester was merely a plant.
I have been doing this for around a decade.