To adjust pollution globally, edit the config file:

\Manufactio\config\adpother\adpother.cfg

and adjust the following value:

    # Defines the global rate of emissions for all pollutants and sources on the server (in percents).
    I:globalEmissionRate=100

This is a percentage, and can be over 100.
Set to 0 to disable pollution emissions, set to 50 to reduce emissions by half.